Shape of Pion Distribution Amplitude
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, Anatoly
2009-11-01
A scenario is investigated in which the leading-twist pion distribution amplitude $\\varphi_\\pi (x)$ is approximated by the pion decay constant $f_\\pi$ for all essential values of the light-cone fraction $x$. A model for the light-front wave function $\\Psi (x, k_\\perp)$ is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination $ k_\\perp^2/x(1-x)$. It is shown that this model easily reproduces the fit of recent large-$Q^2$ BaBar data on the photon-pion transition form factor. Some aspects of scenario with flat pion distribution amplitude are discussed.
Determination of the pion distribution amplitude
Huang, Tao; Wu, Xing-Gang
2013-01-01
Right now, we have not enough knowledge to determine the hadron distribution amplitudes (DAs) which are universal physical quantities in the high energy processes involving hadron for applying pQCD to exclusive processes. Even for the simplest pion, one can't discriminate from different DA models. Inversely, one expects that processes involving pion can in principle provide strong constraints on the pion DA. For example, the pion-photon transition form factor (TFF) can get accurate information of the pion wave function or DA, due to the single pion in this process. However, the data from Belle and BABAR have a big difference on TFF in high $Q^2$ regions, at present, they are helpless for determining the pion DA. At the present paper, we think it is still possible to determine the pion DA as long as we perform a combined analysis of the most existing data of the processes involving pion such as $\\pi \\to \\mu \\bar{\
In-Medium Pion Valence Distribution Amplitude
Tsushima, K
2016-01-01
After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
In-Medium Pion Valence Distribution Amplitude
Tsushima, K.; de Melo, J. P. B. C.
2017-03-01
After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
Pion Distribution Amplitude from Lattice QCD
Braun, V M; Göckeler, M; Pérez-Rubio, P; Schäfer, A; Schiel, R W; Sternbeck, A
2015-01-01
We have calculated the second moment of the pion light-cone distribution amplitude using two flavors of dynamical (clover) fermions on lattices of different volumes, lattice spacings between $0.06 \\, \\mathrm {fm}$ and $0.08 \\, \\mathrm {fm}$ and pion masses down to $m_\\pi\\sim 150 \\, \\mathrm {MeV}$. Our result for the second Gegenbauer coefficient is $a_2 = 0.1364(154)(145)$ and for the width parameter $\\langle \\xi^2 \\rangle = 0.2361(41)(39)$. Both numbers refer to the scale $\\mu=2 \\, \\mathrm {GeV}$in the $\\overline{\\text{MS}}$ scheme, the first error is statistical including the uncertainty of the chiral extrapolation, and the second error is the estimated uncertainty coming from the nonperturbatively determined renormalization factors.
Exclusive processes in position space and the pion distribution amplitude
Braun, Vladimir M.; Müller, Dieter
2007-01-01
We suggest to carry out lattice calculations of current correlators in position space, sandwiched between the vacuum and a hadron state (e.g. pion), in order to access hadronic light-cone distribution amplitudes (DAs). In this way the renormalization problem for composite lattice operators is avoided altogether, and the connection to the DA is done using perturbation theory in the continuum. As an example, the correlation function of two electromagnetic currents is calculated to the next-to-n...
Photon-to-pion transition form factor and pion distribution amplitude from holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Zuo, Fen [Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China); Chinese Academy of Sciences, Theoretical Physics Research Center for Science Facilities, Beijing (China); Istituto Nazionale di Fisica Nucleare, Secione di Bari, Bari (Italy); Huang, Tao [Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China); Chinese Academy of Sciences, Theoretical Physics Research Center for Science Facilities, Beijing (China)
2012-01-15
We try to understand the recently observed anomalous behavior of the photon-to-pion transition form factor in the holographic QCD approach. First the holographic description of the anomalous {gamma}{sup *}{gamma}{sup *}{pi}{sup 0} form factor is reviewed and applied to various models. It is pointed out that the holographic identification of the pion mode from the 5D gauge field strength rather than the gauge potential, as first made by Sakai and Sugimoto, naturally reproduces the scaling behavior of various pion form factors. It is also illustrated that in describing the anomalous form factor, the holographic approach is asymptotically dual to the perturbative QCD (pQCD) framework, with the pion mode {pi}(z){proportional_to}z corresponding to the asymptotic pion distribution amplitude. This indicates some inconsistency in light-front holography, since {pi}(z){proportional_to}z would be dual to {phi}(x){proportional_to}{radical}(x(1-x)) there. This apparently contradictory can be attributed to the fact that the holographic wave functions are effective ones, as observed early by Radyushkin. After clarifying these subtleties, we employ the relation between the holographic and the perturbative expressions to study possible asymptotic violation of the transition form factor. It is found that if one require that the asymptotic form factor possess a pQCD-like expression, the pion mode can only be ultraviolet-enhanced by logarithmic factors. The minimally deformed pion mode will then be of the form {pi}(z){proportional_to}zln(z{lambda}){sup -1}. We suppose that this deformation may be due to the coupling of the pion with a nontrivial open string tachyon field, and then the parameter {lambda} will be related to the quark condensate. Interestingly, this pion mode leads immediately to Radyushkin's logarithmic model, which fitted very well the experimental data in the large-Q{sup 2} region. On the other side, the pQCD interpretation with a flat-like pion distribution
Pion distribution amplitude from holographic QCD and the electromagnetic form factor F_pi(Q2)
Agaev, S S
2008-01-01
The holographic QCD prediction for the pion distribution amplitude (DA) $\\phi_{hol}(u)$ is used to compute the pion spacelike electromagnetic form factor $F_{\\pi}(Q^2)$ within the QCD light-cone sum rule method. In calculations the pion's renormalon-based model twist-4 DA, as well as the asymptotic twist-4 DA are employed. Obtained theoretical predictions are compared with experimental data and with results of the holographic QCD.
The Pion-Photon Transition Distribution Amplitudes in the Nambu-Jona Lasinio Model
Courtoy, A
2007-01-01
We define the pion-photon Transition Distribution Amplitudes (TDA) in a field theoretic formalism from a covariant Bethe-Salpeter approach for the determination of the bound state. We apply our formalism to the Nambu - Jona Lasinio model, as a realistic theory of the pion. The obtained vector and axial TDAs satisfy all features required by general considerations. In particular, sum rules and polynomiality condition are explicitly verified. We have numerically proved that the odd coefficients in the polynomiality expansion of the vector TDA vanish in the chiral limit. The role of PCAC and the presence of a pion pole are explicitly showed.
Virtuality and Transverse Momentum Dependence of Pion Distribution Amplitude
Radyushkin, A V
2015-01-01
We describe basics of a new approach to transverse momentum dependence in hard exclusive processes. We develop it in application to the transition process \\gamma^* \\gamma -> \\pi^0 at the handbag level. Our starting point is coordinate representation for matrix elements of operators (in the simplest case, bilocal O (0,z) ) describing a hadron with momentum p. Treated as functions of (pz) and z^2, they are parametrized through virtuality distribution amplitudes (VDA) \\Phi (x, \\sigma), with x being Fourier-conjugate to (pz) and \\sigma Laplace-conjugate to z^2. For intervals with z^+=0, we introduce the transverse momentum distribution amplitude (TMDA) \\Psi (x, k_\\perp), and write it in terms of VDA \\Phi (x, \\sigma). The results of covariant calculations, written in terms of \\Phi (x, \\sigma) are converted into expressions involving \\Psi (x, k_\\perp). Starting with scalar toy models, we extend the analysis onto the case of spin-1/2 quarks and QCD. We propose simple models for soft VDAs/TMDAs, and use them for comp...
Chimera distribution amplitudes for the pion and the longitudinally polarized ρ-meson
Energy Technology Data Exchange (ETDEWEB)
Stefanis, N.G., E-mail: stefanis@tp2.ruhr-uni-bochum.de [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Pimikov, A.V., E-mail: pimikov@theor.jinr.ru [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, 730000 (China)
2016-01-15
Using QCD sum rules with nonlocal condensates, we show that the distribution amplitude of the longitudinally polarized ρ-meson may have a shorttailed platykurtic profile in close analogy to our recently proposed platykurtic distribution amplitude for the pion. Such a chimera distribution de facto amalgamates the broad unimodal profile of the distribution amplitude, obtained with a Dyson–Schwinger equations-based computational scheme, with the suppressed tails characterizing the bimodal distribution amplitudes derived from QCD sum rules with nonlocal condensates. We argue that pattern formation, emerging from the collective synchronization of coupled oscillators, can provide a single theoretical scaffolding to study unimodal and bimodal distribution amplitudes of light mesons without recourse to particular computational schemes and the reasons for them.
Chimera distribution amplitudes for the pion and the longitudinally polarized $\\rho$-meson
Stefanis, N G
2016-01-01
Using QCD sum rules with nonlocal condensates, we show that the distribution amplitude of the longitudinally polarized $\\rho$-meson may have a shorttailed platykurtic profile in close analogy to our recently proposed platykurtic distribution amplitude for the pion. Such a chimera distribution de facto amalgamates the broad unimodal profile of the distribution amplitude, obtained with a Dyson-Schwinger equations-based computational scheme, with the suppressed tails characterizing the bimodal distribution amplitudes derived from QCD sum rules with nonlocal condensates. We argue that pattern formation, emerging from the collective synchronization of coupled oscillators, can provide a single theoretical scaffolding to study unimodal and bimodal distribution amplitudes of light mesons without recourse to particular computational schemes and the reasons for them.
Twist-3 Distribution Amplitudes of Pion in the Light-Front Quark Model
Choi, Ho-Meoyng
2016-01-01
We analyzed two twist-3 distribution amplitudes of pion, i.e. pseudoscalar $\\phi^P_{3;\\pi}(x)$ and pseudotensor $\\phi^\\sigma_{3;\\pi}(x)$, within the LFQM. Our LFQM descriptions both for twist-3 $\\phi^P_{3;\\pi}$ and $\\phi^\\sigma_{3;\\pi}$ not only satisfy the fundamental constraint required from the isospin symmetry, but also reproduce exactly the asymptotic forms anticipated from QCD's conformal limit.
A consistent model for \\pi N transition distribution amplitudes and backward pion electroproduction
Lansberg, J P; Semenov-Tian-Shansky, K; Szymanowski, L
2011-01-01
The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state. We present a general framework for modelling nucleon to pion ($\\pi N$) TDAs. Our main tool is the spectral representation for \\pi N TDAs in terms of quadruple distributions. We propose a factorized Ansatz for quadruple distributions with input from the soft-pion theorem for \\pi N TDAs. The spectral representation is complemented with a D-term like contribution from the nucleon exchange in the cross channel. We then study backward pion electroproduction in the QCD collinear factorization approach in which the non-perturbative part of the amplitude involves \\pi N TDAs. Within our two component model for \\pi N TDAs we update previous leading-twist estimates of the unpolarized cross section. Finally, we compute the transverse target single spin asymmetry as a fu...
Revisiting the Pion Leading-Twist Distribution Amplitude within the QCD Background Field Theory
Zhong, Tao; Wang, Zhi-Gang; Huang, Tao; Fu, Hai-Bing; Han, Hua-Yong
2014-01-01
We study the pion leading-twist distribution amplitude (DA) within the framework of SVZ sum rules under the background field theory. To improve the accuracy of the sum rules, we expand both the quark propagator and the vertex $(z\\cdot \\tensor{D})^n$ of the correlator up to dimension-six operators in the background field theory. The sum rules for the pion DA moments are obtained, in which all condensates up to dimension-six have been taken into consideration. Using the sum rules, we obtain $\\left|_{\\rm 1\\;GeV} = 0.338 \\pm 0.032$, $\\left|_{\\rm 1\\;GeV} = 0.211 \\pm 0.030$ and $\\left|_{\\rm 1\\;GeV} = 0.163 \\pm 0.030$. It is shown that the dimension-six condensates shall provide sizable contributions to the pion DA moments. We show that the first Gegenbauer moment of the pion leading-twist DA is $a^\\pi_2|_{\\rm 1\\;GeV} = 0.403 \\pm 0.093$, which is consistent with those obtained in the literature within errors but prefers a larger central value as indicated by lattice QCD predictions.
Second Moment of the Pion Light-cone Distribution Amplitude from Lattice QCD
Braun, V M; Göckeler, M; Pérez-Rubio, P; Schäfer, A; Schiel, R W; Sternbeck, A
2015-01-01
We present the results of a lattice study of the second moment of the light-cone pion distribution amplitude using two flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to $m_\\pi\\sim 150 \\, \\mathrm {MeV}$. At lattice spacings between $0.06 \\, \\mathrm {fm}$ and $0.08 \\, \\mathrm {fm}$ we find for the second Gegenbauer moment the value $a_2 = 0.1364(154)(145)$ at the scale $\\mu=2 \\, \\mathrm {GeV}$ in the $\\overline{\\mathrm{MS}}$ scheme, where the first error is statistical including the uncertainty of the chiral extrapolation, and the second error is the estimated uncertainty coming from the nonperturbatively determined renormalization factors.
Pion-to-photon transition distribution amplitudes in the non-local chiral quark model
Kotko, Piotr
2008-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDA's. We note only residual dependence on the precise form of the cut-off function, however vector TDA that is symmetric in skewedness parameter in the local quark model is no longer symmetric in the non-local case. We calculate also the transition form-factors and compare them with existing experimental parametrizations.
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, Anatoly V. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States)
2016-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion {\\it transverse momentum distribution amplitude} (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asymptotic pQCD predictions and show that in the $Q^2 \\lesssim 10$ GeV$^2$ region there is essentially no sensitivity to the shape of the pion distribution amplitude. Furthermore, the magnitude of the one-gluon exchange contribution in this region is estimated to be an order of magnitude below the Jefferson Lab data, thus leaving the Feynman mechanism as the only one relevant to the pion electromagnetic form factor behavior for accessible $Q^2$.
Amplitude analysis of resonant production in three pions
Jackura, Andrew; Szczepaniak, Adam
2016-01-01
We present some results on the analysis of three pion resonances. The analyses are motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. We construct reaction amplitudes that satisfy fundamental $S$-matrix principles, which allows the use of models that have physical constraints to be used in fitting data. The models are motivated by the isobar model that satisfy unitarity constraints. The model consist of a Deck production amplitude with which final state interactions are constrained by unitarity. We employ the isobar model where two of the pions form a quasi-stable particle. The analysis is performed in the high-energy, single Regge limit. We specifically discuss the examples of the three pion $J^{PC}=2^{-+}$ resonance in the $\\rho\\pi$ and $f_2\\pi$ channels.
Amplitude analysis of resonant production in three pions
Directory of Open Access Journals (Sweden)
Jackura Andrew
2016-01-01
Full Text Available We present some results on the analysis of three pion resonances. The analyses are motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. We construct reaction amplitudes that satisfy fundamental S -matrix principles, which allows the use of models that have physical constraints to be used in fitting data. The models are motivated by the isobar model that satisfy unitarity constraints. The model consist of a Deck production amplitude with which final state interactions are constrained by unitarity. We employ the isobar model where two of the pions form a quasi-stable particle. The analysis is performed in the high-energy, single Regge limit. We specifically discuss the examples of the three pion JPC = 2−+ resonance in the ρπ and f2π channels.
Amplitude analysis of resonant production in three pions
Jackura, Andrew; Mikhasenko, Mikhail; Szczepaniak, Adam
2016-11-01
We present some results on the analysis of three pion resonances. The analyses are motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. We construct reaction amplitudes that satisfy fundamental S -matrix principles, which allows the use of models that have physical constraints to be used in fitting data. The models are motivated by the isobar model that satisfy unitarity constraints. The model consist of a Deck production amplitude with which final state interactions are constrained by unitarity. We employ the isobar model where two of the pions form a quasi-stable particle. The analysis is performed in the high-energy, single Regge limit. We specifically discuss the examples of the three pion JPC = 2-+ resonance in the ρπ and f2π channels.
Amplitude analysis of resonant production in three pions
Energy Technology Data Exchange (ETDEWEB)
Jackura, Andrew [Indiana Univ., Bloomington, IN (United States); Mikhasenko, Mikhail [Univ. of Bonn (Germany); Szczepaniak, Adam [Indiana Univ., Bloomington, IN (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-11-29
We present some results on the analysis of three pion resonances. The analyses are motivated by the recent release of the largest data set on diffractively produced three pions by the COMPASS collaboration. We construct reaction amplitudes that satisfy fundamental $S$-matrix principles, which allows the use of models that have physical constraints to be used in fitting data. The models are motivated by the isobar model that satisfy unitarity constraints. The model consist of a Deck production amplitude with which final state interactions are constrained by unitarity. We employ the isobar model where two of the pions form a quasi-stable particle. The analysis is performed in the high-energy, single Regge limit. We specifically discuss the examples of the three pion $J^{PC}=2^{-+}$ resonance in the $\\rho\\pi$ and $f_2\\pi$ channels.
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Radyushkin, A V
2015-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion transverse momentum distribution amplitude (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asympt...
Sketching the pion's valence-quark generalised parton distribution
Directory of Open Access Journals (Sweden)
C. Mezrag
2015-02-01
Full Text Available In order to learn effectively from measurements of generalised parton distributions (GPDs, it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL truncation of QCD's Dyson–Schwinger equations and exemplified via the pion's valence dressed-quark GPD, Hπv(x,ξ,t. Our analysis focuses primarily on ξ=0, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting Hπv(x,ξ=±1,t with the pion's valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for Hπv(x,0,t, expressed as the Radon transform of a single amplitude. Therewith we obtain results for Hπv(x,0,t and the associated impact-parameter dependent distribution, qπv(x,|b→⊥|, which provide a qualitatively sound picture of the pion's dressed-quark structure at a hadronic scale. We evolve the distributions to a scale ζ=2 GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.
Pion valence-quark parton distribution function
Directory of Open Access Journals (Sweden)
Lei Chang
2015-10-01
Full Text Available Within the Dyson–Schwinger equation formulation of QCD, a rainbow ladder truncation is used to calculate the pion valence-quark distribution function (PDF. The gap equation is renormalized at a typical hadronic scale, of order 0.5 GeV, which is also set as the default initial scale for the pion PDF. We implement a corrected leading-order expression for the PDF which ensures that the valence-quarks carry all of the pion's light-front momentum at the initial scale. The scaling behavior of the pion PDF at a typical partonic scale of order 5.2 GeV is found to be (1−xν, with ν≃1.6, as x approaches one.
Nucleon and $N^* (1535)$ Distribution Amplitudes
Braun, V M; Göckeler, M; Hagen, C; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schäfer, A; Schiel, R W; Schierholz, G; Stüben, H; Zanotti, J M
2010-01-01
The QCDSF collaboration has investigated the distribution amplitudes and wavefunction normalization constants of the nucleon and its parity partner, the $N^* (1535)$. We report on recent progress in the calculation of these quantities on configurations with two dynamical flavors of $\\mathcal{O}(a)$-improved Wilson fermions. New data at pion masses of approximately 270 MeV helps in significantly reducing errors in the extrapolation to the physical point.
Light Meson Distribution Amplitudes
Arthur, R.; Brommel, D.; Donnellan, M.A.; Flynn, J.M.; Juttner, A.; de Lima, H.Pedroso; Rae, T.D.; Sachrajda, C.T.; Samways, B.
2010-01-01
We calculated the first two moments of the light-cone distribution amplitudes for the pseudoscalar mesons ($\\pi$ and $K$) and the longitudinally polarised vector mesons ($\\rho$, $K^*$ and $\\phi$) as part of the UKQCD and RBC collaborations' $N_f=2+1$ domain-wall fermion phenomenology programme. These quantities were obtained with a good precision and, in particular, the expected effects of $SU(3)$-flavour symmetry breaking were observed. Operators were renormalised non-perturbatively and extrapolations to the physical point were made, guided by leading order chiral perturbation theory. The main results presented are for two volumes, $16^3\\times 32$ and $24^3\\times 64$, with a common lattice spacing. Preliminary results for a lattice with a finer lattice spacing, $32^3\\times64$, are discussed and a first look is taken at the use of twisted boundary conditions to extract distribution amplitudes.
Sketching the pion's valence-quark generalised parton distribution
Mezrag, C; Moutarde, H; Roberts, C D; Rodriguez-Quintero, J; Sabatie, F; Schmidt, S M
2014-01-01
In order to learn effectively from measurements of generalised parton distributions (GPDs), it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD, $H_\\pi^{\\rm v}(x,\\xi,t)$. Our analysis focuses primarily on $\\xi=0$, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting $H_\\pi^{\\rm v}(x,\\xi=\\pm 1,t)$ with the pion's valence-quark parton distribution amplitude. We explain that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for $H_\\pi^{\\rm v}(x,0,t)$, expressed as th...
Modeling the pion Generalized Parton Distribution
Mezrag, C
2015-01-01
We compute the pion Generalized Parton Distribution (GPD) in a valence dressed quarks approach. We model the Mellin moments of the GPD using Ans\\"atze for Green functions inspired by the numerical solutions of the Dyson-Schwinger Equations (DSE) and the Bethe-Salpeter Equation (BSE). Then, the GPD is reconstructed from its Mellin moment using the Double Distribution (DD) formalism. The agreement with available experimental data is very good.
PULSE AMPLITUDE DISTRIBUTION RECORDER
Cowper, G.
1958-08-12
A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.
Zhong, Tao; Wu, Xing-Gang; Huang, Tao
2016-07-01
The low-energy and high-energy behavior of the pion-photon transition form factor F_{π γ }(Q^2) are sensitive to the transverse and longitudinal distributions of the pion wave function, respectively. A careful study of F_{π γ }(Q^2) shall thus provide helpful constraints on the properties of the pion wave function. In this paper, we present a combined analysis of the data on F_{π γ }(Q^2) reported by the CELLO, the CLEO, the BABAR, and the BELLE Collaborations. It is performed by using the method of least squares. By using the combined measurements of the BELLE and CLEO Collaborations, the pion wave function longitudinal and transverse behavior can be fixed to a certain degree, i.e. we obtain β in [0.691,0.757] GeV and B in [0.00,0.235] for P_{χ ^2} ≥ 90 %, where β and B are two parameters of a convenient pion wave function model. It is noted that the distribution amplitude of such a pion wave function can mimic various longitudinal behaviors, as suggested in the literature under a proper choice of parameters. We observe that the CELLO, CLEO, and BELLE data are consistent with each other, all of which prefer the asymptotic-like distribution amplitude; while the BABAR data prefers a more broad distribution amplitude, such as the CZ-like one.
Pion generalized parton distributions within a fully covariant constituent quark model
Energy Technology Data Exchange (ETDEWEB)
Fanelli, Cristiano [Massachusetts Institute of Technology, Cambridge, MA (United States). Lab. for Nuclear Science; Pace, Emanuele [' ' Tor Vergata' ' Univ., Rome (Italy). Physics Dept.; INFN Sezione di TorVergata, Rome (Italy); Romanelli, Giovanni [Rutherford-Appleton Laboratory, Didcot (United Kingdom). STFC; Salme, Giovanni [Istituto Nazionale di Fisica Nucleare, Rome (Italy); Salmistraro, Marco [Rome La Sapienza Univ. (Italy). Physics Dept.; I.I.S. G. De Sanctis, Rome (Italy)
2016-05-15
We extend the investigation of the generalized parton distribution for a charged pion within a fully covariant constituent quark model, in two respects: (1) calculating the tensor distribution and (2) adding the treatment of the evolution, needed for achieving a meaningful comparison with both the experimental parton distribution and the lattice evaluation of the so-called generalized form factors. Distinct features of our phenomenological covariant quark model are: (1) a 4D Ansatz for the pion Bethe-Salpeter amplitude, to be used in the Mandelstam formula for matrix elements of the relevant current operators, and (2) only two parameters, namely a quark mass assumed to be m{sub q} = 220 MeV and a free parameter fixed through the value of the pion decay constant. The possibility of increasing the dynamical content of our covariant constituent quark model is briefly discussed in the context of the Nakanishi integral representation of the Bethe-Salpeter amplitude. (orig.)
Kim, Changhoan
We report the results of a calculation of the K → pipi matrix elements of the DeltaI = 3/2 operators. Relying on the 3-flavor effective Hamiltonian, we calculate the low energy contribution to the matrix elements in quenched lattice QCD with the DBW2 action using domain wall fermions, while the high energy contribution is included in the Wilson coefficients. In order to generate interacting pipi states with non-zero relative momentum in lattice, we apply anti-periodic boundary conditions on pions. Since only the magnitude of the overlap of our interpolating operators with the initial and final state is determined, we can calculate only the magnitude of the matrix elements. From the comparison with the experimental result, however, we find some degree of discrepancy. This discrepancy might be ascribed to the unphysical kinematics we choose in this report.
Valence-quark distribution functions in the kaon and pion
Chen, Chen; Chang, Lei; Roberts, Craig D.; Wan, Shaolong; Zong, Hong-Shi
2016-04-01
We describe expressions for pion and kaon dressed-quark distribution functions that incorporate contributions from gluons which bind quarks into these mesons and hence overcome a flaw of the commonly used handbag approximation. The distributions therewith obtained are purely valence in character, ensuring that dressed quarks carry all the meson's momentum at a characteristic hadronic scale and vanish as (1 -x )2 when Bjorken-x →1 . Comparing such distributions within the pion and kaon, it is apparent that the size of S U (3 ) -flavor symmetry breaking in meson parton distribution functions is modulated by the flavor dependence of dynamical chiral symmetry breaking. Corrections to these leading-order formulas may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea quarks. Working with available empirical information, we build an algebraic framework that is capable of expressing the principal impact of both classes of corrections. This enables a realistic comparison with experiment which allows us to identify and highlight basic features of measurable pion and kaon valence-quark distributions. We find that whereas roughly two thirds of the pion's light-front momentum is carried by valence dressed quarks at a characteristic hadronic scale; this fraction rises to 95% in the kaon; evolving distributions with these features to a scale typical of available Drell-Yan data produces a kaon-to-pion ratio of u -quark distributions that is in agreement with the single existing data set, and predicts a u -quark distribution within the pion that agrees with a modern reappraisal of π N Drell-Yan data. Precise new data are essential in order to validate this reappraisal and because a single modest-quality measurement of the kaon-to-pion ratio cannot be considered definitive.
Elastic scattering of low energy pions by nuclei and the in-medium isovector pi N amplitude
Friedman, E; Breitschopf, J; Clement, H; Denz, H; Doroshkevich, E; Erhardt, A; Hofman, G J; Kritchman, S; Meier, R; Wagner, G J; Yaari, G
2005-01-01
Measurements of elastic scattering of 21.5 MeV pi+ and pi- by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer. Absolute calibration was made by parallel measurements of Coulomb scattering of muons. Parameters of a pion-nucleus optical potential were obtained from fits to all eight angular distributions put together. The `anomalous' s-wave repulsion known from pionic atoms is clearly observed and could be removed by introducing a chiral-motivated density dependence of the isovector scattering amplitude, which also greatly improved the fits to the data. The empirical energy dependence of the isoscalar amplitude also improves the fits to the data but, contrary to what is found with pionic atoms, on its own is incapable of removing the anomaly.
Effects of $\\rho$-meson width on pion distributions in heavy-ion collisions
Huovinen, Pasi; Marczenko, Michał; Morita, Kenji; Redlich, Krzysztof; Sasaki, Chihiro
2016-01-01
The influence of the finite width of $\\rho$ meson on the pion momentum distribution is studied quantitatively in the framework of the S-matrix approach combined with a blast-wave model to describe particle emissions from an expanding fireball. We find that the proper treatment of resonances which accounts for their production dynamics encoded in data for partial wave scattering amplitudes can substantially modify spectra of daughter particles originating in their two body decays. In particular, it results in an enhancement of the low-$p_T$ pions from the decays of $\\rho$ mesons which improves the quantitative description of the pion spectra in heavy ion collisions obtained by the ALICE collaboration at the LHC energy.
Parton distributions for the pion in a chiral quark model
Ruiz-Arriola, E
2001-01-01
Parton distributions for the pion are studied in a chiral quark model characterized by a quark propagator for which a spectral representation is assumed. Electromagnetic and chiral symmetry constraints are imposed through the relevant Ward-Takahashi identities for flavoured vertex functions. Finiteness of the theory, requires the spectral function to be non-positive definite. Straightforward calculation yields the result that the pion structure function becomes one in the chiral limit, regardless of the details of the spectral function. LO and NLO evolution provide a satisfactory description of phenomenological parameterizations of the valence distribution functions but fails to describe gluon and sea distributions.
Valence-quark distribution functions in the kaon and pion
Energy Technology Data Exchange (ETDEWEB)
Chen, Chen; Chang, Lei; Roberts, Craig D.; Wan, Shaolong; Zong, Hong-Shi
2016-04-18
We describe expressions for pion and kaon dressed-quark distribution functions that incorporate contributions from gluons which bind quarks into these mesons and hence overcome a flaw of the commonly used handbag approximation. The distributions therewith obtained are purely valence in character, ensuring that dressed quarks carry all the meson’s momentum at a characteristic hadronic scale and vanish as ( 1 - x ) ^{2} when Bjorken- x → 1 . Comparing such distributions within the pion and kaon, it is apparent that the size of S U ( 3 ) -flavor symmetry breaking in meson parton distribution functions is modulated by the flavor dependence of dynamical chiral symmetry breaking. Corrections to these leading-order formulas may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea quarks. Working with available empirical information, we build an algebraic framework that is capable of expressing the principal impact of both classes of corrections. This enables a realistic comparison with experiment which allows us to identify and highlight basic features of measurable pion and kaon valence-quark distributions. We find that whereas roughly two thirds of the pion’s light-front momentum is carried by valence dressed quarks at a characteristic hadronic scale; this fraction rises to 95% in the kaon; evolving distributions with these features to a scale typical of available Drell-Yan data produces a kaon-to-pion ratio of u -quark distributions that is in agreement with the single existing data set, and predicts a u -quark distribution within the pion that agrees with a modern reappraisal of π N Drell-Yan data. Precise new data are essential in order to validate this reappraisal and because a single modest-quality measurement of the kaon-to-pion ratio cannot be considered definitive.
In-Medium Pion Valence Distributions in a Light-Front Model
de Melo, J P B C; Ahmed, I
2016-01-01
Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.
Basic features of the pion valence-quark distribution function
Directory of Open Access Journals (Sweden)
Lei Chang
2014-10-01
Full Text Available The impulse-approximation expression used hitherto to define the pion's valence-quark distribution function is flawed because it omits contributions from the gluons which bind quarks into the pion. A corrected leading-order expression produces the model-independent result that quarks dressed via the rainbow–ladder truncation, or any practical analogue, carry all the pion's light-front momentum at a characteristic hadronic scale. Corrections to the leading contribution may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we use an algebraic model to express the principal impact of both classes of corrections. This enables a realistic comparison with experiment that allows us to highlight the basic features of the pion's measurable valence-quark distribution, qπ(x; namely, at a characteristic hadronic scale, qπ(x∼(1−x2 for x≳0.85; and the valence-quarks carry approximately two-thirds of the pion's light-front momentum.
Beam-Spin Asymmetries in the Azimuthal Distribution of Pion Electroproduction
Airapetian, A; Amarian, M; Andrus, A; Aschenauer, E C; Augustyniak, W; Avakian, H; Avakian, R; Avetisian, A; Avetisyan, E; Bacchetta, A; Bailey, P; Belostotskii, S; Bianchi, N; Blok, H P; Böttcher, H; Borisov, A; Borysenko, A; Brüll, A; Bryzgalov, V; Capiluppi, M; Capitani, G P; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; Deconinck, W; De Leo, R; Demey, M; De Nardo, L; De Sanctis, E; Devitsin, E; Diefenthaler, M; Di Nezza, P; Dreschler, J; Düren, M; Ehrenfried, M; Elalaoui-Moulay, A; Elbakian, G; Ellinghaus, F; Elschenbroich, U; Fabbri, R; Fantoni, A; Felawka, L; Frullani, S; Funel, A; Gapienko, G; Gapienko, V; Garibaldi, F; Garrow, K; Gavrilov, G; Karibian, V; Giordano, F; Grebenyuk, O; Gregor, I M; Guler, H; Hadjidakis, C; Hafidi, K; Hartig, M; Hasch, D; Hasegawa, T; Hesselink, W H A; Hillenbrand, A; Hoek, M; Holler, Y; Hommez, B; Hristova, I; Iarygin, G; Ivanilov, A; Izotov, A; Jackson, H E; Jgoun, A; Kaiser, R; Keri, T; Kinney, E; Kiselev, A; Kobayashi, T; Kopytin, M; Korotkov, V; Kozlov, V; Krauss, B; Kravchenko, P; Krivokhizhin, V G; Lagamba, L; Lapikas, L; Lenisa, P; Liebing, P; Linden-Levy, L A; Lorenzon, W; Lü, J; Lu, S; Ma, B Q; Maiheu, B; Makins, N C R; Mao, Y; Marianski, B; Marukyan, H; Masoli, F; Mexner, V; Meyners, N; Michler, T; Miklukho, O; Miller, C A; Miyachi, Y; Muccifora, V; Murray, M; Nagaitsev, A; Nappi, E; Naryshkin, Yu; Negodaev, M; Nowak, W D; Oganessyan, K; Ohsuga, H; Osborne, A; Perez-Benito, R; Pickert, N; Raithel, M; Reggiani, D; Reimer, P E; Reischl, A; Reolon, A R; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubacek, L; Rubin, J; Ryckbosch, D; Salomatin, Y; Sanjiev, I; Savin, I; Schäfer, A; Schnell, G; Schüler, K P; Seele, J; Seidl, R; Seitz, B; Shearer, C; Shibata, T A; Shutov, V; Sinram, K; Stancari, M; Statera, M; Steffens, E; Steijger, J J M; Stenzel, H; Stewart, J; Stinzing, F; Streit, J; Tait, P; Tanaka, H; Taroian, S P; Tchuiko, B; Terkulov, A R; Trzcinski, A; Tytgat, M; Vandenbroucke, A; Van der Nat, P B; van der Steenhoven, G; Van Haarlem, Y; Vikhrov, V; Vogel, C; Wang, S; Ye, Y; Ye, Z; Yen, S; Zihlmann, B; Zupranski, P
2007-01-01
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the {HERMES} spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle $\\phi$ of the hadron production plane around the virtual photon direction relative to the lepton scattering plane was measured for $\\pi^+,\\pi^-$ and $\\pi^0$ mesons. The dependence of this amplitude on the Bjorken scaling variable and on the pion fractional energy and transverse momentum is presented. The results are compared to theoretical model calculations.
Lattice Results for Low Moments of Light Meson Distribution Amplitudes
Arthur, R; Brommel, D; Donnellan, M A; Flynn, J M; Juttner, A; Rae, T D; Sachrajda, C T.C
2011-01-01
As part of the UKQCD and RBC collaborations' N_f=2+1 domain-wall fermion phenomenology programme, we calculate the first two moments of the light-cone distribution amplitudes of the pseudoscalar mesons pion and kaon and the (longitudinally-polarised) vector mesons rho, K-star and phi. We obtain the desired quantities with good precision and are able to discern the expected quark-mass dependence of SU(3)-flavour breaking effects. An important ingredient of the calculation is the nonperturbative renormalisation of lattice operators using the RI'/MOM technique.
Valence-quark distribution functions in the kaon and pion
Chen, Chen; Roberts, Craig D; Wan, Shaolong; Zong, Hong-Shi
2016-01-01
We describe expressions for pion and kaon dressed-quark distribution functions that incorporate contributions from gluons which bind quarks into these mesons and hence overcome a flaw of the commonly used handbag approximation. The distributions therewith obtained are purely valence in character, ensuring that dressed-quarks carry all a meson's momentum at a characteristic hadronic scale and vanishing as $(1-x)^2$ when Bjorken-$x\\to 1$. Comparing such distributions within the pion and kaon, it is apparent that the size of SU(3)-flavour symmetry breaking in meson parton distribution functions is modulated by the flavour dependence of dynamical chiral symmetry breaking. Corrections to these leading-order formulae may be divided into two classes, responsible for shifting dressed-quark momentum into glue and sea-quarks. Working with available empirical information, we build an algebraic framework that is capable of expressing the principal impact of both classes of corrections. This enables a realistic comparison...
Pion-nucleon amplitude near threshold the sigma-term and scattering lengths beyond few loops
Kondratyuk, S
2002-01-01
The pion-nucleon amplitude is considered in the vicinity of the elastic scattering threshold within a relativistic dynamical model dressing the $\\pi N N$ and $\\pi N \\Delta$ vertices self-consistently with an infinite number of meson loops. The dressing is formulated as solution of a system of coupled integral equations incorporating unitarity, crossing symmetry and analyticity constraints. The calculated scattering lengths and the sigma-term agree with recent data analyses. In this model multiple loops are significant both below and at threshold. The contribution of the $\\Delta$ resonance is discussed, including effects of its dressing. A comparison with the approaches of chiral perturbation theory and the Bethe-Salpeter equation is outlined.
Mass extrapolation of the amplitude for pion production in N-N collision
Energy Technology Data Exchange (ETDEWEB)
Afnan, I.R.; Thomas, A.W.
1977-06-01
The S-wave pion production process (at q/sub ..pi../ = 0) is calculated as a function of the mass of the produced pion. The invariant matrix element is found to be surprisingly constant over a large range of pion mass.
First Amplitude Analysis of Resonant Structures in the 5-Pion Continuum at COMPASS
Neubert, Sebastian
The study of hadronic scattering amplitudes and in particular the spectroscopy of light mesons provide a unique tool to investigate the strong interaction. At very low energies the meson spec- trum is governed by the spontaneous breakdown of the chiral symmetry of the QCD vacuum. At higher masses a series of resonances appears. Their origin and their relation to chiral symmetry breaking is only partly understood. In particular for masses above 1.6 GeV = c 2 while a large number of states have been reported they are still poorly known experimentally. One compli- cation are multi-body final states into which heavy mesons can decay. In this thesis a method for the amplitude analysis of the + + system is being developed. The COMPASS ex- periment at CERN uses the diffractive dissociation of a 190 GeV pion beam as a source of meson resonances up to masses of about 3 GeV = c 2 . A partial wave decomposition of the 5 system is presented here which for the first time allows to search for mesonic 5-body resonances. A n...
Parton Distributions of Pions in the Valon Model
Institute of Scientific and Technical Information of China (English)
杨纯斌
2003-01-01
Based on the universality of the parton distributions inside valons, parton distributions of pions are investigated and parametrized from the experimentally given parton distributions of proton within the valon model The structure function F2(x) is given at fixed scale Q20 = 1 GeV2. Due to the abundance of the pair numbers of sea quarks at a very small x region, the structure function decreases rapidly for small x to a local minimum. Then from the contribution of the valence quarks, F2(x) increases to a local maximum at x (∽－)0.5.
On the Distribution of Neutral and Charged Pions through the Production of a Classical Pion Field
Anselm, A A; Bander, Myron
1994-01-01
High energy reactions may produce a state around the collision point that is best described by a classical pion field. Such a field might be an isospin rotated vacuum of the chiral $\\sigma$-model or, as discussed in this work, a solution of the equations of motion resultinng from the coupling of fields of this model to quarks produced in the collision. In such configurations all directions in isospin space are allowed leading to a sizable probability of events with, essentially, only charged particles (Centauros) or all neutral particles (anti-Centauros). (In more common statistical models of multiparticle production, the probability of such events is suppressed exponentially by the total multiplicity.) We find that the isospin violation due to the mass difference of the up and down quarks has a significant effect on these distributions and enhances the production of events consisting predominantly of neutral particles.
Towards a model of pion generalized parton distributions from Dyson-Schwinger equations
Energy Technology Data Exchange (ETDEWEB)
Moutarde, H. [CEA, Centre de Saclay, IRFU/Service de Physique Nucléaire, F-91191 Gif-sur-Yvette (France)
2015-04-10
We compute the pion quark Generalized Parton Distribution H{sup q} and Double Distributions F{sup q} and G{sup q} in a coupled Bethe-Salpeter and Dyson-Schwinger approach. We use simple algebraic expressions inspired by the numerical resolution of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly check the support and polynomiality properties, and the behavior under charge conjugation or time invariance of our model. We derive analytic expressions for the pion Double Distributions and Generalized Parton Distribution at vanishing pion momentum transfer at a low scale. Our model compares very well to experimental pion form factor or parton distribution function data.
Martín, R García-; Peláez, J R; de Elvira, J Ruiz; Ynduráin, F J
2011-01-01
We improve our description of pion-pion scattering data by imposing additional requirements to our previous fits, in the form of once-subtracted Roy-like equations, while extending our analysis up to 1100 MeV. We provide simple and ready to use parametrizations of the amplitude. In addition, we present a detailed description and derivation of these once-subtracted dispersion relations that, in the 450 to 1100 MeV region, provide an additional constraint which is much stronger than our previous requirements of Forward Dispersion Relations and standard Roy equations. The ensuing constrained amplitudes describe the existing data with rather small uncertainties in the whole region from threshold up to 1100 MeV, while satisfying very stringent dispersive constraints. For the S0 wave, this requires an improved matching of the low and high energy parametrizations. Also for this wave we have considered the latest low energy Kl4 decay results, including their isospin violation correction, and we have removed some cont...
First amplitude analysis of resonant structures in the 5-pion continuum at COMPASS
Energy Technology Data Exchange (ETDEWEB)
Neubert, Sebastian
2012-07-06
The study of hadronic scattering amplitudes and in particular the spectroscopy of light mesons provide a unique tool to investigate the strong interaction. At very lowenergies the meson spectrum is governed by the spontaneous breakdown of the chiral symmetry of the QCD vacuum. At higher masses a series of resonances appears. Their origin and their relation to chiral symmetry breaking is only partly understood. In particular for masses above {proportional_to} 1.6 GeV/c{sup 2} while a large number of states have been reported they are still poorly known experimentally. One complication are multi-body final states into which heavy mesons can decay. In this thesis a method for the amplitude analysis of the {pi}{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} system is being developed. The COMPASS experiment at CERN uses the diffractive dissociation of a 190 GeV pion beam as a source of meson resonances up to masses of about 3 GeV/c{sup 2}. A partial wave decomposition of the 5{pi} system is presented here which for the first time allows to search for mesonic 5-body resonances. A novel technique based on an evolutionary algorithm is developed to solve the problem of finding a reliable truncation of the partial wave expansion of the hadronic amplitude. The method for the first time allows the investigation of systematic uncertainties introduced by the use truncated isobar model amplitudes. The well known {pi}{sub 2}(1670) and {pi}(1800) states are found with good agreement to measurements in other channels. In addition there is evidence for several other resonant contributions, among them the controversial {pi}{sub 2}(1880) which is being discussed as a hybrid-meson candidate. In the course of the analysis a new software-framework for amplitude analysis has been developed, which is now being used by the COMPASS collaboration for the analysis of several hadronic channels. Future experiments in particle physics will have to collect large amounts of data in order to
The in-medium isovector pi N amplitude from low energy pion scattering
Friedman, E; Breitschopf, J; Clement, H; Denz, H; Doroshkevich, E; Erhardt, A; Hofman, G J; Meier, R; Wagner, G J; Yaari, G
2004-01-01
Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni and Zr have been measured as part of a study of the pion-nucleus potential across threshold. The `anomalous' repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.
In-medium isovector piN amplitude from low-energy pion scattering.
Friedman, E; Bauer, M; Breitschopf, J; Clement, H; Denz, H; Doroshkevich, E; Erhardt, A; Hofman, G J; Meier, R; Wagner, G J; Yaari, G
2004-09-17
Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni, and Zr have been measured as part of a study of the pion-nucleus potential across the threshold. The "anomalous" repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.
The in-medium isovector pi N amplitude from low energy pion scattering
Friedman, E; Bauer, M.; Breitschopf, J.; H. Clement; Denz, H; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Meier, R.; Wagner, G. J.; Yaari, G
2004-01-01
Differential cross sections for elastic scattering of 21.5 MeV positive and negative pions by Si, Ca, Ni and Zr have been measured as part of a study of the pion-nucleus potential across threshold. The `anomalous' repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an e...
In-Medium Isovector πN Amplitude from Low-Energy Pion Scattering
Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Meier, R.; Wagner, G. J.; Yaari, G.
2004-09-01
Differential cross sections for elastic scattering of 21.5MeV positive and negative pions by Si, Ca, Ni, and Zr have been measured as part of a study of the pion-nucleus potential across the threshold. The “anomalous” repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.
Nucleon distribution amplitudes from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Kaltenbrunner, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (DE). John von Neumann-Inst. fuer Computing NIC] (and others)
2008-04-15
We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature. (orig.)
Particle Distribution Modification by Low Amplitude Modes
Energy Technology Data Exchange (ETDEWEB)
White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.
2009-08-28
Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.
Finite-Volume Partially-Quenched Two-Pion Amplitudes in the I=0 Channel
Lin, C J D; Pallante, E; Sachrajda, Christopher T C; Villadoro, Giovanni
2004-01-01
We present a study of the finite-volume two-pion matrix elements and correlation functions of the I=0 scalar operator, in full and partially quenched QCD, at one-loop order in chiral perturbation theory. In partially quenched QCD, when the sea and valence light quark masses are not equal, the lack of unitarity leads to the same inconsistencies as in quenched QCD and the matrix elements cannot be determined. It is possible, however, to overcome this problem by requiring the masses of the valence and sea quarks to be equal for the u and d quarks while keeping the strange quark (s) quenched (or partially quenched), but only in the kinematic region where the two-pion energy is below the two-kaon threshold. Although our results are obtained at NLO in chiral perturbation theory, they are more general and are also valid for non-leptonic kaon decays (we also study the matrix elements of (8,1) operators, such as the QCD penguin operator Q6). We point out that even in full QCD, where any problems caused by the lack of ...
Quasi Distribution Amplitude of Heavy Quarkonia
Jia, Yu
2015-01-01
The recently-proposed quasi distributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions (PDF) and distribution amplitudes (DA), directly in the $x$-space. Owing to its excessive simplicity, the heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DA. In the framework of non-relativistic QCD (NRQCD) factorization, we compute the order-$\\alpha_s$ correction to both light-cone distribution amplitudes (LCDA) and quasi-DA associated with the lowest-lying quarkonia, with the transverse momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2-3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the fut...
Lattice study of the Boer-Mulders transverse momentum distribution in the pion
Energy Technology Data Exchange (ETDEWEB)
Engelhardt, Michael; Musch, Bernhard; Haegler, Philipp; Negele, John; Schaefer, Andreas
2014-11-01
The Boer-Mulders transverse momentum-dependent parton distribution (TMD) characterizes polarized quark transverse momentum in an unpolarized hadron. Techniques previously developed for lattice calculations of nucleon TMDs are applied to the pion. These techniques are based on the evaluation of matrix elements of quark bilocal operators containing a staple-shaped Wilson connection. Results for the Boer-Mulders transverse momentum shift in the pion, obtained at a pion mass of mπ=518MeV, are presented and compared to corresponding results in the nucleon.
Elastic scattering of low energy pions by nuclei and the in-medium isovector pi N amplitude
Friedman, E; Bauer, M.; Breitschopf, J.; H. Clement; Denz, H; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Kritchman, S.; Meier, R.; Wagner, G. J.; Yaari, G
2005-01-01
Measurements of elastic scattering of 21.5 MeV pi+ and pi- by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer. Absolute calibration was made by parallel measurements of Coulomb scattering of muons. Parameters of a pion-nucleus optical potential were obtained from fits to all eight angular distributions put together. The `anomalous' s-wave repulsion known from pionic atoms is clearly observed and could be removed by introducing a chiral-motivated density dependence of the ...
Transition Distribution Amplitudes for gamma* gamma collisions
Lansberg, J P; Szymanowski, L
2008-01-01
We study the exclusive production of pi-pi and rho-pi in hard gamma* gamma scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of Transition Distribution Amplitudes (TDA) is used to perform a QCD calculation of these reactions thanks to two simple models for TDAs. The sizable cross sections for rho-pi and pi-pi production may be tested at intense electron-positron colliders such as CLEO and B factories (Belle and BaBar).
Impact Representation of Generalized Distribution Amplitudes
Pire, B
2003-01-01
We develop an impact representation for the generalized distribution amplitude which describes the exclusive hadronization of a quark-antiquark pair to a pair of mesons. Experiments such as gamma^* gamma -> pi pi and gamma^* N -> pi pi N' are shown to probe the transverse size of the hadronization region of the quark antiquark pair that one can interpret as the transverse overlap of the two emerging mesons. An astonishing feature of this description is that low energy pi pi phase shift analysis can be used for understanding some properties of quark hadronization process.
\\pi N transition distribution amplitudes: their symmetries and constraints from chiral dynamics
Pire, Bernard; Szymanowski, Lech
2011-01-01
Baryon to meson Transition Distribution Amplitudes (TDAs) extend the concept of generalized parton distributions. Baryon to meson TDAs appear as building blocks in the colinear factorized description of amplitudes for a class of hard exclusive reactions, prominent examples of which being hard exclusive meson electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a meson and a lepton pair. We study general properties of these objects following from the underlying symmetries of QCD. In particular, the Lorentz symmetry results in the polynomiality property of the Mellin moments in longitudinal momentum fractions. We present a detailed account of isotopic and permutation symmetry properties of nucleon to pion (\\pi N) TDAs. This restricts the number of independent leading twist \\pi N TDAs to eight functions providing description of all isotopic channels. Using chiral symmetry and the crossing relation between \\pi N TDAs and \\pi N generalized distribution amplitudes we establ...
Feasibility study for the measurement of πN transition distribution amplitudes with PANDA
Atomssa, Ermias
2016-05-01
Transition Distribution Amplitudes (TDA) are parametrizations of the hadronic matrix elements that occur in the perturbative Quantum Chromo Dynamics (QCD) calculations of a certain family of reactions within the framework of collinear factorization. We propose a complete feasibility study of the measurement of one of the reactions covered by the TDA models p ¯p →π0J /ψ (J /ψ →e+e-) at PANDA (AntiProton ANnihilation at DArmstadt) experiment currently under construction at the future FAIR (Facility for Antiproton and Ion Research). We show that PANDA will be ideally suited to access the relevant observables, in particular the pion-to-nucleon TDAs (πN TDAs) which are important for the understanding of the pion cloud contribution in the nucleon wave function.
Flavour symmetry breaking in the kaon parton distribution amplitude
Directory of Open Access Journals (Sweden)
Chao Shi
2014-11-01
Full Text Available We compute the kaon's valence-quark (twist-two parton distribution amplitude (PDA by projecting its Poincaré-covariant Bethe–Salpeter wave-function onto the light-front. At a scale ζ=2 GeV, the PDA is a broad, concave and asymmetric function, whose peak is shifted 12–16% away from its position in QCD's conformal limit. These features are a clear expression of SU(3-flavour-symmetry breaking. They show that the heavier quark in the kaon carries more of the bound-state's momentum than the lighter quark and also that emergent phenomena in QCD modulate the magnitude of flavour-symmetry breaking: it is markedly smaller than one might expect based on the difference between light-quark current masses. Our results add to a body of evidence which indicates that at any energy scale accessible with existing or foreseeable facilities, a reliable guide to the interpretation of experiment requires the use of such nonperturbatively broadened PDAs in leading-order, leading-twist formulae for hard exclusive processes instead of the asymptotic PDA associated with QCD's conformal limit. We illustrate this via the ratio of kaon and pion electromagnetic form factors: using our nonperturbative PDAs in the appropriate formulae, FK/Fπ=1.23 at spacelike-Q2=17 GeV2, which compares satisfactorily with the value of 0.92(5 inferred in e+e− annihilation at s=17 GeV2.
A perspective on Dyson-Schwinger equation: toy model of Pion
Directory of Open Access Journals (Sweden)
Chang Lei
2016-01-01
Full Text Available We suggest a model representation of pion leading Bethe-Salpeter amplitude which involves a particular momentum dependence. Combining the constituent-quark propagator approximation we discuss the twist-2 parton distribution amplitude, parton distribution function, pion elastic form factor and π − γ transition form factor.
Experimental access to transition distribution amplitudes with the PANDA experiment at FAIR
Energy Technology Data Exchange (ETDEWEB)
Zambrana, Manuel; Ahmed, Samer; Deiseroth, Malte; Froehlich, Bertold; Khaneft, Dmitry; Lin, Dexu; Noll, Oliver; Valente, Roserio; Zimmermann, Iris [Institut fuer Kernphysik, Johannes Gutenberg Universitaet, Mainz (Germany); Helmholtz-Institut Mainz (Germany); Mora Espi, Maria Carmen; Ahmadi, Heybat; Capozza, Luigi; Dbeyssi, Alaa; Morales, Cristina; Rodriguez Pineiro, David [Helmholtz-Institut Mainz (Germany); Maas, Frank [Institut fuer Kernphysik, Johannes Gutenberg Universitaet, Mainz (Germany); Helmholtz-Institut Mainz (Germany); Prisma Cluster of Excellence, Mainz (Germany)
2015-07-01
We address the feasibility of accessing proton to pion Transition Distribution Amplitudes with the future PANDA detector at the FAIR facility. At high center of mass energy and four-momentum transfer, the amplitude of signal channel anti pp → e{sup +}e{sup -}π{sup 0} admits a QCD factorized description in terms of Distribution Amplitudes and Transition Distribution Amplitudes in the forward and backward regions. Assuming a factorized cross section, feasibility studies of measuring anti pp → e{sup +}e{sup -}π{sup 0} with PANDA have been performed at the center of mass energy squared s=5 GeV{sup 2} and s=10 GeV{sup 2}, in the kinematic region of four-momentum transfer 3.0 < q{sup 2} < 4.3 GeV{sup 2} and 5 < q{sup 2} < 9 GeV{sup 2}, respectively, with a neutral pion scattered in the forward or backward cone cosθ{sub π{sup 0}} > 0.5 in the anti pp center of mass frame. These include detailed simulations on signal reconstruction efficiency, rejection of the most severe background channel, i.e. anti pp → π{sup +}π{sup -}π{sup 0}, and the feasibility of the measurement using a sample of 2 fb{sup -1} of integrated luminosity. Results of the simulations show that a background rejection factor from 10{sup 7} at s=5 GeV{sup 2} to 10{sup 8} at s=10 GeV{sup 2} can be achieved, while keeping the signal reconstruction efficiency at the level of 40%, and that a clean lepton signal can be reconstructed with 2 fb{sup -1} of integrated luminosity at both energies. The ''measured'' cross sections with the simulations are used to test QCD factorization at the leading order by measuring scaling laws and fitting angular distributions.
INVESTIGATION OF POLAR AND AZIMUTHAL DISTRIBUTIONS OF SUBTHRESHOLD PIONS AT INTERMEDIATE ENERGIES
SCHUBERT, A; HOLZMANN, R; HLAVAC, S; KULESSA, R; NIEBUR, W; SIMON, RS; LAUTRIDOU, P; LEFEVRE, F; MARQUES, M; MATULEWICZ, T; MITTIG, W; OSTENDORF, RW; ROUSSELCHOMAZ, P; SCHUTZ, Y; LOHNER, H; VANPOL, JHG; SIEMSSEN, RH; WILSCHUT, HW; BALLESTER, F; DIAZ, J; MARIN, A; MARTINEZ, G; METAG, [No Value; NOVOTNY, R; WAGNER, [No Value; QUEBERT, J
1994-01-01
We present data on pi0 emission coincident with projectile-like fragments from Ar-36 + Au-197 and Ar-36 + C-12 reactions at 95 MeV/u. The pion polar and azimuthal distributions, obtained for different impact parameters, are interpreted in terms of strong final-state interactions. We propose to explo
The Centauro events as a result of induced pions emission
Karmanov, V A
2002-01-01
It is shown that only in the case of n pion production amplitude (at n > 10), which is symmetric enough relative to the momenta permutations, there is appreciable probability of events with nothing but charged or nothing but neutral pions. Significant enhancement of the probability of these events in comparison with that follows from Poisson distribution is caused by induced pions emission, in complete analogy with the phenomenon of the induced photon emission in QED.
Mass of nonrelativistic meson from leading twist distribution amplitudes
Energy Technology Data Exchange (ETDEWEB)
Braguta, V. V., E-mail: braguta@mail.ru [Institute for High Energy Physics (Russian Federation)
2011-01-15
In this paper distribution amplitudes of pseudoscalar and vector nonrelativistic mesons are considered. Using equations of motion for the distribution amplitudes, relations are derived which allow one to calculate the masses of nonrelativistic pseudoscalar and vector meson if the leading twist distribution amplitudes are known. These relations can be also rewritten as relations between the masses of nonrelativistic mesons and infinite series of QCD operators, what can be considered as an exact version of Gremm-Kapustin relation in NRQCD.
QCD factorization for the pion diffractive dissociation to two jets
Braun, V M; Schäfer, A; Szymanowski, L
2001-01-01
We calculate the cross section of a pion diffraction dissociation in two jets with large transverse momenta originating from a hard gluon exchange between the pion constituents. To the leading logarithmic accuracy (in energy), the contribution coming from small transverse separations between the quark and the antiquark in the pion acquires the expected factorized form, the longitudinal momentum distribution of the jets being proportional to the pion distribution amplitude. The hard gluon exchange can in this case be considered as a part of the unintegrated gluon distribution. Beyond the leading logarithms (in energy) this proportionality does not hold. Moreover, the collinear factorization appears to be broken by the end-point singularities. Remarkably enough, the longitudinal momentum distribution of the jets for the non-factorizable contribution is calculable, and turns out to be the same as for the factorizable contribution with the asymptotic pion distribution amplitude.
Hadron tomography studies by generalized parton distributions and distribution amplitudes
Kumano, S
2016-01-01
We discuss hadron-tomography studies for the nucleon and exotic hadrons by high-energy hadron reactions. First, the constituent-counting rule is explained for determining internal quark configurations of exotic-hadron candidates by scaling properties of high-energy exclusive cross sections. Next, possibilities are discussed for investigating the generalized parton distributions (GPDs) of the nucleon and exotic hadrons at J-PARC. In particular, we study hadronic $2 \\to 3$ process $p+p \\to N+\\pi+B$, exclusive Drell-Yan process, and exotic-hadron GPDs. For determining three-dimensional structure of unstable exotic hadrons, we consider $s$-$t$ crossed quantities of the GPDs called generalized distribution amplitudes (GDAs), which can be investigated at KEKB. We explain possible studies of the GDAs by two-photon processes.
Coulomb dissociation of a fast pion into two jets
Ivanov, D Yu
2001-01-01
We calculate the electromagnetic contribution to the scattering amplitude of pion diffractive dissociation into di-jets which is described by one photon exchange. The result shows that the factorization procedure known for the description of exclusive reactions holds also for this quasi-exclusive process. We find that the longitudinal momentum distribution of di-jets does not depend on the form of the pion distribution amplitude. We discuss the magnitude of the cross section.
Baryon octet distribution amplitudes in Wandzura-Wilczek approximation
Energy Technology Data Exchange (ETDEWEB)
Anikin, I.V. [Joint Institute of Nuclear Research, Moscow (Russian Federation). Bogoliubov Lab. of Theoretical Physics; Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Manashov, A.N. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2015-12-15
We study higher twist distribution amplitudes for the SU{sub F}(3) baryon octet. We identify independent functions for all baryons in the isospin symmetry limit and calculate the Wandzura-Wilczek contributions to the twist-4 and 5 distributions amplitudes.
Huang, Z; Huang, Zheng; Suzuki, Mahiko
1996-01-01
We obtain the general analytic solutions of the nonlinear \\sigma-model in 3+1 dimensions as the candidates for the disoriented chiral condensate (DCC). The nonuniformly isospin-orientated solutions are shown to be related to the uniformly oriented ones through the chiral (axial) rotations. We discuss the pion charge distribution arising from these solutions. The distribution dP/df=1/(2\\sqrt{f}) holds for the uniform solutions in general and the nonuniform solutions in the 1+1 boost invariant case. For the nonuniform solution in 1+1 without a boost-invariance and in higher dimensions, the distribution does not hold in the integrated form. However, it is applicable to the pions selected from a small segment in the momentum phase space. We suggest that the nonuniform DCC's may correspond to the mini-Centauro events.
Higher Twist Distribution Amplitudes of the Nucleon in QCD
Braun, V M; Mahnke, N; Stein, E
2000-01-01
We present the first systematic study of higher-twist light-cone distribution amplitudes of the nucleon in QCD. We find that the valence three-quark state is described at small transverse separations by eight independent distribution amplitudes. One of them is leading twist-3, three distributions are twist-4 and twist-5, respectively, and one is twist-6. A complete set of distribution amplitudes is constructed, which satisfies equations of motion and constraints that follow from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules.
Meson cloud effects on the pion quark distribution function in the chiral constituent quark model
Watanabe, Akira; Suzuki, Katsuhiko
2016-01-01
We investigate the valence quark distribution function of the pion $v^{\\pi}(x,Q^2)$ in the framework of the chiral constituent quark model and evaluate the meson cloud effects on $v^{\\pi}(x,Q^2)$. We explicitly demonstrate how the meson cloud effects affect $v^{\\pi}(x,Q^2)$ in detail. We find that the meson cloud correction causes an overall 32\\% reduction of the valence quark distribution and an enhancement at the small Bjorken $x$ regime. Besides, we also find that the dressing effect of the meson cloud will make the valence quark distribution to be softer in the large $x$ region.
Concurrent approaches to Generalized Parton Distribution modeling: the pion's case
Chouika, N.; Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.
2017-03-01
The concept of Generalized Parton Distributions promises an understanding of the generation of the charge, spin, and energy-momentum structure of hadrons by quarks and gluons. Forthcoming measurements with unprecedented accuracy at Jefferson Lab and at CERN will challenge our quantitative description of the three-dimensional structure of hadrons. To fully exploit these future measurements, new tools and models are currently being developed. We explain the difficulties of Generalized Parton Distribution modeling, and present some recent progresses. In particular we describe the symmetry-preserving Dyson-Schwinger and Bethe-Salpeter framework. We also discuss various equivalent parameterizations and sketch how to combine them to obtain models satisfying a priori all required theoretical constraints. At last we explain why these developments naturally fit in a versatile software framework, named PARTONS, dedicated to the theory and phenomenology of GPDs.
Experimental access to Transition Distribution Amplitudes with the \\={P}ANDA experiment at FAIR
Singh, B P; Keshelashvili, I; Krusche, B; Steinacher, M; Liu, B; Liu, H; Liu, Z; Shen, X; Wang, C; Zhao, J; Albrecht, M; Fink, M; Heinsius, F H; Held, T; Holtmann, T; Koch, H; Kopf, B; Kümmel, M; Kuhl, G; Kuhlmann, M; Leyhe, M; Mikirtychyants, M; Musiol, P; Mustafa, A; Pelizäus, M; Pychy, J; Richter, M; Schnier, C; Schröder, T; Sowa, C; Steinke, M; Triffterer, T; Wiedner, U; Beck, R; Hammann, C; Kaiser, D; Ketzer, B; Kube, M; Mahlberg, P; Rossbach, M; Schmidt, C; Schmitz, R; Thoma, U; Walther, D; Wendel, C; Wilson, A; Bianconi, A; Bragadireanu, M; Caprini, M; Pantea, D; Pietreanu, D; Vasile, M E; Patel, B; Kaplan, D; Brandys, P; Czyzewski, T; Czyzycki, W; Domagala, M; Hawryluk, M; Filo, G; Krawczyk, M; Kwiatkowski, D; Lisowski, E; Lisowski, F; Fiutowski, T; Idzik, M; Mindur, B; Przyborowski, D; Swientek, K; Czech, B; Kliczewski, S; Korcyl, K; Kozela, A; Kulessa, P; Lebiedowicz, P; Malgorzata, K; Pysz, K; Schäfer, W; Siudak, R; Szczurek, A; Biernat, J; Jowzaee, S; Kamys, B; Kistryn, S; Korcyl, G; Krzemien, W; Magiera, A; Moskal, P; Palka, M; Psyzniak, A; Rudy, Z; Salabura, P; Smyrski, J; Strzempek, P; Wrońska, A; Augustin, I; Lehmann, I; Nicmorus, D; Schepers, G; Schmitt, L; Al-Turany, M; Cahit, U; Capozza, L; Dbeyssi, A; Deppe, H; Dzhygadlo, R; Ehret, A; Flemming, H; Gerhardt, A; Götzen, K; Karabowicz, R; Kliemt, R; Kunkel, J; Kurilla, U; Lehmann, D; Lühning, J; Maas, F; Morales, C Morales; Espí, M C Mora; Nerling, F; Orth, H; Peters, K; Piñeiro, D Rodríguez; Saito, N; Saito, T; Lorente, A Sánchez; Schmidt, C J; Schwarz, C; Schwiening, J; Traxler, M; Valente, R; Voss, B; Wieczorek, P; Wilms, A; Zühlsdorf, M; Abazov, V M; Alexeev, G; Arefiev, A; Astakhov, V I; Barabanov, M Yu; Batyunya, B V; Davydov, Yu I; Dodokhov, V Kh; Efremov, A A; Fedunov, A G; Festchenko, A A; Galoyan, A S; Grigoryan, S; Karmokov, A; Koshurnikov, E K; Lobanov, V I; Lobanov, Yu Yu; Makarov, A F; Malinina, L V; Malyshev, V L; Mustafaev, G A; Olshevskiy, A; Pasyuk, M A; Perevalova, E A; Piskun, A A; Pocheptsov, T A; Pontecorvo, G; Rodionov, V K; Rogov, Yu N; Salmin, R A; Samartsev, A G; Sapozhnikov, M G; Shabratova, G S; Skachkov, N B; Skachkova, A N; Strokovsky, E A; Suleimanov, M K; Teshev, R Sh; Tokmenin, V V; Uzhinsky, V V; Vodopyanov, A S; Zaporozhets, S A; Zhuravlev, N I; Zorin, A G; Branford, D; Glazier, D; Watts, D; Woods, P; Britting, A; Eyrich, W; Lehmann, A; Uhlig, F; Dobbs, S; Seth, K; Tomaradze, A; Xiao, T; Bettoni, D; Carassiti, V; Ramusino, A Cotta; Dalpiaz, P; Drago, A; Fioravanti, E; Garzia, I; Savriè, M; Stancari, G; Akishina, V; Kisel, I; Kulakov, I; Zyzak, M; Arora, R; Bel, T; Gromliuk, A; Kalicy, G; Krebs, M; Patsyuk, M; Zuehlsdorf, M; Bianchi, N; Gianotti, P; Guaraldo, C; Lucherini, V; Pace, E; Bersani, A; Bracco, G; Macri, M; Parodi, R F; Bianco, S; Bremer, D; Brinkmann, K T; Diehl, S; Dormenev, V; Drexler, P; Düren, M; Eissner, T; Etzelmüller, E; Föhl, K; Galuska, M; Gessler, T; Gutz, E; Hayrapetyan, A; Hu, J; Kröck, B; Kühn, W; Kuske, T; Lange, S; Liang, Y; Merle, O; Metag, V; Mülhheim, D; Münchow, D; Nanova, M; Novotny, R; Pitka, A; Quagli, T; Rieke, J; Rosenbaum, C; Schnell, R; Spruck, B; Stenzel, H; Thöring, U; Ullrich, T; Wasem, T; Werner, M; Zaunick, H G; Ireland, D; Rosner, G; Seitz, B; Deepak, P N; Kulkarni, A V; Apostolou, A; Babai, M; Kavatsyuk, M; Lemmens, P; Lindemulder, M; Löhner, H; Messchendorp, J; Schakel, P; Smit, H; van der Weele, J C; Veenstra, R; Tiemens, M; Vejdani, S; Kalita, K; Mohanta, D P; Kumar, A; Roy, A; Sahoo, R; Sohlbach, H; Büscher, M; Cao, L; Cebulla, A; Deermann, D; Dosdall, R; Esch, S; Georgadze, I; Gillitzer, A; Goerres, A; Goldenbaum, F; Grunwald, D; Herten, A; Hu, Q; Kemmerling, G; Kleines, H; Kozlov, V; Lehrach, A; Leiber, S; Maier, R; Nellen, R; Ohm, H; Orfanitski, S; Prasuhn, D; Prencipe, E; Ritman, J; Schadmand, S; Schumann, J; Sefzick, T; Serdyuk, V; Sterzenbach, G; Stockmanns, T; Wintz, P; Wüstner, P; Xu, H; Li, S; Li, Z; Sun, Z; Rigato, V; Fissum, S; Hansen, K; Isaksson, L; Lundin, M; Schröder, B; Achenbach, P; Bleser, S; Cardinali, M; Corell, O; Deiseroth, M; Denig, A; Distler, M; Feldbauer, F; Fritsch, M; Jasinski, P; Hoek, M; Kangh, D; Karavdina, A; Lauth, W; Leithoff, H; Merkel, H; Michel, M; Motzko, C; Müller, U; Noll, O; Plueger, S; Pochodzalla, J; Sanchez, S; Schlimme, S; Sfienti, C; Steinen, M; Thiel, M; Weber, T; Zambrana, M; Dormenev, V I; Fedorov, A A; Korzihik, M V; Missevitch, O V; Balanutsa, P; Balanutsa, V; Chernetsky, V; Demekhin, A; Dolgolenko, A; Fedorets, P; Gerasimov, A; Goryachev, V; Varentsov, V; Boukharov, A; Malyshev, O; Marishev, I; Semenov, A; Konorov, I; Paul, S; Grieser, S; Hergemöller, A K; Khoukaz, A; Köhler, E; Täschner, A; Wessels, J; Dash, S; Jadhav, M; Kumar, S; Sarin, P; Varma, R; Chandratre, V B; Datar, V; Dutta, D; Jha, V; Kumawat, H; Mohanty, A K; Roy, B; Yan, Y; Chinorat, K; Khanchai, K; Ayut, L; Pornrad, S; Barnyakov, A Y; Blinov, A E; Blinov, V E; Bobrovnikov, V S; Kononov, S A; Kravchenko, E A; Kuyanov, I A; Onuchin, A P; Sokolov, A A; Tikhonov, Y A; Atomssa, E; Hennino, T; Imre, M; Kunne, R; Galliard, C Le; Ma, B; Marchand, D; Ong, S; Ramstein, B; Rosier, P; Tomasi-Gustafsson, E; Van de Wiele, J; Boca, G; Costanza, S; Genova, P; Lavezzi, L; Montagna, P; Rotondi, A; Abramov, V; Belikov, N; Bukreeva, S; Davidenko, A; Derevschikov, A; Goncharenko, Y; Grishin, V; Kachanov, V; Kormilitsin, V; Melnik, Y; Levin, A; Minaev, N; Mochalov, V; Morozov, D; Nogach, L; Poslavskiy, S; Ryazantsev, A; Ryzhikov, S; Semenov, P; Shein, I; Uzunian, A; Vasiliev, A; Yakutin, A; Yabsley, B; Bäck, T; Cederwall, B; Makónyi, K; Tegnér, P E; von Würtemberg, K M; Belostotski, S; Gavrilov, G; Izotov, A; Kashchuk, A; Levitskaya, O; Manaenkov, S; Miklukho, O; Naryshkin, Y; Suvorov, K; Veretennikov, D; Zhadanov, A; Rai, A K; Godre, S S; Duchat, R; Amoroso, A; Bussa, M P; Busso, L; De Mori, F; Destefanis, M; Fava, L; Ferrero, L; Greco, M; Maggiora, M; Maniscalco, G; Marcello, S; Sosio, S; Spataro, S; Zotti, L; Calvo, D; Coli, S; De Remigis, P; Filippi, A; Giraudo, G; Lusso, S; Mazza, G; Mingnore, M; Rivetti, A; Wheadon, R; Balestra, F; Iazzi, F; Introzzi, R; Lavagno, A; Younis, H; Birsa, R; Bradamante, F; Bressan, A; Martin, A; Clement, H; Gålnander, B; Balkeståhl, L Caldeira; Calén, H; Fransson, K; Johansson, T; Kupsc, A; Marciniewski, P; Pettersson, J; Schönning, K; Wolke, M; Zlomanczuk, J; Díaz, J; Ortiz, A; Vinodkumar, P C; Parmar, A; Chlopik, A; Melnychuk, D; Slowinski, B; Trzcinski, A; Wojciechowski, M; Wronka, S; Zwieglinski, B; Bühler, P; Marton, J; Suzuki, K; Widmann, E; Zmeskal, J; Fröhlich, B; Khaneft, D; Lin, D; Zimmermann, I; Semenov-Tian-Shansky, K
2014-01-01
We address the possibility of accessing nucleon-to-pion ($\\pi N$) Transition Distribution Amplitudes (TDAs) from $\\bar{p}p \\to e^+e^- \\pi^0$ reaction with the future \\={P}ANDA detector at the FAIR facility. At high center of mass energy and high invariant mass of the lepton pair $q^2$, the amplitude of the signal channel $\\bar{p}p \\to e^+e^- \\pi^0$ admits a QCD factorized description in terms of $\\pi N$ TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring $\\bar{p}p \\to e^+e^- \\pi^0$ with the \\={P}ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, {\\it i.e.} $\\bar{p}p \\to \\pi^+\\pi^- \\pi^0$ were performed for the center of mass energy squared $s = 5$ GeV$^2$ and $s = 10$ GeV$^2$, in the kinematic regions $3.0 0.5 $ in the proton-antiproton center of mass frame. Results of the simulation sho...
Maruyama, Tomoyuki; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.
2016-06-01
We study pion production by proton synchrotron radiation in the presence of a strong magnetic field when the Landau numbers of the initial and final protons are ni,f ∼104-105. We find in our relativistic field theory calculations that the pion decay width depends only on the field strength parameter which previously was only conjectured based upon semi-classical arguments. Moreover, we also find new results that the decay width satisfies a robust scaling relation, and that the polar angular distribution of emitted pion momenta is very narrow and can be easily obtained. This scaling implies that one can infer the decay width in more realistic magnetic fields of 1015 G, where ni,f ∼1012-1013, from the results for ni,f ∼104-105. The resultant pion intensity and angular distributions for realistic magnetic field strengths are presented and their physical implications discussed.
Revisiting the Twist-3 Distribution Amplitudes of K Meson Within the QCD Background Field Approach
Institute of Scientific and Technical Information of China (English)
钟涛; 吴兴刚; 韩华勇; 廖其力; 付海斌; 方祯云
2012-01-01
In the present paper, we investigate the kaon twist-3 distribution amplitudes （DAs）Cp within the QCD background field approach. The SUf （3）-breaking effects are studied in detail under a systematical way, especiaJ1y the sum rules for the moments of are obtained by keeping all the mass terms in the s-quark propagator consistently. After adding all the uncertainties in quadrature, the first two Gegenbauler moments of are a GeV. A detailed discussion on the properties tion parameters moments shows that the higher-order s-quark mass terms can indeed provide sizable contributions. Fhrthermore, based on the newly obtained moments, a model for the kaon twist-3 wavefunction with a better end-point behavior is constructed, which shall be useful for perturbative QCD calculations. As a byproduct, we make a discussion on the properties of the pion twist-3 DAs.
The ρ-meson light-cone distribution amplitudes from lattice QCD
Braun, Vladimir M.; Bruns, Peter C.; Collins, Sara; Gracey, John A.; Gruber, Michael; Göckeler, Meinulf; Hutzler, Fabian; Pérez-Rubio, Paula; Schäfer, Andreas; Söldner, Wolfgang; Sternbeck, André; Wein, Philipp
2017-04-01
We present the results of a lattice study of the normalization constants and second moments of the light-cone distribution amplitudes of longitudinally and transversely polarized ρ mesons. The calculation is performed using two flavors of dynamical clover fermions at lattice spacings between 0.060 fm and 0.081 fm, different lattice volumes up to m π L = 6.7 and pion masses down to m π = 150 MeV. Bare lattice results are renormalized non-perturbatively using a variant of the RI'-MOM scheme and converted to the \\overline{MS} scheme. The necessary conversion coefficients, which are not available in the literature, are calculated. The chiral extrapolation for the relevant decay constants is worked out in detail. We obtain for the ratio of the tensor and vector coupling constants f ρ T / f ρ = 0.629(8) and the values of the second Gegenbauer moments a 2 ‖ = 0.132(27) and a 2 ⊥ = 0.101(22) at the scale μ = 2 GeV for the longitudinally and transversely polarized ρ mesons, respectively. The errors include the statistical uncertainty and estimates of the systematics arising from renormalization. Discretization errors cannot be estimated reliably and are not included. In this calculation the possibility of ρ → ππ decay at the smaller pion masses is not taken into account.
The pion: an enigma within the Standard Model
Energy Technology Data Exchange (ETDEWEB)
Horn, Tanja; Roberts, Craig D.
2016-05-27
Almost 50 years after the discovery of gluons & quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons, protons, and the pions that bind them. QCD is characterised by two emergent phenomena: confinement & dynamical chiral symmetry breaking (DCSB). They are expressed with great force in the character of the pion. In turn, pion properties suggest that confinement & DCSB are closely connected. As both a Nambu-Goldstone boson and a quark-antiquark bound-state, the pion is unique in Nature. Developing an understanding of its properties is thus critical to revealing basic features of the Standard Model. We describe experimental progress in this direction, made using electromagnetic probes, highlighting both improvements in the precision of charged-pion form factor data, achieved in the past decade, and new results on the neutral-pion transition form factor. Both challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, first explaining how DCSB works to guarantee that the pion is unnaturally light; but also, nevertheless, ensures the pion is key to revealing the mechanisms that generate nearly all the mass of hadrons. Our discussion unifies the charged-pion elastic and neutral-pion transition form factors, and the pion's twist-2 parton distribution amplitude. It also indicates how studies of the charged-kaon form factor can provide significant contributions. Importantly, recent predictions for the large-$Q^2$ behaviour of the pion form factor can be tested by experiments planned at JLab 12. Those experiments will extend precise charged-pion form factor data to momenta that can potentially serve in validating factorisation theorems in QCD, exposing the transition between the nonperturbative and perturbative domains, and thereby reaching a goal that has long driven hadro-particle physics.
Leading Twist Parton Distribution Amplitudes in Heavy Vector Mesons
Directory of Open Access Journals (Sweden)
Gao Fei
2016-01-01
Full Text Available We employed QCD’s Dyson-Schwinger equations (DSEs for heavy quarks and obtained the leading twist parton distribution amplitudes (PDAs in heavy vector mesons J/Ψ and ϒ. We found that all of the amplitudes are narrower than the asymptotic form, while they deviate from δ function. This indicates that the interaction between the two continent quarks are still important in the mesons consisted of charm and bottom quarks.
de Melo, J P B C; El-Bennich, Bruno; Rojas, E; Frederico, T
2014-01-01
Using the light-front pion wave function based on a Bethe-Salpeter amplitude model, we study the properties of the pion in symmetric nuclear matter. The pion model we adopt is well constrained by previous studies to explain the pion properties in vacuum. In order to consistently incorporate the constituent up and down quarks of the pion immersed in symmetric nuclear matter, we use the quark-meson coupling model, which has been widely applied to various hadronic and nuclear phenomena in a nuclear medium with success. We predict the in-medium modifications of the pion lectromagnetic form factor, charge radius and weak decay constant in symmetric nuclear matter.
Parton Distributions Functions of Pion, Kaon and Eta pseudoscalar mesons in the NJL model
Davidson, R M
2002-01-01
Parton distributions of pseudoscalar pi,K and eta mesons obtained within the NJL model using the Pauli-Villars regularization method are analyzed in terms of LO and NLO evolution, and the valence sea quark and gluon parton distributions for the pion are obtained at Q^2 = 4 GeV^2 and compared to existing parametrizations at that scale. Surprisingly, the NLO order effects turn out to be small compared to the LO ones. The valence distributions are in good agreement with experimental analyses, but the gluon and sea distributions come out to be softer in the high-x region and harder in the low-x region than the experimental analyses suggest.
Experimental access to Transition Distribution Amplitudes with the P¯ANDA experiment at FAIR
Singh, B. P.; Erni, W.; Keshelashvili, I.; Krusche, B.; Steinacher, M.; Liu, B.; Liu, H.; Liu, Z.; Shen, X.; Wang, C.; Zhao, J.; Albrecht, M.; Fink, M.; Heinsius, F. H.; Held, T.; Holtmann, T.; Koch, H.; Kopf, B.; Kümmel, M.; Kuhl, G.; Kuhlmann, M.; Leyhe, M.; Mikirtychyants, M.; Musiol, P.; Mustafa, A.; Pelizäus, M.; Pychy, J.; Richter, M.; Schnier, C.; Schröder, T.; Sowa, C.; Steinke, M.; Triffterer, T.; Wiedner, U.; Beck, R.; Hammann, C.; Kaiser, D.; Ketzer, B.; Kube, M.; Mahlberg, P.; Rossbach, M.; Schmidt, C.; Schmitz, R.; Thoma, U.; Walther, D.; Wendel, C.; Wilson, A.; Bianconi, A.; Bragadireanu, M.; Caprini, M.; Pantea, D.; Pietreanu, D.; Vasile, M. E.; Patel, B.; Kaplan, D.; Brandys, P.; Czyzewski, T.; Czyzycki, W.; Domagala, M.; Hawryluk, M.; Filo, G.; Krawczyk, M.; Kwiatkowski, D.; Lisowski, E.; Lisowski, F.; Fiutowski, T.; Idzik, M.; Mindur, B.; Przyborowski, D.; Swientek, K.; Czech, B.; Kliczewski, S.; Korcyl, K.; Kozela, A.; Kulessa, P.; Lebiedowicz, P.; Malgorzata, K.; Pysz, K.; Schäfer, W.; Siudak, R.; Szczurek, A.; Biernat, J.; Jowzaee, S.; Kamys, B.; Kistryn, S.; Korcyl, G.; Krzemien, W.; Magiera, A.; Moskal, P.; Palka, M.; Psyzniak, A.; Rudy, Z.; Salabura, P.; Smyrski, J.; Strzempek, P.; Wrońska, A.; Augustin, I.; Lehmann, I.; Nicmorus, D.; Schepers, G.; Schmitt, L.; Al-Turany, M.; Cahit, U.; Capozza, L.; Dbeyssi, A.; Deppe, H.; Dzhygadlo, R.; Ehret, A.; Flemming, H.; Gerhardt, A.; Götzen, K.; Karabowicz, R.; Kliemt, R.; Kunkel, J.; Kurilla, U.; Lehmann, D.; Lühning, J.; Maas, F.; Morales Morales, C.; Mora Espí, M. C.; Nerling, F.; Orth, H.; Peters, K.; Rodríguez Piñeiro, D.; Saito, N.; Saito, T.; Sánchez Lorente, A.; Schmidt, C. J.; Schwarz, C.; Schwiening, J.; Traxler, M.; Valente, R.; Voss, B.; Wieczorek, P.; Wilms, A.; Zühlsdorf, M.; Abazov, V. M.; Alexeev, G.; Arefiev, A.; Astakhov, V. I.; Barabanov, M. Yu.; Batyunya, B. V.; Davydov, Yu. I.; Dodokhov, V. Kh.; Efremov, A. A.; Fedunov, A. G.; Festchenko, A. A.; Galoyan, A. S.; Grigoryan, S.; Karmokov, A.; Koshurnikov, E. K.; Lobanov, V. I.; Lobanov, Yu. Yu.; Makarov, A. F.; Malinina, L. V.; Malyshev, V. L.; Mustafaev, G. A.; Olshevskiy, A.; Pasyuk, M. A.; Perevalova, E. A.; Piskun, A. A.; Pocheptsov, T. A.; Pontecorvo, G.; Rodionov, V. K.; Rogov, Yu. N.; Salmin, R. A.; Samartsev, A. G.; Sapozhnikov, M. G.; Shabratova, G. S.; Skachkov, N. B.; Skachkova, A. N.; Strokovsky, E. A.; Suleimanov, M. K.; Teshev, R. Sh.; Tokmenin, V. V.; Uzhinsky, V. V.; Vodopyanov, A. S.; Zaporozhets, S. A.; Zhuravlev, N. I.; Zorin, A. G.; Branford, D.; Glazier, D.; Watts, D.; Woods, P.; Britting, A.; Eyrich, W.; Lehmann, A.; Uhlig, F.; Dobbs, S.; Seth, K.; Tomaradze, A.; Xiao, T.; Bettoni, D.; Carassiti, V.; Cotta Ramusino, A.; Dalpiaz, P.; Drago, A.; Fioravanti, E.; Garzia, I.; Savriè, M.; Stancari, G.; Akishina, V.; Kisel, I.; Kulakov, I.; Zyzak, M.; Arora, R.; Bel, T.; Gromliuk, A.; Kalicy, G.; Krebs, M.; Patsyuk, M.; Zuehlsdorf, M.; Bianchi, N.; Gianotti, P.; Guaraldo, C.; Lucherini, V.; Pace, E.; Bersani, A.; Bracco, G.; Macri, M.; Parodi, R. F.; Bianco, S.; Bremer, D.; Brinkmann, K. T.; Diehl, S.; Dormenev, V.; Drexler, P.; Düren, M.; Eissner, T.; Etzelmüller, E.; Föhl, K.; Galuska, M.; Gessler, T.; Gutz, E.; Hayrapetyan, A.; Hu, J.; Kröck, B.; Kühn, W.; Kuske, T.; Lange, S.; Liang, Y.; Merle, O.; Metag, V.; Mülhheim, D.; Münchow, D.; Nanova, M.; Novotny, R.; Pitka, A.; Quagli, T.; Rieke, J.; Rosenbaum, C.; Schnell, R.; Spruck, B.; Stenzel, H.; Thöring, U.; Ullrich, M.; Wasem, T.; Werner, M.; Zaunick, H. G.; Ireland, D.; Rosner, G.; Seitz, B.; Deepak, P. N.; Kulkarni, A. V.; Apostolou, A.; Babai, M.; Kavatsyuk, M.; Lemmens, P.; Lindemulder, M.; Löhner, H.; Messchendorp, J.; Schakel, P.; Smit, H.; van der Weele, J. C.; Tiemens, M.; Veenstra, R.; Vejdani, S.; Kalita, K.; Mohanta, D. P.; Kumar, A.; Roy, A.; Sahoo, R.; Sohlbach, H.; Büscher, M.; Cao, L.; Cebulla, A.; Deermann, D.; Dosdall, R.; Esch, S.; Georgadze, I.; Gillitzer, A.; Goerres, A.; Goldenbaum, F.; Grunwald, D.; Herten, A.; Hu, Q.; Kemmerling, G.; Kleines, H.; Kozlov, V.; Lehrach, A.; Leiber, S.; Maier, R.; Nellen, R.; Ohm, H.; Orfanitski, S.; Prasuhn, D.; Prencipe, E.; Ritman, J.; Schadmand, S.; Schumann, J.; Sefzick, T.; Serdyuk, V.; Sterzenbach, G.; Stockmanns, T.; Wintz, P.; Wüstner, P.; Xu, H.; Li, S.; Li, Z.; Sun, Z.; Xu, H.; Rigato, V.; Fissum, S.; Hansen, K.; Isaksson, L.; Lundin, M.; Schröder, B.; Achenbach, P.; Bleser, S.; Cardinali, M.; Corell, O.; Deiseroth, M.; Denig, A.; Distler, M.; Feldbauer, F.; Fritsch, M.; Jasinski, P.; Hoek, M.; Kangh, D.; Karavdina, A.; Lauth, W.; Leithoff, H.; Merkel, H.; Michel, M.; Motzko, C.; Müller, U.; Noll, O.; Plueger, S.; Pochodzalla, J.; Sanchez, S.; Schlimme, S.; Sfienti, C.; Steinen, M.; Thiel, M.; Weber, T.; Zambrana, M.; Dormenev, V. I.; Fedorov, A. A.; Korzihik, M. V.; Missevitch, O. V.; Balanutsa, P.; Balanutsa, V.; Chernetsky, V.; Demekhin, A.; Dolgolenko, A.; Fedorets, P.; Gerasimov, A.; Goryachev, V.; Varentsov, V.; Boukharov, A.; Malyshev, O.; Marishev, I.; Semenov, A.; Konorov, I.; Paul, S.; Grieser, S.; Hergemöller, A. K.; Khoukaz, A.; Köhler, E.; Täschner, A.; Wessels, J.; Dash, S.; Jadhav, M.; Kumar, S.; Sarin, P.; Varma, R.; Chandratre, V. B.; Datar, V.; Dutta, D.; Jha, V.; Kumawat, H.; Mohanty, A. K.; Roy, B.; Yan, Y.; Chinorat, K.; Khanchai, K.; Ayut, L.; Pornrad, S.; Barnyakov, A. Y.; Blinov, A. E.; Blinov, V. E.; Bobrovnikov, V. S.; Kononov, S. A.; Kravchenko, E. A.; Kuyanov, I. A.; Onuchin, A. P.; Sokolov, A. A.; Tikhonov, Y. A.; Atomssa, E.; Hennino, T.; Imre, M.; Kunne, R.; Le Galliard, C.; Ma, B.; Marchand, D.; Ong, S.; Ramstein, B.; Rosier, P.; Tomasi-Gustafsson, E.; Van de Wiele, J.; Boca, G.; Costanza, S.; Genova, P.; Lavezzi, L.; Montagna, P.; Rotondi, A.; Abramov, V.; Belikov, N.; Bukreeva, S.; Davidenko, A.; Derevschikov, A.; Goncharenko, Y.; Grishin, V.; Kachanov, V.; Kormilitsin, V.; Melnik, Y.; Levin, A.; Minaev, N.; Mochalov, V.; Morozov, D.; Nogach, L.; Poslavskiy, S.; Ryazantsev, A.; Ryzhikov, S.; Semenov, P.; Shein, I.; Uzunian, A.; Vasiliev, A.; Yakutin, A.; Yabsley, B.; Bäck, T.; Cederwall, B.; Makónyi, K.; Tegnér, P. E.; von Würtemberg, K. M.; Belostotski, S.; Gavrilov, G.; Izotov, A.; Kashchuk, A.; Levitskaya, O.; Manaenkov, S.; Miklukho, O.; Naryshkin, Y.; Suvorov, K.; Veretennikov, D.; Zhadanov, A.; Rai, A. K.; Godre, S. S.; Duchat, R.; Amoroso, A.; Bussa, M. P.; Busso, L.; De Mori, F.; Destefanis, M.; Fava, L.; Ferrero, L.; Greco, M.; Maggiora, M.; Maniscalco, G.; Marcello, S.; Sosio, S.; Spataro, S.; Zotti, L.; Calvo, D.; Coli, S.; De Remigis, P.; Filippi, A.; Giraudo, G.; Lusso, S.; Mazza, G.; Mingnore, M.; Rivetti, A.; Wheadon, R.; Balestra, F.; Iazzi, F.; Introzzi, R.; Lavagno, A.; Younis, H.; Birsa, R.; Bradamante, F.; Bressan, A.; Martin, A.; Clement, H.; Gålnander, B.; Caldeira Balkeståhl, L.; Calén, H.; Fransson, K.; Johansson, T.; Kupsc, A.; Marciniewski, P.; Pettersson, J.; Schönning, K.; Wolke, M.; Zlomanczuk, J.; Díaz, J.; Ortiz, A.; Vinodkumar, P. C.; Parmar, A.; Chlopik, A.; Melnychuk, D.; Slowinski, B.; Trzcinski, A.; Wojciechowski, M.; Wronka, S.; Zwieglinski, B.; Bühler, P.; Marton, J.; Suzuki, K.; Widmann, E.; Zmeskal, J.; Fröhlich, B.; Khaneft, D.; Lin, D.; Zimmermann, I.; Semenov-Tian-Shansky, K.
2015-08-01
Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion ( πN) TDAs from reaction with the future P¯ANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q 2, the amplitude of the signal channel admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring with the P¯ANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q 2 < 4.3 GeV2 and 5 < q 2 GeV2, respectively, with a neutral pion scattered in the forward or backward cone in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the P¯ANDA detector will allow to achieve a background rejection factor of 5 · 107 (1 · 107) at low (high) q 2 for s = 5 GeV2, and of 1 · 108 (6 · 106) at low (high) q 2 for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb-1 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with P¯ANDA will provide a new test of the perturbative QCD description of a novel class of hard
Flavour dependence of the pion and kaon form factors and parton distribution functions
Hutauruk, Parada T P; Thomas, Anthony W
2016-01-01
The separate quark flavour contributions to the pion and kaon valence quark distribution functions are studied, along with the corresponding electromagnetic form factors in the space-like region. The calculations are made using the solution of the Bethe-Salpeter equation for the model of Nambu and Jona-Lasinio with proper-time regularization. Both the pion and kaon form factors and the valence quark distribution functions reproduce many of the features of the available empirical data. The larger mass if the strange quark naturally explains the empirical fact that the ratio $u_{K^+}(x)/u_{\\pi^+}(x)$ drops below unity at large $x$, with a value of approximately $M^2_u/M_s^2$ as $x \\to 1$. With regard to the elastic form factors we report a large flavour dependence, with the $u$-quark contribution to the kaon form factor being an order of magnitude smaller than that of the $s$-quark at large $Q^2$, which may be a sensitive measure of confinement effects in QCD. Surprisingly though, the total $K^+$ and $\\pi^+$ fo...
Frederico, T; Pasquini, B; Salme', G
2009-01-01
The generalized parton distributions of the pion are studied within different light-front approaches for the quark-hadron and quark-photon vertices, exploring different kinematical regions in both the valence and non-valence sector. Moments of the generalized parton distributions which enter the definition of generalized form factors are also compared with recent lattice calculations.
Baryon to meson transition distribution amplitudes and their spectral representation
Pire, Bernard; Szymanowski, Lech
2011-01-01
We consider the problem of construction of a spectral representation for nucleon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of nonlocal three quark light-cone operators between a nucleon and a meson states. We introduce the notion of quadruple distributions and generalize Radyshkin's factorized Ansatz for this issue. Modelling of baryon to meson TDAs in the complete domain of their definition opens the way to quantitative estimates of cross-sections for various hard exclusive reactions.
Baryon-to-meson transition distribution amplitudes: formalism and models
Pire, B; Szymanowski, L
2016-01-01
In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.
Baryon-to-Meson Transition Distribution Amplitudes: Formalism and Models
Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.
2017-03-01
In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.
Generalized quantum counting algorithm for non-uniform amplitude distribution
Tan, Jianing; Ruan, Yue; Li, Xi; Chen, Hanwu
2017-03-01
We give generalized quantum counting algorithm to increase universality of quantum counting algorithm. Non-uniform initial amplitude distribution is possible due to the diversity of situations on counting problems or external noise in the amplitude initialization procedure. We give the reason why quantum counting algorithm is invalid on this situation. By modeling in three-dimensional space spanned by unmarked state, marked state and free state to the entire Hilbert space of n qubits, we find Grover iteration can be regarded as improper rotation in the space. This allows us to give formula to solve counting problem. Furthermore, we express initial amplitude distribution in the eigenvector basis of improper rotation matrix. This is necessary to obtain mathematical analysis of counting problem on various situations. Finally, we design four simulation experiments, the results of which show that compared with original quantum counting algorithm, generalized quantum counting algorithm wins great satisfaction from three aspects: (1) Whether initial amplitude distribution is uniform; (2) the diversity of situations on counting problems; and (3) whether phase estimation technique can get phase exactly.
Analytic Evolution of Singular Distribution Amplitudes in QCD
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, Anatoly V. [Old Dominion University, Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Tandogan Kunkel, Asli [Old Dominion University, Norfolk, VA (United States); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
2014-03-01
We describe a method of analytic evolution of distribution amplitudes (DA) that have singularities, such as non-zero values at the end-points of the support region, jumps at some points inside the support region and cusps. We illustrate the method by applying it to the evolution of a flat (constant) DA, anti-symmetric at DA and then use it for evolution of the two-photon generalized distribution amplitude. Our approach has advantages over the standard method of expansion in Gegenbauer polynomials, which requires infinite number of terms in order to accurately reproduce functions in the vicinity of singular points, and over a straightforward iteration of an initial distribution with evolution kernel. The latter produces logarithmically divergent terms at each iteration, while in our method the logarithmic singularities are summed from the start, which immediately produces a continuous curve, with only one or two iterations needed afterwards in order to get rather precise results.
Spin effects in the pion holographic light-front wavefunction
Ahmady, Mohammad; Sandapen, Ruben
2016-01-01
We account for dynamical spin effects in the holographic light-front wavefunction of the pion in order to predict its mean charge radius, decay constant, spacelike electromagnetic form factor, twist-2 Distribution Amplitude and the photon-to-pion transition form factor. Using a universal fundamental AdS/QCD scale of 523 MeV and a constituent quark mass of 330 MeV, we find a remarkable improvement in describing all observables.
Braun, V M; Gläßle, B; Göckeler, M; Schäfer, A; Schiel, R W; Söldner, W; Sternbeck, A; Wein, P
2014-01-01
We present the results of a lattice study of light-cone distribution amplitudes (DAs) of the nucleon and negative parity nucleon resonances using two flavors of dynamical (clover) fermions on lattices of different volumes and pion masses down to m_pi = 150 MeV. We find that the three valence quarks in the proton share their momentum in the proportion 37% : 31% : 31%, where the larger fraction corresponds to the u-quark that carries proton helicity, and determine the value of the wave function at the origin in position space, which turns out to be small compared to the existing estimates based on QCD sum rules. Higher-order moments are constrained by our data and are all compatible with zero within our uncertainties. We also calculate the normalization constants of the higher-twist DAs that are related to the distribution of quark angular momentum. Furthermore, we use the variational method and customized parity projection operators to study the states with negative parity. In this way we are able to separate ...
Elastic Scattering of Low Energy Pions by Nuclei and the In-Medium Isovector πN Amplitude
Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Kritchman, S.; Meier, R.; Wagner, G. J.; Yaari, G.
2006-07-01
Measurements of elastic scattering of 21.5 MeV π± by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer and absolute calibration was made by parallel measurements of Coulomb scattering of muons. Optical model fits to the data reveal the `anomalous' s-wave repulsion known from pionic atoms. Introducing a chiral-motivated density dependence of the isovector scattering amplitude, and considering the energy dependence of the free πN interaction greatly improve fits to the data and remove the `anomaly'.
Analytic Evolution of Singular Distribution Amplitudes in QCD
Energy Technology Data Exchange (ETDEWEB)
Tandogan Kunkel, Asli [Old Dominion Univ., Norfolk, VA (United States)
2014-08-01
Distribution amplitudes (DAs) are the basic functions that contain information about the quark momentum. DAs are necessary to describe hard exclusive processes in quantum chromodynamics. We describe a method of analytic evolution of DAs that have singularities such as nonzero values at the end points of the support region, jumps at some points inside the support region and cusps. We illustrate the method by applying it to the evolution of a at (constant) DA, antisymmetric at DA, and then use the method for evolution of the two-photon generalized distribution amplitude. Our approach to DA evolution has advantages over the standard method of expansion in Gegenbauer polynomials [1, 2] and over a straightforward iteration of an initial distribution with evolution kernel. Expansion in Gegenbauer polynomials requires an infinite number of terms in order to accurately reproduce functions in the vicinity of singular points. Straightforward iteration of an initial distribution produces logarithmically divergent terms at each iteration. In our method the logarithmic singularities are summed from the start, which immediately produces a continuous curve. Afterwards, in order to get precise results, only one or two iterations are needed.
Renormalization and applications of baryon distribution amplitudes QCD
Energy Technology Data Exchange (ETDEWEB)
Rohrwild, Juergen Holger
2009-07-17
Higher-twist effects are relevant for precision calculations of hard exclusive reactions. Furthermore, they reveal fine details of the hadron structure. In this work we construct an operator basis for arbitrary twist respecting the conformal symmetry of QCD (which is realized on 1-loop level). Using this basis the 1-loop renormalization kernels of twist 4 are constructed for baryon operators. The full spectrum of anomalous dimensions and the multiplicatively renormalizable operators is obtained. As an application of these results the radiative N{sup *}(1535) decay is discussed. Employing light-cone sum rule, the transition form factors can be directly related to the N{sup *} distribution amplitudes. (orig.)
Renormalization and applications of baryon distribution amplitudes in QCD
Energy Technology Data Exchange (ETDEWEB)
Rohrwild, Juergen Holger
2009-07-17
Higher-twist effects are relevant for precision calculations of hard exclusive reactions. Furthermore, they reveal fine details of the hadron structure. In this work we construct an operator basis for arbitrary twist respecting the conformal symmetry of QCD (which is realized on 1-loop level). Using this basis the 1-loop renormalization kernels of twist 4 are constructed for baryon operators. The full spectrum of anomalous dimensions and the multiplicatively renormalizable operators is obtained. As an application of these results the radiative N{sup *}(1535) decay is discussed. Employing light-cone sum rule, the transition form factors can be directly related to the N* distribution amplitudes. (orig.)
Lattice results for low moments of light meson distribution amplitudes
Energy Technology Data Exchange (ETDEWEB)
Arthur, R.; Boyle, P.A. [Edinburgh Univ. (United Kingdom). SUPA, School of Physics; Broemmel, D.; Flynn, J.M.; Rae, T.D.; Sachrajda, C.T.C. [Southampton Univ. (United Kingdom). School of Physics and Astronomy; Donnellan, M.A. [NIC/DESY Zeuthen (Germany); Juettner, A. [CERN, Geneva (Switzerland). Physics Dept.
2010-12-15
As part of the UKQCD and RBC collaborations' N{sub f} = 2+1 domain-wall fermion phenomenology programme, we calculate the first two moments of the light-cone distribution amplitudes of the pseudoscalar mesons {pi} and K and the (longitudinally-polarised) vector mesons {rho}, K{sup *} and {phi}. We obtain the desired quantities with good precision and are able to discern the expected quark-mass dependence of SU(3)-flavour breaking effects. An important ingredient of the calculation is the nonperturbative renormalisation of lattice operators using the RI{sup '}/MOM technique. (orig.)
Pion Induced Pion Production on Deuterium.
Sossi, Vesna
This thesis describes measurements of the pion induced pion production reaction pi^+ d to pi^{+} pi^{-}p p performed with a 280 MeV incident pi^{+} beam at TRIUMF. The data are compared with an improved version of the Oset and Vicente-Vacas theoretical model (12). The goal of the experiment and of the analysis was to provide a larger body of data for the free reaction and to test the validity of theoretical models. In the process, the ability to determine the values of the coupling constants C, f_Delta, g _{N*Delta_tau} within such a model framework would be explored. The knowledge of the precise value of these coupling constants would constrain N^* decay branching ratios and other pion induced reaction mechanisms like Double Charge Exchange. A previous experiment (23) had indicated that the pion induced pion production on deuterium is essentially a quasifree process with the reaction occurring on the neutron leaving the proton merely a spectator. The main difference with respect to the free reaction is the effect of Fermi motion of the neutron. Although we were interested in studying the free reaction (pi^ {-}p to pi^ {+}pi^{-}n), we chose a deuterium target so that the experiment could be run with a pi^+beam, since the pi^- beam flux is about 6 times lower than the flux of the positive pion beam at 280 MeV, the energy at which our experiment was performed. Such a flux would have required a much longer running time for the experiment in order to achieve the same statistical accuracy. The quasifree nature of the process was also confirmed in our experiment. This experiment involved a coincidence measurement of the quasifree process and as such provided four-fold differential cross section spectra of the reaction thus allowing for a microscopic comparison between data and theoretical models. In the theoretical description we incorporated additional amplitudes for the N^* to N(pipi)_{p-wave} diagrams required to describe the reaction cross section at T_pi = 280 Me
Energy Technology Data Exchange (ETDEWEB)
Huang, Z. [Department of Physics, University of Arizona, Tucson, Arizona 85741 (United States); Suzuki, M. [Department of Physics and Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 (United States)
1996-01-01
We obtain the general solutions of the nonlinear {sigma} model in 3+1 dimensions as the candidates for the disoriented chiral condensate (DCC). The nonuniformly isospin-oriented solutions are shown to be related to the uniformly oriented ones through the chiral (axial) rotations. We discuss the pion charge distribution arising from these solutions. The distribution {ital dP}/{ital d}{ital f}=1/(2 {radical}{ital f} ) holds for the uniform solutions in general and the nonuniform solutions in the 1+1 boost-invariant case. For the nonuniform solution in 1+1 without boost invariance and in higher dimensions, the distribution does not hold in the integrated form. However, it is applicable to the pions selected from a small segment in the momentum phase space. We suggest that the nonuniform DCC{close_quote}s may correspond to the mini-Centauro events. {copyright} {ital 1996 The American Physical Society.}
Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
Energy Technology Data Exchange (ETDEWEB)
Singh, B.P. [Aligarh Muslim Univ. (India). Physics Dept.; Erni, W.; Keshelashvili, I. [Basel Univ. (Switzerland); Collaboration: The PANDA Collaboration; and others
2015-08-15
Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (πN) TDAs from anti pp → e{sup +}e{sup -}π{sup 0} reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q{sup 2}, the amplitude of the signal channel anti pp → e{sup +}e{sup -}π{sup 0} admits a QCD factorized description in terms of πN TDAs and nucleon Distribution Amplitudes (DAs) in the forward and backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring anti pp → e{sup +}e{sup -}π{sup 0} with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. anti pp → π{sup +}π{sup -}π{sup 0} were performed for the center-of-mass energy squared s = 5 GeV{sup 2} and s = 10 GeV{sup 2}, in the kinematic regions 3.0 < q{sup 2} < 4.3 GeV{sup 2} and 5 < q{sup 2} GeV{sup 2}, respectively, with a neutral pion scattered in the forward or backward cone vertical stroke cos θ{sub π{sup 0}} vertical stroke > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10{sup 7} (1 . 10{sup 7}) at low (high) q{sup 2} for s = 5 GeV{sup 2}, and of 1 . 10{sup 8} (6 . 10{sup 6}) at low (high) q{sup 2} for s = 10 GeV{sup 2}, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 fb{sup -1} of integrated luminosity. The cross sections obtained from the simulations are used to
Reconstruction of far-field tsunami amplitude distributions from earthquake sources
Geist, Eric L.; Parsons, Thomas E.
2016-01-01
The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.
Reconstruction of Far-Field Tsunami Amplitude Distributions from Earthquake Sources
Geist, Eric L.; Parsons, Tom
2016-04-01
The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.
Reconstruction of Far-Field Tsunami Amplitude Distributions from Earthquake Sources
Geist, Eric L.; Parsons, Tom
2016-12-01
The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.
Amplitude Distribution of Emission Wave for Cracking Process
Directory of Open Access Journals (Sweden)
Shahidan Shahiron
2016-01-01
Full Text Available Acoustic emission technique is a method of assessment for structural health monitoring system. This technique is an effective tool for the evaluation of any system without destroying the material conditions. It enables early crack detections and has very high sensitivity to crack growth. The crack patterns in concrete beam have been identified according to the type of cracking process and the crack classifications using the AE data parameters are mainly based on the AE amplitude, rise time, and average frequency. These data parameters have been analysed using statistical methods of b-value analysis. This research paper will mainly focus on the utilization of statistical b-value analysis in evaluating the emission amplitude distribution of concrete beams. The beam specimens (150 × 250 × 1900 mm were prepared in the laboratory system and tested with the four point bending test using cyclic loading together with acoustic emission monitoring system. The results showed that this statistical analysis is promising in determining the cracking process in concrete beams.
The pion: an enigma within the Standard Model
Horn, Tanja; Roberts, Craig D.
2016-07-01
Quantum chromodynamics (QCDs) is the strongly interacting part of the Standard Model. It is supposed to describe all of nuclear physics; and yet, almost 50 years after the discovery of gluons and quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons and protons, and the pions that bind them together. QCD is characterised by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB). They have far-reaching consequences, expressed with great force in the character of the pion; and pion properties, in turn, suggest that confinement and DCSB are intimately connected. Indeed, since the pion is both a Nambu-Goldstone boson and a quark-antiquark bound-state, it holds a unique position in nature and, consequently, developing an understanding of its properties is critical to revealing some very basic features of the Standard Model. We describe experimental progress toward meeting this challenge that has been made using electromagnetic probes, highlighting both dramatic improvements in the precision of charged-pion form factor data that have been achieved in the past decade and new results on the neutral-pion transition form factor, both of which challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, which begins with an explanation of how DCSB works to guarantee that the pion is un-naturally light; but also, nevertheless, ensures that the pion is the best object to study in order to reveal the mechanisms that generate nearly all the mass of hadrons. In canvassing advances in these areas, our discussion unifies many aspects of pion structure and interactions, connecting the charged-pion elastic form factor, the neutral-pion transition form factor and the pion's leading-twist parton distribution amplitude. It also sketches novel ways in which experimental and theoretical studies of the charged-kaon electromagnetic form factor can provide
The pion: an enigma within the Standard Model
Energy Technology Data Exchange (ETDEWEB)
Horn, Tanja; Roberts, Craig D.
2016-05-27
Quantum chromodynamics (QCDs) is the strongly interacting part of the Standard Model. It is supposed to describe all of nuclear physics; and yet, almost 50 years after the discovery of gluons and quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons and protons, and the pions that bind them together. QCD is characterised by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB). They have far-reaching consequences, expressed with great force in the character of the pion; and pion properties, in turn, suggest that confinement and DCSB are intimately connected. Indeed, since the pion is both a Nambu–Goldstone boson and a quark–antiquark bound-state, it holds a unique position in nature and, consequently, developing an understanding of its properties is critical to revealing some very basic features of the Standard Model. We describe experimental progress toward meeting this challenge that has been made using electromagnetic probes, highlighting both dramatic improvements in the precision of charged-pion form factor data that have been achieved in the past decade and new results on the neutral-pion transition form factor, both of which challenge existing notions of pion structure. We also provide a theoretical context for these empirical advances, which begins with an explanation of how DCSB works to guarantee that the pion is un-naturally light; but also, nevertheless, ensures that the pion is the best object to study in order to reveal the mechanisms that generate nearly all the mass of hadrons. In canvassing advances in these areas, our discussion unifies many aspects of pion structure and interactions, connecting the charged-pion elastic form factor, the neutral-pion transition form factor and the pion's leading-twist parton distribution amplitude. It also sketches novel ways in which experimental and theoretical studies of the charged-kaon electromagnetic form factor can provide
Light-Cone Distribution Amplitudes for Heavy-Quark Hadrons
Bell, Guido; Wang, Yu-Ming; Yip, Matthew W Y
2013-01-01
We construct parametrizations of light-cone distribution amplitudes (LCDAs) for B-mesons and Lambda_b-baryons that obey various theoretical constraints, and which are simple to use in factorization theorems relevant for phenomenological applications in heavy-flavour physics. In particular, we find the eigenfunctions of the Lange-Neubert renormalization kernel, which allow for a systematic implementation of renormalization-group evolution effects for both B-meson and \\Lambda_b-baryon decays. We also present a new strategy to construct LCDA models from momentum-space projectors, which can be used to implement Wandzura-Wilczek--like relations, and which allow for a comparison with theoretical approaches that go beyond the collinear limit for the light-quark momenta in energetic heavy-hadron decays.
Method of Analytic Evolution of Flat Distribution Amplitudes in QCD
Tandogan, Asli
2011-01-01
A new analytical method of performing ERBL evolution is described. The main goal is to develop an approach that works for distribution amplitudes that do not vanish at the end points, for which the standard method of expansion in Gegenbauer polynomials is inefficient. Two cases of the initial DA are considered: a purely flat DA, given by the same constant for all x, and an antisymmetric DA given by opposite constants for x 1/2. For a purely flat DA, the evolution is governed by an overall (x (1-x))^t dependence on the evolution parameter t times a factor that was calculated as an expansion in t. For an antisymmetric flat DA, an extra overall factor |1-2x|^{2t} appears due to a jump at x=1/2. A good convergence was observed in the t < 1/2 region. For larger t, one can use the standard method of the Gegenbauer expansion.
The ρ-meson longitudinal leading-twist distribution amplitude
Directory of Open Access Journals (Sweden)
Hai-Bing Fu
2014-11-01
Full Text Available In the present paper, we suggest a convenient model for the vector ρ-meson longitudinal leading-twist distribution amplitude ϕ2;ρ‖, whose distribution is controlled by a single parameter B2;ρ‖. By choosing proper chiral current in the correlator, we obtain new light-cone sum rules (LCSR for the B→ρ TFFs A1, A2 and V, in which the δ1-order ϕ2;ρ‖ provides dominant contributions. Then we make a detailed discussion on the ϕ2;ρ‖ properties via those B→ρ TFFs. A proper choice of B2;ρ‖ can make all the TFFs agree with the lattice QCD predictions. A prediction of |Vub| has also been presented by using the extrapolated TFFs, which indicates that a larger B2;ρ‖ leads to a larger |Vub|. To compare with the BABAR data on |Vub|, the longitudinal leading-twist DA ϕ2;ρ‖ prefers a doubly-humped behavior.
Pion Structure at High and Low Energies in Chiral Quark Models
Ruiz-Arriola, E
2002-01-01
Low and high energy properties of the pion are reviewed in the framework of chiral quark models. Particular emphasis is put on the simplest version of the SU(2) NJL model as prototype. The role of gauge invariance in this kind of calculations is stressed. The results are used as initial conditions for perturbative QCD evolution equations. At leading order the quark model scale is $\\mu_0 \\sim 320 {\\rm MeV} $ as determined from the pion distribution functions and the pion distribution amplitudes.
Leading-twist distribution amplitudes of scalar and vector mesons
Li, B.-L.; Chang, L.; Ding, M.; Roberts, C. D.; Zong, H.-S.
2016-11-01
A symmetry-preserving truncation of the two-body light-quark bound-state problem in relativistic quantum field theory is used to calculate the leading-twist parton distribution amplitudes (PDAs) of scalar systems, both ground-state and radial excitations, and the radial excitations of vector mesons. Owing to the fact that the scale-independent leptonic decay constant of a scalar meson constituted from equal-mass valence constituents vanishes, it is found that the PDA of a given scalar system possesses one more zero than that of an analogous vector meson. Consequently, whereas the mean light-front relative momentum of the valence constituents within a vector meson is zero, that within a scalar meson is large, an outcome which hints at a greater role for light-front angular momentum in systems classified as P -wave in quantum mechanical models. Values for the scale-dependent decay constants of ground-state scalar and vector systems are a by-product of this analysis, and they turn out to be roughly equal, viz. ≃0.2 GeV at an hadronic scale. In addition, it is confirmed that the dilation characterizing ground-state PDAs is manifest in the PDAs of radial excitations too. The impact of S U (3 )-flavor symmetry breaking is also considered. When compared with pseudoscalar states, it is a little stronger in scalar systems, but the size is nevertheless determined by the flavor dependence of dynamical chiral symmetry breaking and the PDAs are still skewed toward the heavier valence quark in asymmetric systems.
Flores, Christopher E.
2016-12-01
The Beam Energy Scan (BES) at the Relativistic Heavy-Ion Collider was proposed to characterize the properties of the medium produced in heavy-ion interactions over a broad range of baryon chemical potential. The aptitude of the STAR detector for mid-rapidity measurements has previously been leveraged to measure identified particle yields and spectra to extract bulk properties for the BES energies for | y | ≤ 0.1. However, to extract information on expansion dynamics and full phase space particle production, it is necessary to study identified particle rapidity density distributions. We present the first rapidity density distributions of identified pions from Au+Au collisions at √{sNN} = 7.7 , 11.5, and 19.6 GeV from the BES program as measured by the STAR detector. We use these distributions to obtain the full phase space yields of the pions to provide additional information of the system's chemistry. Further, we report the width of the rapidity density distributions compared to the width expected from Landau hydrodynamics. Finally, we interpret the results as a function of collision energy and discuss them in the context of previous energy scans done at the AGS and SPS.
Adriani, O.; Bonechi, L.; Bongi, M.; D'Alessandro, R.; Del Prete, M.; Haguenauer, M.; Itow, Y.; Kasahara, K.; Kawade, K.; Makino, Y.; Masuda, K.; Matsubayashi, E.; Menjo, H.; Mitsuka, G.; Muraki, Y.; Papini, P.; Perrot, A.L.; Ricciarini, S.; Sako, T.; Sakurai, N.; Suzuki, T.; Tamura, T.; Tiberio, A.; Torii, S.; Tricomi, A.; Turner, W.C.; Zhou, Q.D.
2016-01-01
The transverse and longitudinal momentum distributions for inclusive neutral pions in the very forward rapidity region have been measured with the Large Hadron Collider forward detector in proton-proton collisions at $\\sqrt{s}=$ 2.76 and 7 TeV and in proton-lead collisions at nucleon-nucleon center-of-mass energies of $\\sqrt{s_\\text{NN}}=$ 5.02 TeV at the LHC. Such momentum distributions in proton-proton collisions are compatible with the hypotheses of limiting fragmentation and Feynman scaling. A sizable suppression of the production of neutral pions, after taking into account ultraperipheral collisions, is found in the transverse and longitudinal momentum distributions obtained in proton-lead collisions. This leads to a strong nuclear modification factor value of about 0.1-0.3. The experimental measurements presented in this paper provide a benchmark for the hadronic interaction Monte Carlo simulations codes that are used for the simulation of air showers.
Pchelkin, Vladimir; Beloglazov, Mikhail
The distributions of the amplitudes of natural emissions of electromagnetic field in the Shu-mann resonance frequency range are investigated. From the data of Lovozero observatory daily variations of the number of overshoots of signal amplitude above given thresholds were con-structed. A possibility is discussed of applicability for the considered frequency range a known from the literature formula, which describes analytically the peak distribution of the spherics. We note the influence of magnetic disturbances on amplitude distribution function.
Koers, H B J; Wijers, R A M J; Koers, Hylke B. J.; Pe'er, Asaf; Wijers, Ralph A. M. J.
2006-01-01
The possibility of proton acceleration to very high energies in astrophysical sources may have unique observational consequences. In particular, the decay of secondary mesons created in the interaction of energetic protons with photons or nucleons gives rise to high-energy gamma rays and neutrinos with potentially observable fluxes. Recently, there has been considerable interest in the parameterization of the energy spectra of these secondaries. Less attention has been paid to the angular distributions, which may have an important effect on observational quantities and are required to address collisions between protons with different energies and an arbitrary scattering angle. In this work, we study the complete particle distributions of secondary mesons created in proton-proton collisions. We present parameterizations of the energy and rapidity distributions of secondary pions and kaons that reproduce results generated with the event generator PYTHIA to within ~10% in the bulk of the parameter space. The par...
Crossing symmetric potential model of pion-nucleon scattering
Blankleider, B; Skawronski, T
2010-01-01
A crossing symmetric $\\pi N$ scattering amplitude is constructed through a complete attachment of two external pions to the dressed nucleon propagator of an underlying $\\pi N$ potential model. Our formulation automatically provides expressions also for the crossing symmetric and gauge invariant pion photoproduction and Compton scattering amplitudes. We show that our amplitudes are unitary if they coincide on-shell with the amplitudes obtained by attaching one pion to the dressed $\\pi NN$ vertex of the same potential model.
Energy Technology Data Exchange (ETDEWEB)
Busza, W.; Luckey, D.; Votta, L.; Young, C.; Halliwell, C.; Elias, J.
1976-01-01
Multiparticle production in hadron-nucleus collisions has been studied using hodoscope arrays. Data on angular distributions were collected for incident ..pi../sup + -/, K/sup + -/, and P/sup + -/ at 50, 100, and 200 GeV with targets ranging from hydrogen through uranium. The extent in pseudo-rapidity of particles produced in the target fragmentation region increases with energy. Proton and pion induced reactions exhibit different behavior for the same target nucleus. However, for target nuclei with identical values of ..nu..bar, (where ..nu..bar is the average thickness in units of the mean free path of the incident particle) the behavior is similar. Pseudo-rapidity distributions are compared with theoretical models.
Chiral perturbation theory for generalized parton distributions and baryon distribution amplitudes
Energy Technology Data Exchange (ETDEWEB)
Wein, Philipp
2016-05-06
In this thesis we apply low-energy effective field theory to the first moments of generalized parton distributions and to baryon distribution amplitudes, which are both highly relevant for the parametrization of the nonperturbative part in hard processes. These quantities yield complementary information on hadron structure, since the former treat hadrons as a whole and, thus, give information about the (angular) momentum carried by an entire parton species on average, while the latter parametrize the momentum distribution within an individual Fock state. By performing one-loop calculations within covariant baryon chiral perturbation theory, we obtain sensible parametrizations of the quark mass dependence that are ideally suited for the subsequent analysis of lattice QCD data.
Paakkinen, Petja; Paukkunen, Hannu
2016-01-01
Despite the success of modern nuclear parton distribution functions (nPDFs) in describing nuclear hard-process data, they still suffer from large uncertainties. One of the poorly constrained features is the possible asymmetry in nuclear modifications of valence $u$ and $d$ quarks. We study the possibility of using pion-nucleus Drell-Yan dilepton data as a new constraint in the global analysis of nPDFs. We find that the nuclear cross-section ratios from the NA3, NA10 and E615 experiments can be used without imposing significant new theoretical uncertainties and, in particular, that these datasets may have some constraining power on the $u$/$d$ -asymmetry in nuclei.
Light-cone distribution amplitudes of the ground state bottom baryons in HQET
Energy Technology Data Exchange (ETDEWEB)
Ali, A.; Wang, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hambrock, C. [Technische Univ. Dortmund (Germany); Parkhomenko, A.Ya. [P.G. Demidov Yaroslavl State Univ., Yaroslavl (Russian Federation)
2012-12-15
We provide the definition of the complete set of light-cone distribution amplitudes (LCDAs) for the ground state heavy bottom baryons with the spin-parities J{sup P}=1/2{sup +} and J{sup P}=3/2{sup +} in the heavy quark limit. We present the renormalization effects on the twist-2 light-cone distribution amplitudes and use the QCD sum rules to compute the moments of twist-2, twist-3, and twist-4 LCDAs. Simple models for the heavy baryon distribution amplitudes are analyzed with account of their scale dependence.
The Most Likely Distribution of Target Echo Amplitudes
Moll, C.A.M. van; Ainslie, M.A.; Janmaat, J.
2007-01-01
Whether for sonar performance modelling or for performance optimisation, the detection and false alarm probabilities of a sonar system must be determined. An accurate calculation of both probabilities requires knowledge of the distributions of signal and noise. The scope of this article is limited t
Tremor and its duration-amplitude distribution at Popocatépetl volcano, Mexico
Arámbula-Mendoza, R.; Valdés-González, C.; Varley, N.; Reyes-Pimentel, T. A.; Juárez-García, B.
2016-09-01
The duration-amplitude distribution was calculated for the tremor observed at Popocatépetl volcano during episodes of activity in 2000 and 2012-2014. An exponential function was used to obtain a good fit for the duration-amplitude distribution, and the source of volcanic tremor is probably generated by the transportation of magmatic fluids and its coupling with the host rock within the volcanic conduit. In particular, harmonic tremor has shown large amplitudes, durations, and mean values of amplitude, more than spasmodic or pulsating tremor. This is due to different generation mechanisms: in the case of harmonic tremor, it is produced during magma ascent and lava dome growth, while spasmodic and pulsating tremors are associated with fragmentation of the lava dome and gas emissions. This paper presents the duration-amplitude distribution as a method to estimate the intensity of the tremor at Popocatépetl, a volcano with the major risk in all Mexico.
Exclusive measurements of pion nucleon going to pion pion nucleon
Kermani, Mohammad Arjomand
The pion induced pion production reactions π±p/toπ±π+n were studied at projectile incident energies of 223, 243, 264, 284, and 305 MeV. The Canadian High Acceptance Orbit Spectrometer (CHAOS) was used to detected the charged particles, which originated from the interaction of the incident pion beam with a cryogenic liquid hydrogen target. The experimental results are presented in the form of single, double and triple differential cross sections. Total cross sections obtained by integrating the differential quantities are also reported. The experimental data, namely the π-p/toπ-π+n double differential cross sections, were used as input to the Chew-Low extrapolation procedure which was utilized to determine on-shell π+π- elastic scattering cross sections in the near threshold region. The Chew-Low results (the extrapolated πpi cross sections) were then used in a dispersion analysis (Roy equations) to obtain the πpi isospin zero S-wave scattering length. We find a00=0.209/pm 0.011μ-1. In addition, the invariant mass distributions from the (π+π-) channel were fitted to determine the model parameters for the extended model of Oset and Vicente-Vacas. We find that the model parameters obtained from fitting the (π+π-) data do not describe the invariant mass distributions in the (π+π+) channel.
Backward pion-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Huang, F. [Univ. of Georgia, Athens, GA (United States); Sibirtsev, Alex [Helmholtz-Institut furr Strahlen- und Kernphysik (Theorie) und Bethe Center for Theoretical Physics, Universitat Bonn, D-53115 Bonn, Germany; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Haidenbauer, Johann [Forschungszentrum Julich (Germany); Meissner, Ulf-G. [Helmholtz-Institut fur Strahlen- und Kernphysik (Theorie) und Bethe Center for Theoretical Physics, Universitat Bonn, Bonn, Germany; Forschungszentrum Julich (Germany)
2010-02-01
A global analysis of the world data on differential cross sections and polarization asymmetries of backward pion-nucleon scattering for invariant collision energies above 3 GeV is performed in a Regge model. Including the $N_\\alpha$, $N_\\gamma$, $\\Delta_\\delta$ and $\\Delta_\\beta$ trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable $u$, in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below 3 GeV. Our analysis suggests a $G_{39}$ resonance with a mass of 2.83 GeV as member of the $\\Delta_{\\beta}$ trajectory from the corresponding Chew-Frautschi plot.
πN TDAs from charmonium production in association with a forward pion at P̅ANDA
Directory of Open Access Journals (Sweden)
Ma B.
2014-06-01
Full Text Available Charmonium production in association with a forward or backward pion in nucleon-antinucleon annihilation is one of the most promising reaction to access nucleon-to-pion transition distribution amplitudes (TDAs at P̅ANDA. We briefly review the description of this reaction in terms of πN TDAs within the collinear factorization approach and present the first results of dedicated feasibility studies for the P̅ANDA experimental setup.
Pion rescattering in two-pion decay of heavy quarkonia
Lähde, T A
2002-01-01
The role of pion rescattering in pi pi decay of radially excited heavy quarkonia modeled in terms of a Q pi pi coupling, is investigated within the framework of the covariant Blankenbecler-Sugar equation. The effects of pion rescattering (or pion exchange) are shown to be large, unless the coupling of the two-pion system to the heavy quarks is mediated by a fairly light scalar sigma meson, which couples to the gradients of the pion fields. The Hamiltonian model for the quarkonium states is formed of linear scalar confining, screened one-gluon exchange and instanton induced interaction terms. The widths and energy distributions of the basic decays psi'->J/psi pi pi and UPSILON'-> UPSILON pi pi are shown to be satisfactorily described by this model. The implications of this model for the decays of the UPSILON(3S) state are discussed.
Effect of attenuation correction on surface amplitude distribution of wind waves
Digital Repository Service at National Institute of Oceanography (India)
Varkey, M.J.
Some selected wave profiles recorded using a ship borne wave recorder are analysed to study the effect of attenuation correction on the distribution of the surface amplitudes. A new spectral width parameter is defined to account for wide band...
Vector-pseudoscalar two-meson distribution amplitudes in three-body $B$ meson decays
Chen Chuan Hung; Chen, Chuan-Hung; Li, Hsiang-nan
2004-01-01
We study three-body nonleptonic decays $B\\to VVP$ by introducing two-meson distribution amplitudes for the vector-pseudoscalar pair, such that the analysis is simplified into the one for two-body decays. The twist-2 and twist-3 $\\phi K$ two-meson distribution amplitudes, associated with longitudinally and transversally polarized $\\phi$ mesons, are constrained by the experimental data of the $\\tau\\to\\phi K\
Decay Constants and Distribution Amplitudes of B Meson in the Relativistic Potential Model
Sun, Hao-Kai
2016-01-01
In this work we study the decay constants of $B$ and $B_s$ mesons based on the wave function obtained in the relativistic potential model. Our results are in good agreement with experiment data which enables us to apply this method to the investigation of $B$-meson distribution amplitudes. A very compact form of the distribution amplitudes is obtained. We also investigate the one-loop QCD corrections to the purely leptonic decays of $B$ mesons. We find that, after subtracting the infrared divergence in the one-loop corrections using the factorization method, the QCD one-loop corrections to the leptonic decay amplitude will be zero.
Pion Structure in Qcd: from Theory to Lattice to Experimental Data
Bakulev, A. P.; Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.
We describe the present status of the pion distribution amplitude (DA) as it originates from several sources: (i) a nonperturbative approach based on QCD sum rules with nonlocal condensates, (ii) an O(as) QCD analysis of the CLEO data on Fgg*p(Q2) with asymptotic and renormalon models for higher twists and (iii) recent high-precision lattice QCD calculations of the second moment of the pion DA. We show predictions for the pion electromagnetic form factor, obtained in analytic QCD perturbation theory, and compare it with the JLab data on Fp(Q2). We also discuss in this context an improved model for nonlocal condensates in QCD and show its consequences for the pion DA and the gg*p transition form factor. We include a brief analysis of meson-induced massive lepton (muon) Drell-Yan production for the process p-Nm+m-X, considering both an unpolarized nucleon target and longitudinally polarized protons.
Energy Technology Data Exchange (ETDEWEB)
Devereux, M.J.
1979-05-01
Elastic pion scattering from /sup 9/Be, /sup 28/Si, /sup 58/Ni, and /sup 208/Pb at 162 MeV is analyzed and compared with an optical model theory which incorporates a pion--nucleon range. Excellent fits to the data are obtained in all but one case. The fitted values of the pion--nucleon range, as well as other fitted values are listed. 108 references.
Wilson, Lynn B., III
2010-01-01
We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce or = 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).
Eta Production from Hydrogen using Pion and Kaon Beams.
Tippens, W. Bradford
1999-10-01
Eta meson production data from pions and kaons near threshold are scarce and of poor quality. These data are important for determining the η n and ηΛ scattering lengths and for determining the role of resonances in the η production process. Both processes interestingly have dominant production resonances with masses very near the reaction threshold, which complicates the determination of the resonance parameters. Precision η production data from pions are needed to help resolve ambiguities in the determination of the resonance parameters of the N S_11 resonance and in the determination of the helicity amplitudes for η photoproduction. We report differential cross sections for η production near threshold from the reactions π^- p→ η n and K^- p→ ηΛ based upon data recently taken by the Crystal Ball Collaboration. Excitation functions and angular distributions will be presented. Angular distributions from both reactions show significant deviation from S-wave production.
Pion transition form factor in k_T factorization
Li, Hsiang-nan
2009-01-01
It has been pointed out that the recent BaBar data on the pi gamma^* -> gamma transition form factor F_{pi gamma}(Q^2) at low (high) momentum transfer squared Q^2 indicate an asymptotic (flat) pion distribution amplitude. These seemingly contradictory observations can be reconciled in the k_T factorization theorem: the increase of the measured Q^2F_{pi gamma}(Q^2) for Q^2 > 10 GeV^2 is explained by convoluting a k_T dependent hard kernel with a flat pion distribution amplitude, k_T being a parton transverse momentum. The low Q^2 data are accommodated by including the resummation of alpha_s ln^2x, x being a parton momentum fraction, which provides a stronger suppression at the endpoints of x. The next-to-leading-order correction to the pion transition form factor is found to be less than 20% in the considered range of Q^2.
Pion transition form factor in k{sub T} factorization
Energy Technology Data Exchange (ETDEWEB)
Li, Hsiang-nan [Academica Sinica, Taipei, Taiwan (China). Inst. of Physics; Tsing-Hua Univ., Hsinchu, Taiwan (China). Dept. of Phyiscs; National Cheng-Kung Univ., Tainan, Taiwan (China). Dept. of Physics; National Cheng-Chi Univ, Taipei, Taiwan (China). Inst. of Applied Physics; Mishima, Satoshi [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2009-07-15
It has been pointed out that the recent BaBar data on the {pi}{gamma}{sup *} {yields} {gamma} transition form factor F{sub {pi}}{sub {gamma}}(Q{sup 2}) at low (high) momentum transfer squared Q{sup 2} indicate an asymptotic (flat) pion distribution amplitude. These seemingly contradictory observations can be reconciled in the k{sub T} factorization theorem: the increase of the measured Q{sup 2}FF{sub {pi}}{sub {gamma}}(Q{sup 2}) for Q{sup 2} > 10 GeV{sup 2} is explained by convoluting a k{sub T} dependent hard kernel with a flat pion distribution amplitude, k{sub T} being a parton transverse momentum. The low Q{sup 2} data are accommodated by including the resummation of {alpha}{sub s} ln{sup 2}x, x being a parton momentum fraction, which provides a stronger suppression at the endpoints of x. The next-to-leading-order correction to the pion transition form factor is found to be less than 20% in the considered range of Q{sup 2}. (orig.)
Neutrino-induced coherent pion production
Alvarez-Ruso, L; Hirenzaki, S; Vacas, M J Vicente; Leitner, T; Mosel, U
2007-01-01
We have investigated the neutrino induced coherent pion production reaction at the energies of interest for recent experiments like K2K and MiniBooNE. The model includes pion, nucleon and the Delta(1232) resonance. Medium effects in the production mechanism and the distortion of the pion wave function are taken into account. We find a strong reduction of the cross section due to these effects and also substantial modifications in the energy distributions of the final pion. The sensitivity of the results on the axial N-Delta coupling C5A(0) and the coherent fraction in neutral-current pi0 production are discussed.
An Update on Distribution Amplitudes of the Nucleon and its Parity Partner
Schiel, R W; Braun, V M; Collins, S; Göckeler, M; Hagen, C; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schäfer, A; Schierholz, G; Stüben, H; Wein, P; Zanotti, J M
2011-01-01
The calculation of baryon wave functions at small inter-quark separations is an ongoing effort within the QCDSF collaboration. In this update on normalization constants and distribution amplitudes of the nucleon and its negative parity partner, N* (1535), we present new lattice data which helps us controlling finite size effects. We use new chiral perturbation theory results to perform the extrapolation to the physical point.
Avakian, V. V.; Azarian, M. O.; Egiyan, K. S.; Mamidjanian, E. A.; Ohanian, G. Z.; Ter-Antonian, S. V.
1985-01-01
Based on the analysis of approximates 5 X 1000 events registered on the PION installation, data are obtained on the angular distribution and multiplicity of particles, flying back into the laboratory coordinate system (LCS) that are identified mainly as hadrons produced in the reactions of hFe yield h prime X type. The inclusively produced hadron energy is 200 MeV. The experimental data are compared to the results of the cumulative particle production in hA processes observed on accelerators at lower energies.
Pion Form Factor in QCD at Intermediate Momentum Transfers
Braun, V M; Maul, M
1999-01-01
We present a quantitative analysis of the electromagnetic pion form factor in the light-cone sum rule approach, including radiative corrections and higher-twist effects. The comparison to the existing data favors the asymptotic profile of the pion distribution amplitude and allows to estimate the deviation: $(\\int du/u \\phi_\\pi(u))/ (\\int du/u \\phi^{\\rm as}_\\pi(u))=$ 1.1$\\pm$ 0.1 at the scale 1 GeV. Special attention is payed to the precise definition and interplay of soft and hard contributions at intermediate momentum transfer, and to matching of the sum rule to the perturbative QCD prediction. We observe a strong numerical cancellation between the soft (end point) contribution and power suppressed hard contributions of higher twist, so that the total nonperturbative correction to the usual pQCD result turns out to be of order 30% for $Q^2\\sim 1$ GeV$^2$.
Double pion photoproduction in nuclei
Vicente-Vacas, M J; Gómez-Tejedor, J A; Vicente-Vacas, M J; Oset, E; Gómez Tejedor, J A
1994-01-01
Abstract: The inclusive A(gamma,pi+ pi-)X reaction is studied theoretically. A sizeable enhancement of the cross section is found, in comparison with the scaling of the deuteron cross section (sigma_deuteron * A/2). This enhancement is due to the modifications in the nuclear medium of the gamma N ----> pi pi N amplitude and the pion dispersion relation. The enhancement is found to be bigger than the one already observed in the (pi,pi pi) reaction in nuclei.
Coherent pion production in neutrino-nucleus collisions
Alvarez-Ruso, L; Hirenzaki, S; Vacas, M J Vicente
2007-01-01
We have investigated the neutrino induced coherent pion production reaction at low and intermediate energies including pion, nucleon and Delta(1232) resonance. Medium effects in the production mechanism and the distortion of the pion wave function are included in the calculation. We find a strong reduction of the cross section due to these effects and also substantial modifications in the energy distributions of the final pion. The dependence on the atomic number is discussed.
The photon-pion transition form factor: incompatible data or incompatible models?
de Melo, J P B C; Frederico, T
2013-01-01
The elastic and $\\gamma \\to \\pi$ transition form factors of the pion along with its usual static observables are calculated within a light-front field approach to the constituent quark model. The focus of this exercise in a simple model is on a unified description of all observables with one singly parametrized light-front wave function to detect possible discrepancies in experimental data, in particular the contentious large momentum-squared data on the transition factor as reported by BaBar and Belle. We also discuss the relation of a small to vanishing pion charge radius with an almost constant pion distribution amplitude and compare our results with those obtained in a holographic light-front model.
Energy Technology Data Exchange (ETDEWEB)
Sibirtsev, A; Haidenbauer, J; Huang, F; Krewald, S; Meissner, U -G
2009-04-01
We present a systematic analysis of backward pion photoproduction for the reactions $ \\gamma$ p $ \\rightarrow$ $ \\pi^{0}_{}$ p and $ \\gamma$ p $ \\rightarrow$ $ \\pi^{+}_{}$ n . Regge phenomenology is applied at invariant collision energies above 3GeV in order to fix the reaction amplitude. A comparision with older data on $ \\pi^{0}_{}$ - and $ \\pi^{+}_{}$ -photoproduction at $ \\vartheta$ = 180° indicates that the high-energy limit as given by the Regge calculation could be reached possibly at energies of around $ \\sqrt{{s}}$ ≃ 3 GeV. In the energy region of $ \\sqrt{{s}}$ $ \\le$2.5 GeV, covered by the new measurements of $ \\gamma$ p $ \\rightarrow$ $ \\pi^{0}_{}$ p differential cross-sections at large angles at ELSA, JLab, and LEPS, we see no clear signal for a convergence towards the Regge results. The baryon trajectories obtained in our analysis are in good agreement with those given by the spectrum of excited baryons.
Pion-nucleon scattering inside the Mandelstam triangle
Büttiker, P; Büttiker, Paul; Meissner, Ulf-G.
2000-01-01
We study the third order pion-nucleon scattering amplitude obtained from heavy baryon chiral perturbation theory inside the Mandelstam triangle. We reconstruct the pion-nucleon amplitude in the unphysical region by use of dispersion relations and determine the pertinent low-energy constants by a fit to this amplitude. A detailed comparison with values obtained from phase shift analysis is given. Our analysis leads to a pion-nucleon sigma-term of sigma(0)=40 MeV based on the Karlsruhe partial wave analysis. We have repeated the same procedure using the latest solution of the VPI group and find a much larger value for sigma(0).
Double Pion Production Reactions
Oset, E; Cano, F; Hernández, E; Kamalov, S S; Nacher, J C; Tejedor, J A G
1999-01-01
We report on reactions producing two pions induced by real and virtual photons or nucleons. The role of different resonances in these reactions is emphasized. Novel results on coherent two pion photoproduction in nuclei are also reported.
Pire, Bernard; Szymanowski, Lech
2010-01-01
We construct a spectral representation for the transition distribution amplitudes (TDAs), i.e. matrix elements of three quark correlators which arise e.g. in the description of baryon to meson and baryon to photon transitions within the factorization approach to hard exclusive reactions. We generalize for these quantities the notion of double distributions introduced in the context of generalized parton distributions. We propose the generalization of A.Radyushkin's factorized Ansatz for the case of baryon to meson and baryon to photon TDAs. Our construction opens the way to modeling of baryon to meson and baryon to photon TDAs in their complete domain of definition and quantitative estimates of cross-sections for various hard exclusive reactions.
Pion structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Javadi Motaghi, Narjes
2015-05-12
In this thesis we use lattice QCD to compute the second Mellin moments of pion generalized parton distributions and pion electromagnetic form factors. For our calculations we are able to analyze a large set of gauge configurations with 2 dynamical flavours using non-perturbatively the improved Wilson-Sheikholeslami-Wohlert fermionic action pion masses ranging down to 151 MeV. By employing improved smearing we were able to suppress excited state contamination. However, our data in the physical quark mass limit show that some excited state contamination remains. We show the non-zero sink momentum is optimal for the computation of the electromagnetic form factors and generalized form factors at finite momenta.
Pion transition form factor through Dyson-Schwinger equations
Raya, Khépani
2016-01-01
In the framework of Dyson-Schwinger equations (DSE), we compute the $\\gamma^*\\gamma\\to\\pi^0$ transition form factor, $G(Q^2)$. For the first time, in a continuum approach to quantun chromodynamics (QCD), it was possible to compute $G(Q^2)$ on the whole domain of space-like momenta. Our result agrees with CELLO, CLEO and Belle collaborations and, with the well-known asymptotic QCD limit, $2f_\\pi$. Our analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor.
Pion transition form factor through Dyson-Schwinger equations
Raya, Khépani
2016-10-01
In the framework of Dyson-Schwinger equations (DSE), we compute the γ*γ→π0 transition form factor, G(Q2). For the first time, in a continuum approach to quantun chromodynamics (QCD), it was possible to compute G(Q2) on the whole domain of space-like momenta. Our result agrees with CELLO, CLEO and Belle collaborations and, with the well- known asymptotic QCD limit, 2ƒπ. Our analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor.
Low Energy Pion-Pion Elastic Scattering in Sakai-Sugimoto Model
Parthasarathy, R
2008-01-01
We have considered the holographic large $N_c$ QCD model proposed by Sakai and Sugimoto and evaluated the non-Abelian DBI-action on the D8-brane upto $(\\alpha')^4$ terms. Restricting to the pion sector, these corrections give rise to four derivative contact terms for the pion field. We derive the Weinberg's phenemenological lagrangian. The coefficients of the four derivative terms are determined in terms of $g_{YM}^2$. The low energy pion-pion scattering amplitudes are evaluated. Numerical results are presented with the choice of $M_{KK}=0.94 GeV$ and $N_c=11$. The results are compared with the amplitudes calculated using the experimental phase shifts. The agreement with the experimental data is found to be satisfactory.
Quark-Hadron Duality for the Pion: a Phenomenological Study
Energy Technology Data Exchange (ETDEWEB)
Wally Melnitchouk
2002-08-01
We explore the relationship between exclusive and inclusive electromagnetic scattering from the pion, focusing on the transition region at intermediate Q{sup 2}. Combining Drell-Yan data on the leading twist quark distribution in the pion with a model for the resonance region at large x, we calculate QCD moments of the pion structure function over a range of Q{sup 2}, and quantify the role of higher twist corrections. Using a parameterization of the pion elastic form factor and phenomenological models for the pi --> p transition form factor, we test the extent to which local duality may be valid for the pion.
Directory of Open Access Journals (Sweden)
Ding Minghui
2016-01-01
Full Text Available We compute the valence-quark leading twist parton distribution amplitudes (PDAs of heavy pseudoscalar mesons ηc and ηb and find that they are both broader than the δ-like function while narrower than the asymptotic one. The evolution of distribution amplitude with momentum scale is then considered and PDAs will turn to a asymptotic form when the momentum goes to infinity.
Ebels, Ursula; Buda, Liliana D.; Ounadjela, Kamel; Wigen, Phillip E.
The general purpose of this review is to introduce to the dynamics of small amplitude excitations of nonhomogeneous magnetization distributions. This is in contrast to the dynamics of the magnetization reversal process, which corresponds to large amplitude perturbations, discussed in other contributions of this book. Small amplitude oscillations can be studied by ferromagnetic resonance or Brillouin light scattering. The latter technique isused to investigate the excitation spectrum in laterally constrained structures.This review introduces ferromagnetic resonance and focuses on the role of the pumping field orientation. Upon varying the pumping field orientation, fundamental modes can be selectively excited, giving, in particular, access to regions of varying magnetic orientation. This is demonstrated for the excitation spectrum of magnetic domains and domain walls of the stripe domain structure in metallic thin films. These stripe domains can be considered laterally constrained magnetic units 40-100 nm wide, separated by domain walls.Such experiments provide information on the domain and domain wall structure and in principle yield the internal fields and the coupling fields of the domains, as well as the wall mass and the stabilizing forces of the domain walls. The wall mass itself is a dynamic parameter which intervenes upon wall acceleration but is of less importance when considering steady-state wall propagation in the magnetization reversal process. However, the wall mass depends sensitively on the spin configuration inside the wall, and therefore resonance experiments can provide insight into the structure of the domain wall. The wall structure, on the other hand, plays an important role in spin-polarized transport experiments, investigating the contribution of a domain wall to the resistance [1] or the transfer of momentum from the conduction electrons to the wall [2,3].
Inelastic pion scattering by /sup 13/C at low energies
Energy Technology Data Exchange (ETDEWEB)
Mitchell, J.H.
1987-03-01
Angular distributions for inelastically scattered pions were obtained for several states in /sup 13/C at an incident energy of 65 MeV. The data include results from both ..pi../sup +/ and ..pi../sup -/ measurements. In addition, ..pi../sup -/ measurements were made at T/sub ..pi../ = 50 MeV at one angle to give a two point fixed-q excitation function. The data are compared to theory and the data of others. As might be expected, medium corrections are shown to be considerably more important at low energies than at resonance. This is true for inelastic transitions of multipolarity 0,2 and 3. Parameters derived from an analysis of elastic pion scattering and SCX data also provide an adequate description of the inelastic transitions. The charge asymmetry in the cross sections for the 9/2/sup +/ state that was seen at resonance persists at these energies. This result is consistent with an impulse approximation treatment of the spin-flip amplitude. This is true even though the incoming energy of the pions is far below the range where the validity of an impulse treatment is expected. 65 refs., 45 figs.
Charged current neutrino induced coherent pion production
Alvarez-Ruso, L; Hirenzaki, S; Vacas, M J V
2007-01-01
We analyze the neutrino induced charged current coherent pion production at the energies of interest for recent experiments like K2K and MiniBooNE. Medium effects in the production mechanism and the distortion of the pion wave function, obtained solving the Klein Gordon equation with a microscopic optical potential, are included in the calculation. We find a strong reduction of the cross section due to these effects and also substantial modifications of the energy distributions of the final lepton and pion.
Fu, Hai-Bing; Cheng, Wei; Zhong, Tao
2016-01-01
We revisit the $\\rho$-meson longitudinal leading-twist distribution amplitude (DA) $\\phi_{2;\\rho}^\\|$ by using the QCD sum rules approach within the background field theory. To improve the accuracy of the sum rules for its moments $\\langle\\xi_{n;\\rho}^\\|\\rangle$, we include the next-to-leading order QCD correction to the perturbative part and keep all non-perturbative condensates up to dimension-six consistently within the background field theory. The first two moments read $\\langle \\xi_{2;\\rho}^\\| \\rangle|_{1{\\rm GeV}} = 0.241(28)$ and $\\langle \\xi_{4;\\rho}^\\| \\rangle|_{1{\\rm GeV}} = 0.108(27)$, indicating a double humped behavior for $\\phi_{2;\\rho}^\\|$ at low $q^2$-region. As an application, we apply them to the $B\\to \\rho $ transition form factors within the QCD light-cone sum rules, which are key components for the decay width $\\Gamma(B\\to \\rho \\ell \
Double pion photoproduction in nuclei
Energy Technology Data Exchange (ETDEWEB)
Gomez Tejedor, J.A. [Departamento de Fisica Teorica, Valencia (Spain); Vicente-Vacas, M.J. [Departamento de Fisica Teorica, Valencia (Spain); Oset, E. [Departamento de Fisica Teorica, Valencia (Spain)
1995-06-19
The inclusive A({gamma},{pi}{sup +}{pi}{sup -})X reaction is studied theoretically. A sizable enhancement of the cross section is found, in comparison with the scaling of the deuteron cross section ({sigma}{sub d} A/2). This enhancement is due to the modifications in the nuclear medium of the {gamma}N {yields}{pi}{pi}N amplitude and the pion dispersion relation. The enhancement is found to be bigger than the one already observed in the ({pi},{pi}{pi}) reaction in nuclei. ((orig.)).
Low Energy Pion-Hyperon Interaction
Hama, Y
2001-01-01
We study the low energy pion-hyperon interaction considering effective non-linear chiral invariant Lagrangians including pions, rho mesons, hyperons and corresponding resonances. Then we calculate the S- and P-wave phase-shifts, total cross sections, angular distributions and polarizations for the momentum in the center-of-mass frame up to k=400 MeV. With these results we discuss the CP violation in the csi-> pi-lambda and omega-> pi-csi weak decays.
Imaging dynamical chiral-symmetry breaking: pion wave function on the light front.
Chang, Lei; Cloët, I C; Cobos-Martinez, J J; Roberts, C D; Schmidt, S M; Tandy, P C
2013-03-29
We project onto the light front the pion's Poincaré-covariant Bethe-Salpeter wave function obtained using two different approximations to the kernels of quantum chromodynamics' Dyson-Schwinger equations. At an hadronic scale, both computed results are concave and significantly broader than the asymptotic distribution amplitude, φ(π)(asy)(x)=6x(1-x); e.g., the integral of φ(π)(x)/φ(π)(asy)(x) is 1.8 using the simplest kernel and 1.5 with the more sophisticated kernel. Independent of the kernels, the emergent phenomenon of dynamical chiral-symmetry breaking is responsible for hardening the amplitude.
Medium Effects of Low Energy Pions
Friedman, E.
2004-03-01
Fits of pion--nucleus potentials to large sets of pionic atom data reveal departures of parameter values from the corresponding free π N parameters. These medium effects can be quantitatively reproduced by a chiral-motivated model where the pion decay constant is modified in the medium or by including the empirical on-shell energy dependence of the amplitudes. No consistency is obtained between pionic atoms and the free π N interaction when an extreme off-shell chiral model is used. The role of the size of data sets is briefly discussed.
DSE inspired model for the pion's valence dressed-quark GPD
Chang, L; Moutarde, H; Roberts, C D; Rodríguez-Quintero, J; Sabatié, F
2015-01-01
We sketch here an approach to the computation of generalised parton distributions (GPDs), based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD, $H_\\pi^{\\rm v}(x,\\xi,t)$. Our analysis focuses on the case of zero skewness, $\\xi=0$, and underlines that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for $H_\\pi^{\\rm v}(x,0,t)$, expressed as the Radon transform of a single amplitude. Therewith we obtain results for $H_\\pi^{\\rm v}(x,0,t)$ and the associated impact-parameter dependent distribution, $q_\\pi^{\\rm v}(x,|\\vec{b}_\\perp|)$, which provide a qualitatively sound picture of the pion's dressed-quark structure at an hadronic scale.
Study of the Two-pion Photoproduction on the Deuteron
Energy Technology Data Exchange (ETDEWEB)
Graham, Lewis P. [Univ. of South Carolina, Columbia, SC (United States)
2012-12-01
Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the primary challenges in strong interaction physics. This interaction is governed by Quantum Chromodynamics (QCD), which is a theory for understanding the dynamics of strong. QCD displays the asymptotic freedom of hadrons at very short distances and also the confinement of quarks and gluons inside hadrons. However, solutions of this QCD theory in the non-perturbative domain of the interaction are extremely difficult to achieve, mainly because confinement happens on the hadronic scale on which the coupling constant is large and prevents any perturbative approach. Thus leaving us with strategies such as lattice QCD or formulating QCD sum rules to get around this problem. In exclusive hadron production the yN interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be investigated through the transition amplitudes to the N and Delta resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through meson photoproduction. To gain more detailed insight into this interaction, we look to probe the baryon structure of the nucleon and the photo-excited resonance decays through photon scattering off a deuteron producing two pions in the final state. This photoproduction process off the deuteron will be used to investigate known baryon resonances in the two pion channel. The two pion final state will be investigated for unraveling new information into the photo-coupling strengths. We want to explore final state interactions, search for properties of known resonances, and to explore the possibility of seeing missing states that are predicted by quark models but have not yet been found experimentally. Using the CEBAF Large
Evolution equation for B-meson distribution amplitude in HQET in the coordinate space
Kawamura, Hiroyuki
2010-01-01
The B-meson distribution amplitude (DA) is defined as the matrix element of a quark-antiquark bilocal light-cone operator in the heavy-quark effective theory, corresponding to a long-distance component in the factorization formula for exclusive B-meson decays. The evolution equation for the B-meson DA is governed by the cusp anomalous dimension as well as the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-type anomalous dimension, and these anomalous dimensions give the "quasilocal" kernel in the coordinate-space representation. We show that this evolution equation can be solved analytically in the coordinate-space, accomplishing the relevant Sudakov resummation at the next-to-leading logarithmic accuracy. The quasilocal nature leads to a quite simple form of our solution which determines the B-meson DA with a quark-antiquark light-cone separation $t$ in terms of the DA at a lower renormalization scale $\\mu$ with smaller interquark separations $zt$ ($z \\leq 1$). This formula allows us to present rigorous calculat...
Heavy Pseudoscalar Twist-3 Distribution Amplitudes within QCD Theory in Background Fields
Zhong, Tao; Huang, Tao; Fu, Hai-Bing
2016-01-01
In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudo-scalars such as $\\eta_c$, $B_c$ and $\\eta_b$. New sum rules for the twist-3 DA moments $\\left_{\\rm HP}$ and $\\left_{\\rm HP}$ up to sixth orders and up to dimension-six condensates are deduced under the framework of the background field theory. Based on the sum rules for the twist-3 DA moments, we construct a new model for the two twist-3 DAs of the heavy pseudo-scalar with the help of the Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the $B_c\\to\\eta_c$ transition form factor ($f^{B_c\\to\\eta_c}_+(q^2)$) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs $\\phi^P_{3;\\eta_c}$ and $\\phi^\\sigma_{3;\\eta_c}$ are important for a reliable prediction of $f^{B_c\\to\\eta_c}_+(q^2)$. For example, at the maximum recoil region, we have $f^{B_c\\to\\eta_c}_+(0) = 0.674 \\pm 0.066$, in which those two twist-3 terms provide $\\sim3...
Leading-twist distribution amplitudes of scalar- and vector-mesons
Li, Bo-Lin; Ding, Minghui; Roberts, Craig D; Zong, Hong-Shi
2016-01-01
A symmetry-preserving truncation of the two-body light-quark bound-state problem in relativistic quantum field theory is used to calculate the leading-twist parton distribution amplitudes (PDAs) of scalar systems, both ground-state and radial excitations, and the radial excitations of vector mesons. Owing to the fact that the scale-independent leptonic decay constant of a scalar meson constituted from equal-mass valence-constituents vanishes, it is found that the PDA of a given scalar system possesses one more zero than that of an analogous vector meson. Consequently, whereas the mean light-front relative momentum of the valence-constituents within a vector meson is zero, that within a scalar meson is large, an outcome which hints at a greater role for light-front angular momentum in systems classified as $P$-wave in quantum mechanical models. Values for the scale-dependent decay constants of ground-state scalar and vector systems are a by-product of this analysis, and they turn out to be roughly equal, viz. ...
Heavy pseudoscalar twist-3 distribution amplitudes within QCD theory in background fields
Zhong, Tao; Wu, Xing-Gang; Huang, Tao; Fu, Hai-Bing
2016-09-01
In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudoscalars such as η _c, B_c, and η _b. New sum rules for the twist-3 DA moments Huang-Lepage prescription. Furthermore, we apply them to the B_c→ η _c transition form factor (f^{B_c→ η _c}_+(q^2)) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs φ ^P_{3;η _c} and φ ^σ _{3;η _c} are important for a reliable prediction of f^{B_c→ η _c}_+(q^2). For example, at the maximum recoil region, we have f^{B_c→ η _c}_+(0) = 0.674 ± 0.066, in which those two twist-3 terms provide {˜ }33 and {˜ }22 % contributions. Also we calculate the branching ratio of the semi-leptonic decay B_c → η _c lν as Br(B_c → η _c lν ) = ( 9.31^{+2.27}_{-2.01} ) × 10^{-3}.
ρ -meson longitudinal leading-twist distribution amplitude within QCD background field theory
Fu, Hai-Bing; Wu, Xing-Gang; Cheng, Wei; Zhong, Tao
2016-10-01
We revisit the ρ -meson longitudinal leading-twist distribution amplitude (DA) ϕ2;ρ ∥ by using the QCD sum rules approach within the background field theory. To improve the accuracy of the sum rules for its moments ⟨ξn;ρ ∥⟩ , we include the next-to-leading order QCD correction to the perturbative part and keep all nonperturbative condensates up to dimension-six consistently within the background field theory. The first two moments read ⟨ξ2;ρ ∥⟩|1 GeV=0.241 (28 ) and ⟨ξ4;ρ ∥⟩|1 GeV=0.109 (10 ) , indicating a double humped behavior for ϕ2;ρ ∥ at small energy scale. As an application, we apply them to the B →ρ transition form factors within the QCD light-cone sum rules, which are key components for the decay width Γ (B →ρ ℓνℓ) . To compare with the world average of Γ (B →ρ ℓνℓ) issued by Particle Data Group, we predict |Vub|=3.1 9-0.62+0.65 , which agrees with the BABAR and Omnès parametrization prediction within errors.
Leading-twist parton distribution amplitudes of S-wave heavy-quarkonia
Directory of Open Access Journals (Sweden)
Minghui Ding
2016-02-01
Full Text Available The leading-twist parton distribution amplitudes (PDAs of ground-state S01 and S13 cc¯- and bb¯-quarkonia are calculated using a symmetry-preserving continuum treatment of the meson bound-state problem which unifies the properties of these heavy-quark systems with those of light-quark bound-states, including QCD's Goldstone modes. Analysing the evolution of S01 and S13 PDAs with current-quark mass, mˆq, increasing away from the chiral limit, it is found that in all cases there is a value of mˆq for which the PDA matches the asymptotic form appropriate to QCD's conformal limit and hence is insensitive to changes in renormalisation scale, ζ. This mass lies just above that associated with the s-quark. At current-quark masses associated with heavy-quarkonia, on the other hand, the PDAs are piecewise convex–concave–convex. They are much narrower than the asymptotic distribution on a large domain of ζ; but nonetheless deviate noticeably from φQQ¯(x=δ(x−1/2, which is the result in the static-quark limit. There are also material differences between S01 and S13 PDAs, and between the PDAs for different vector-meson polarisations, which vanish slowly with increasing ζ. An analysis of moments of the root-mean-square relative-velocity, 〈v2m〉, in S01 and S13 systems reveals that 〈v4〉-contributions may be needed in order to obtain a reliable estimate of matrix elements using such an expansion, especially for processes involving heavy pseudoscalar quarkonia.
Feinberg, I; Thode, H C; Chugani, H T; March, J D
1990-01-23
We analyzed the available ontogenetic data (birth to 30 years of age) for: amplitude of delta EEG (DA) waves during sleep; cortical metabolic rate (CMR) measured with positron emission tomography; and synaptic density (SD) in frontal cortex. Each is at the adult level at birth, increases to about twice this level by 3 years of age, and then gradually falls back to the adult level over the next two decades. Statistical analyses revealed that individual gamma distribution models fit each data set as well as did the best ad hoc polynomial. A test of whether a single gamma distribution model could describe all three data sets gave good results for DA and CMR but the fit was unsatisfactory for SD. However, because so few data were available for SD, this test was not conclusive. We proposed the following model to account for these changes. First, cortical neurons are stimulated by birth to enter a proliferative state (PS) that creates many connections. Next, as a result of interactions in the PS, neurons are triggered into a transient organizational state (OS) in which they make enduring connections. The OS has a finite duration (minutes to years), and is characterized by high rates of information-processing and metabolism. Levels of CMR, SD and DA, therefore, are proportional to the number of neurons in the OS at any time. Thus, the cortex after birth duplicates, over a vastly greater time scale, the overproduction and regression of neural elements that occurs repeatedly in embryonic development. Finally, we discussed the implications of post-natal brain changes for normal and abnormal brain function. Mental disorders that have their onset after puberty (notably schizophrenia and manic-depressive psychoses) might be caused by errors in these late maturational processes. In addition to age of onset, this neurodevelopmental hypothesis might explain several other puzzling features of these subtle disorders.
Exclusive channels in semi-inclusive production of pions and kaons
Energy Technology Data Exchange (ETDEWEB)
Markus Diehl; Wolfgang Kugler; Andreas Schaefer; Christian Weiss
2005-06-01
We investigate the role of exclusive channels in semi-inclusive electroproduction of pions and kaons. Using the QCD factorization theorem for hard exclusive processes we evaluate the cross sections for exclusive pseudoscalar and vector meson production in terms of generalized parton distributions and meson distribution amplitudes. We investigate the uncertainties arising from the modeling of the nonperturbative input quantities. Combining these results with available experimental data, we compare the cross sections for exclusive channels to that obtained from quark fragmentation in semi-inclusive deep inelastic scattering. We find that rho0 production is the only exclusive channel with significant contributions to semi-inclusive pion production at large z and moderate Q2. The corresponding contribution to kaon production from the decay of exclusively produced phi and Kstar is rather small.
Parameters of Fermi-motion from Quasielastic Backward Pion-Proton Scattering on Nuclei
Abramov, B M; Dukhovskoy, I A; Khanov, A I; Krestnikov, Yu S; Krutenkova, A P; Kulikov, V V; Matsuk, M A; Radkevich, I A; Turdakina, E N
1999-01-01
In experiment on the study of the quasielastic pion-proton scattering at large momentum transfer on nuclei the proton Fermi-momentum distributions have been analysed in plane-wave approximation for light nuclei $^6$Li, $^7$Li and $^{12}$C. It was found that, contrary to (e,e') experiments, that the oscillator model gives slightly better description of our data than the Fermi - gas model. But the values of parameters of the distributions obtained in our analysis are considerably smaller, than in (e,e') experiments. It gives evidence that the plane-wave approximation is not sufficient and more complicated theoretical models which take into account the effects of distortion of pion-nucleon amplitude in a nuclear medium are necessary for analysis of our data.
Lansberg, J P; Szymanowski, L
2007-01-01
We evaluate the cross section for anti-p p -> l+ l- pi0 in the forward direction and for large lepton pair invariant mass. In this kinematical region, the leading-twist amplitude factorises into a short-distance matrix element, long-distance dominated antiproton Distribution Amplitudes and proton to pion Transition Distribution Amplitudes (TDA). Using a modelling inspired from the chiral limit for these TDAs, we obtain a first estimate of this cross section, thus demonstrating that this process can be measured at GSI-FAIR.
Heavy pseudoscalar twist-3 distribution amplitudes within QCD theory in background fields
Energy Technology Data Exchange (ETDEWEB)
Zhong, Tao [Henan Normal University, College of Physics and Materials Science, Xinxiang (China); Wu, Xing-Gang [Chongqing University, Department of Physics, Chongqing (China); Huang, Tao [Chinese Academy of Sciences, Institute of High Energy Physics and Theoretical Physics Center for Science Facilities, Beijing (China); Fu, Hai-Bing [Guizhou Minzu University, School of Science, Guiyang (China)
2016-09-15
In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudoscalars such as η{sub c}, B{sub c}, and η{sub b}. New sum rules for the twist-3 DA moments left angle ξ{sup n}{sub P} right angle {sub HP} and left angle ξ{sup n}{sub σ} right angle {sub HP} up to sixth order and up to dimension-six condensates are deduced under the framework of the background field theory. Based on the sum rules for the twist-3 DA moments, we construct a new model for the two twist-3 DAs of the heavy pseudoscalar with the help of the Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the B{sub c} → η{sub c} transition form factor (f{sub +}{sup B{sub c}→η{sub c}}(q{sup 2})) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs φ{sup P}{sub 3;η{sub c}} and φ{sup σ}{sub 3;η{sub c}} are important for a reliable prediction of f{sub +}{sup B{sub c}→η{sub c}}(q{sup 2}). For example, at the maximum recoil region, we have f{sub +}{sup B{sub c}→η{sub c}}(0) = 0.674 ± 0.066, in which those two twist-3 terms provide ∝33 and ∝22% contributions. Also we calculate the branching ratio of the semi-leptonic decay B{sub c} → η{sub c}lν Br(B{sub c} → η{sub c}lν) = (9.31{sup +2.27}{sub -2.01}) x 10{sup -3}. (orig.)
Pion Form Factor in Chiral Limit of Hard-Wall AdS/QCD Model
Energy Technology Data Exchange (ETDEWEB)
Anatoly Radyushkin; Hovhannes Grigoryan
2007-12-01
We develop a formalism to calculate form factor and charge density distribution of pion in the chiral limit using the holographic dual model of QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and present analytic expressions for these functions and for the pion form factor. They allow to relate such observables as the pion decay constant and the pion charge electric radius to the values of chiral condensate and hard-wall cutoff scale. The evolution of the pion form factor to large values of the momentum transfer is discussed, and results are compared to existing experimental data.
Li, Xiaoyan; Fisher, Morris; Rymer, William Zev; Zhou, Ping
2016-06-01
The F-response was used in this study to assess changes in the first dorsal interosseous (FDI) muscle after a hemispheric stroke. The number of motor units and their sizes were estimated bilaterally in 12 stroke survivors by recording both the compound muscle action potential (CMAP) and F wave responses. These F waves were induced by applying a large number of electrical stimuli to the ulnar nerve. The amplitude distribution of individual motor unit action potentials (MUAPs) was also compared between paretic and contralateral muscles. When averaged across all the subjects, a significantly lower motor unit number estimate was obtained for the paretic FDI muscle ( 88 ±13) compared with the contralateral side ( 139 ±11) ( ). Pooled surface MUAP amplitude analysis demonstrated a right-skewed distribution for both paretic (kurtosis 3.0) and contralateral (kurtosis 8.52) muscles. When normalized to each individual muscle's CMAP, the surface MUAP amplitude ranged from 0.22% to 4.94% (median 1.17%) of CMAP amplitude for the paretic muscle, and from 0.13% to 3.2% (median 0.62%) of CMAP amplitude for the contralateral muscle. A significant difference in MUAP outliers was also observed between the paretic and contralateral muscles. The findings of this study suggest significant motor unit loss and muscle structural reorganization after stroke.
Two-pion interferometry for a partially coherent evolution source
Institute of Scientific and Technical Information of China (English)
LI Jian-Wei; YU Li-Li; ZHANG Wei-Ning
2008-01-01
We give the formulas of two-pion Hanbury-Brown-Twiss (HBT) correlation function for a partially coherent evolution pion-emitting source,using quantum probability amplitudes in a path-integral formalism.The multiple scattering of the particles in the source is taken into consideration based on Glauber scattering theory.Two-pion interferometry with effects of the multiple scattering and source collective expansion is examined for a partially coherent source of hadronic gas with a finite baryon density and evolving hydrodynamically.We do not find observable effect of either the multiple scattering or the source collective expansion on HBT chaotic parameter.
Dropping Sigma-Meson Mass and In-Medium S-Wave pion-pion Correlations
Aouissat, Z; Schuck, P; Wambach, J
1999-01-01
The influence of a dropping sigma-meson mass on previously calculated in-medium pion-pion correlations in the J=I=0 (sigma-meson) channel is investigated. It is found that the invariant-mass distribution around the vacuum threshold experiences a further strong enhancement with respect to standard many-body effects. The relevance of this result for the explanation of recent $A(\\pi,2\\pi)X$ data is pointed out.
Measurements of pion-helium total cross sections at energies from 51 to 105 MeV
Energy Technology Data Exchange (ETDEWEB)
Johnson, K.F.
1976-10-01
Measurements of ..pi../sup + -/-/sup 4/He total cross sections have been made at energies from 51 to 105 MeV using a superfluid /sup 4/He target at the Low Energy Pion channel of the LAMPF accelerator in Los Alamos. Pions were selected with either a DISC counter or a time-of-flight system. The scattered pions were detected by a series of circular plastic scintillation counters using standard transmission techniques. The resulting partial removal cross sections were extrapolated to zero solid angle after being corrected for Coulomb effects, pion decay, accidental counts, counter absorption and efficiencies, and statistical correlations. The resulting statistical errors were generally approximately 3-5 percent. The measured total cross sections were found to be in good statistical agreement with previous measurements and in poor agreement with the predictions of several optical potentials in current use. Through an optical theorem the imaginary part of the forward scattering amplitude was found. The total cross sections have been used with previously-measured angular distributions through a phenomenological model to obtain the real part of the forward scattering amplitude at four energies between 50 and 75 MeV. These results were found to be in good agreement with forward dispersion relation calculations.
Bietenholz, W; Horsley, R; Nakamura, Y; Pleiter, D; Rakow, P E L; Schierholz, G; Zanotti, J M
2010-01-01
The residual mass of the pion in a finite spatial box at vanishing quark masses is computed with two flavors of dynamical clover fermions. The result is compared with predictions of chiral perturbation theory in the delta regime.
Pion absorption on 3He at low energies
Hahn, H.; Altman, A.; Ashery, D.; Gefen, G.; Gill, D. R.; Johnson, R. R.; Levy-Nathansohn, R.; Moinester, M. A.; Sevior, M.; Trelle, R. P.
1996-03-01
The reactions 3He(π+,pp)p and 3He(π-,pn)n were studied at 37.0 MeV by coincidence detection of two nucleons. The differential cross sections were separated to two-nucleon (σ2N), three-nucleon (σ3N), and final-state interaction (σFSI) components. For π+, the σ2N angular distribution is symmetric about 90°, and the total cross section is 1.5 times the cross section measured for d(π+,pp). For π-, the angular distribution is asymmetric (backward peaked). The asymmetry increases with decreasing energy, indicating increasing pion s-wave contribution at lower energies. The fraction of the cross section induced by s-wave pions as calculated by a partial wave amplitude analysis is 13%. The measured total cross sections are σ2N(π-)=0.85+/-0.08 mb and σ2N(π+)=7.9+/-0.5 mb; σ3N(π-)=1.6+/-0.7 mb and σ3N(π+)=1.3+/-0.3 mb. A new evaluation of σ3N at Tπ=62.5 and 82.8 MeV is given, using data from an earlier experiment. The cross sections leading to the two-nucleon final-state interaction at Tπ=37.0 MeV are also estimated.
Some remarks on pion condensation in relativistic heavy ion collisions
Greiner, C; Müller, B
1993-01-01
Recently it was pointed out that coherent or condensated states of pions may account for the explanation of the Centauro events observed in cosmic ray showers. We argue that an occurrence of condensed pions requires that the system evolves far out of thermal equilibrium. Besides an unusual charge ratio distribution we show that such a produced state also would lead to strong isospin correlations.
Application of a Regge model to the photoproduction of pion pairs
Energy Technology Data Exchange (ETDEWEB)
Bolz, Arthur; Sauter, Michel; Schoening, Andre [Physikalisches Institut, Universitaet Heidelberg, Im Neuenheimer Feld 226, D-69120 Heidelberg (Germany); Ewerz, Carlo [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany); ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt (Germany); Maniatis, Markos [Departamento de Ciencias Basicas, Universidad del Bio-Bio, Avda. Andres Bello s/n, Casilla 447, Chillan 3780000 (Chile); Nachtmann, Otto [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)
2015-07-01
In a recent publication (arXiv:1409.8483) a model in the spirit of Regge theory is used to describe the reaction γp → π{sup +}π{sup -} p at high energies. Both resonant pion-pion production via the meson resonances ρ(770), ω(782), ρ(1450) and f{sub 2}(1270) as well as non-resonant amplitudes are considered. Photon and proton interact by the exchange of the photon, the pomeron and reggeons as well as by a yet unobserved but possible odderon. Cross sections calculated from this model and their dependencies on various kinematic quantities are discussed and compared to experimental data. The focus is on angular distributions which feature asymmetries that could be used for an odderon discovery.
Density and expansion effects on pion spectra in relativistic heavy-ion collisions
Ayala, A P; Montaño-Zetina, L M; Ayala, Alejandro; Barreiro, Julio; Montano, Luis M.
1999-01-01
We compute the pion inclusive momentum distribution in heavy-ion collisions at AGS energies, assuming thermal equilibrium and accounting for density and expansion effects at the time of decoupling. We compare to data on mid rapidity charged pions produced in central Au + Au collisions and find a very good agreement. The shape of the distribution at low m_t-m is explained in part as an effect arising from the high mean pion density achieved in these reactions. The difference between the positive and negative pion distributions in the same region is attributed in part to the different average yields of each kind of charged pions.
Extracting amplitudes from photoproduction data
Workman, R. L.
2011-09-01
We consider the problems associated with amplitude extraction, from meson photoproduction data, over the first resonance regions. The notion of a complete experiment has motivated the FROST program at Jefferson Lab. Exercises applied to pion photoproduction data illustrate the problems to be confronted in any attempt to extract underlying resonance signals from these data (without introducing a model for the resonant process).
Descotes-Genon, S
2003-01-01
We study the radiative decay B -> gamma l nu_l in the framework of QCD factorization. We demonstrate explicitly that, in the heavy-quark limit and at one-loop order in perturbation theory, the amplitude does factorize, i.e. that it can be written as a convolution of a perturbatively calculable hard-scattering amplitude with the (non-perturbative) light-cone distribution amplitude of the B-meson. We evaluate the hard-scattering amplitude at one-loop order and verify that the large logarithms are those expected from a study of the b->u transition in the Soft-Collinear Effective Theory. Assuming that this is also the case at higher orders, we resum the large logarithms and perform an exploratory phenomenological analysis. The questions addressed in this study are also relevant for the applications of the QCD factorization formalism to two-body non-leptonic B-decays, in particular to the component of the amplitude arising from hard spectator interactions.
Pion production and absorption in relativistic nucleus-nucleus collisions
Energy Technology Data Exchange (ETDEWEB)
Senger, P. [GSI Planckstr.1, Darmstadt (Germany)
1993-12-31
In a relativistic nucleus-nucleus collision the projectile kinetic energy is not only converted into thermal and compressional energy of the nucleonic system, but also into internal excitation energy of the nucleons. At bombarding energies around 1 GeV/nucleon a substantial amount of baryonic resonances is produced which decay predominantly into pions. Thus the pion multiplicity, momentum and angular distributions provide information on the space time dynamics of the nuclear reaction system. In this paper the authors report on experiments which try to measure the `primordial` delta or pion abundancy. The idea is to compare the pion yields measured in a heavy and a light system: in the first case pion final-state interactions should happen much more frequently than in the second case. Both inclusive pion cross sections and pion multiplicities per participant nucleon are measured. In addition the authors study the pion emission pattern with respect to the reaction plane to sort out pions which are less affected by absorption and rescattering even in a heavy collision system.
Transverse mass distributions of neutral pions from 208Pb-induced reactions at 158 A GeV
Aggarwal, M.M.; Agnihotri, A.; Ahammed, Z.A.; Angelis, A.L.S.; Antonenko, V.; Arefiev, V.; Astakhov, V.; Avdeitchikov, V.; Awes, T.C.; Baba, P.V.K.S.; Badyal, S.K.; Barlag, C.; Bathe, S.; Batiounia, B.; Bernier, T.; Bhalla, K.B.; Bhatia, V.S.; Blume, C.; Bock, R.; Bohne, E.-M.; Böröcz, Z.K.; Bucher, D.; Buijs, A.; Büsching, H.; Carlén, L.; Chalyshev, V.; Chattopadhyay, S.; Cherbatchev, R.; Chujo, T.; Claussen, A.; Das, A.C.; Decowski, M.P.; Delagrange, H.; Djordjadze, V.; Donni, P.; Doubovik, I.; Dubey, A.K.; Dutt, S.; Dutta Majumdar, M.R.; El Chenawi, K.; Eliseev, S.; Enosawa, K.; Foka, P.; Fokin, S.; Ganti, M.S.; Garpmann, S.; Gavrishchuk, O.; Geurts, F.; Ghosh, T.K.; Glasow, R.; Gupta, S.K.; Guskov, B.; Gustafsson, H.-A.; Gutbrod, H.H.; Higuchi, R.; Hrivnacova, I.; Ippolitov, M.; Kalechofsky, H.; Kamermans, R.; Kampert, K.-H.; Karadjev, K.; Karpio, K.; Kato, S.; Kees, S.; Klein-Bösing, C.; Knoche, S.; Kolb, B.; Kosarev, I.; Koutcheryaev, I.; Krümpel, T.; Kugler, A.; Kulinich, P.; Kurata, M.; Kurita, K.; Kuzmin, N.; Langbein, I.; Bevedev, A.; Lee, Y.Y.; Löhner, H.; Luquin, L.; Mahapatra, D.P.; Manko, V.; Martin, M.; Martinez, G.; Maximov, A.; Mgebrichvili, G.; Miake, Y.; Mir, Md.F.; Mishra, G.C.; Mitamoto, Y.; Mohanti, B.; Mora, M.-J.; Morrison, D.; Mukhopadhyay, D.S.; Naef, H.; Nandi, B.K.; Nayak, S.K.; Nayak, T.K.; Neumaier, S.
Results on transverse mass spectra of neutral pious measured at central rapidity are presented for impact parameter selected 158-A GeV Pb + Pb-1 and Pb + Nb collisions. The distributions cover the range 0.5 GeV/c(2) less than or equal to MT - Mo less than or equal to 4 GeV/c(2). The change of the
Metastable Pions in Dense Media
Loewe, Marcelo; Villavicencio, Cristian
2016-01-01
We study the leptonic decay of charged pions in a compact star environment. Considering leptons as a degenerated Fermi system, pions are tightly constrained to decay into these particles because their Fermi levels are occupied. Thus, pion decay is only possible through thermal fluctuations. Under these circumstances, pion life-time is larger and hence can be considered to reach a metastable state. We explore restrictions under which such a metastability is possible. We also study conditions for pion-lepton chemical equilibrium and obtain the neutrino emissivity from metastable pions. Scenarios which favor this metastable state are protoneutron stars.
Model Selection for Pion Photoproduction
Landay, J; Fernández-Ramírez, C; Hu, B; Molina, R
2016-01-01
Partial-wave analysis of meson and photon-induced reactions is needed to enable the comparison of many theoretical approaches to data. In both energy-dependent and independent parametrizations of partial waves, the selection of the model amplitude is crucial. Principles of the $S$-matrix are implemented to different degree in different approaches, but a many times overlooked aspect concerns the selection of undetermined coefficients and functional forms for fitting, leading to a minimal yet sufficient parametrization. We present an analysis of low-energy neutral pion photoproduction using the Least Absolute Shrinkage and Selection Operator (LASSO) in combination with criteria from information theory and $K$-fold cross validation. These methods are not yet widely known in the analysis of excited hadrons but will become relevant in the era of precision spectroscopy. The principle is first illustrated with synthetic data, then, its feasibility for real data is demonstrated by analyzing the latest available measu...
Pion production off the nucleon
Alam, M Rafi; Chauhan, Shikha; Singh, S K
2016-01-01
We have studied charged current neutrino/antineutrino induced weak pion production from nucleon. For the present study, contributions from $\\Delta(1232)$-resonant term, non-resonant background terms as well as contribution from higher resonances viz. $P_{11}$(1440), $D_{13}$(1520), $S_{11}$(1535), $S_{11}$(1650) and $P_{13}$(1720) are taken. To write the hadronic current for the non-resonant background terms, a microscopic approach based on SU(2) non-linear sigma model has been used. The vector form factors for the resonances are obtained from the helicity amplitudes provided by MAID. Axial coupling in the case of $\\Delta(1232)$ resonance is obtained by fitting the ANL and BNL $\
Ghebache, Siham; Tribeche, Mouloud
2017-10-01
The problem of arbitrary amplitude ion-acoustic solitary waves (IASWs), which accompany electronegative plasmas having positive ions, negative ions, and nonextensive electrons is addressed. The energy integral equation with a new Sagdeev potential is analyzed to examine the existence regions of the IASWs. Different types of electronegative plasmas inspired from the experimental studies of Ichiki et al. (2001) are discussed. Our results show that in such plasmas IASWs, the amplitude and nature of which depend sensitively on the mass and density ratio of the positive and negative ions as well as the q-nonextensive parameter, can exist. Interestingly, one finds that our plasma model supports the coexistence of smooth rarefactive and spiky compressive IASWs. Our results complement and provide new insights on previously published findings on this problem.
Theissen, J; Lunkenheimer, P P; Niederer, P; Bush, E; Frieling, G; Lawin, P
1987-09-01
The pattern of intrapulmonary pressure distribution was studied during high-frequency ventilation in order to explain the inconsistent results reported in the literature. Methods. Pressure and flow velocity (hot-wire anemometry) were measured in different lung compartments: 1. In transalveolar chambers sealed to the perforated pleural surfaces of dried pig lungs; 2. In emphysema-simulating airbags sealed to the isolated bronchial trees of dried pig lungs; and 3. In transalveolar chambers sealed to the perforated pleural surfaces of freshly excised pig lungs. Results. 1. The pressure amplitudes change from one area to another and depending on the exciting frequency. 2. High-frequency oscillation is associated with an increase in pressure amplitude when the exciting frequency rises, whereas with conventional high-frequency jet ventilation the pressure amplitude is more likely to decrease with frequency. 3. During high-frequency jet ventilation the local pressure amplitude changes with the position of the tube in the trachea rather than with the exciting frequency. 4. When the volume of the measuring chamber is doubled the resulting pressure amplitude falls to half the control value. 5. The pressure amplitude and mean pressure measured in the transalveolar chamber vary more or less independently from the peak flow velocity. High-frequency ventilation is thus seen to be a frequency-dependant, inhomogeneous mode of ventilation that can essentially be homogenized by systematically changing the exciting frequency. The frequency-dependant response to different lung areas to excitation is likely to result from an intrabronchially-localized aerodynamic effect rather than the mechanical properties of the lung parenchyma.
Hoque, Romy; McCarty, David E; Chesson, Andrew L
2013-01-15
Excessive fragmentary myoclonus (EFM) consists of brief, asynchronous, twitch-like movements appearing asymmetrically in sleep. The new AASM Manual for the Scoring of Sleep and Associated Events identifies some EFM scoring criteria but does not provide amplitude criteria for scoring EFM. Older observational series have used 50 μVs. We report data from various amplitude criteria using blinded comparisons. EFMs were analyzed on the polysomnograms of 8 patients (7 men and 1 woman, mean age 57 years, range: 47-79) using a standardized protocol for sensitivity, tonus threshold, impedance, amplitude measurements, and sleep stage. The first 20 minutes each of wake, Stage 1-2, SWS, and REM were analyzed. EFMs ≥ 25, ≥ 40, and ≥ 50 microvolts (μVs) in negative deflection above the baseline were counted in tibialis anterior muscle electromyography (EMG) channels bilaterally. The mean EFM index per minute for wake, regardless of impedance, was: 7.19 ± 5.90 for ≥ 25 μV amplitude; 2.43 ± 2.02 for ≥ 40 μVs; and 2.08 ± 2.23 for ≥ 50 μVs. For sleep stages, the EFM index by stage and amplitude criteria used for measurements were: Stage 1-2: 7.38 ± 5.79 for ≥ 25 μVs; 3.13 ± 3.33 for ≥ 40 μVs; and 2.36 ± 2.66 for ≥ 50 μVs; SWS: 10.05 ± 8.04 for ≥ 25 μVs; 2.71 ± 3.13 for ≥ 40 μVs; and 1.38 ± 1.92 for ≥ 50 μVs; Total REM: 15.96 ± 11.32 for ≥ 25 μVs; 6.32 ± 4.25 for ≥ 40 μVs; and 3.94 ± 3.73 for ≥ 50 μVs; Phasic REM: 19.69 ± 15.45 for ≥ 25 μVs; 8.63 ± 7.06 for ≥ 40 μVs; and 5.52 ± 6.44 for ≥ 50 μVs; Non-phasic REM: 13.93 ± 11.31 for ≥ 25 μVs; 5.16 ± 3.57 for ≥ 40 μVs; and 3.20 ± 2.92 for ≥ 50 μVs. EFM rates increase with SWS and total REM with the highest EFM rates occurring during phasic REM. EFM rates were increased across all sleep stages when impedance was > 30 KΩ.
nuSTORM Pion Beamline Design Update
Energy Technology Data Exchange (ETDEWEB)
Liu, A. [Indiana U.; Bross, A. [Fermilab; Neuffer, D. [Fermilab; Lee, S. Y. [Indiana U.
2013-09-01
A facility producing neutrinos from muons that decay in a racetrack ring can provide extremely well understood neutrino beams for oscillation physics and the search for sterile neutrinos. The “neutrinos from STORed Muons” (nuSTORM) facility based on this idea has been introduced by Bross, Neuffer et al. The design of the nuSTORM facility and the particle tracking have been presented in the paper of Liu, et al. This paper demonstrates the recent optimization results of the pion beamline, with G4beamline simulations. The optimum choice of pion beam center momentum, a new algorithm on fitting bivariate Gaussian distribution to the pion phase space data at the downstream side of the horn, and the comparison of the beamline performance with the optics designed based on Graphite and Inconel targets are also described.
Roy-Steiner-equation analysis of pion-nucleon scattering
Meißner, U.-G.; Ruiz de Elvira, J.; Hoferichter, M.; Kubis, B.
2017-03-01
Low-energy pion-nucleon scattering is relevant for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. In this talk, we show how the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy-Steiner equations, with modern high-precision data on hadronic atoms allows one to determine the pion-nucleon scattering amplitudes at low energies with unprecedented accuracy. Special attention will be paid to the extraction of the pion-nucleon σ-term, and we discuss in detail the current tension with recent lattice results, as well as the determination of the low-energy constants of chiral perturbation theory.c
Laminar distribution of phase-amplitude coupling of spontaneous current sources and sinks
Directory of Open Access Journals (Sweden)
Roberto C Sotero
2015-12-01
Full Text Available Although resting-state functional connectivity is a commonly used neuroimaging paradigm, the underlying mechanisms remain unknown. Thalamo-cortical and cortico-cortical circuits generate oscillations at different frequencies during spontaneous activity. However, it remains unclear how the various rhythms interact and whether their interactions are lamina-specific. Here we investigated intra- and inter-laminar spontaneous phase-amplitude coupling (PAC. We recorded local-field potentials using laminar probes inserted in the forelimb representation of rat area S1. We then computed time-series of frequency-band- and lamina-specific current source density (CSD, and PACs of CSD for all possible pairs of the classical frequency bands in the range of 1–150 Hz. We observed both intra- and inter-laminar spontaneous PAC. Of 18 possible combinations, 12 showed PAC, with the highest measures of interaction obtained for the pairs of the theta/gamma and delta/gamma bands. Intra- and inter-laminar PACs involving layers 2/3–5a were higher than those involving layer 6. Current sinks (sources in the delta band were associated with increased (decreased amplitudes of high-frequency signals in the beta to fast gamma bands throughout layers 2/3–6. Spontaneous sinks (sources of the theta and alpha bands in layers 2/3 to 4 were on average linked to dipoles completed by sources (sinks in layer 6, associated with high (low amplitudes of the beta to fast-gamma bands in the entire cortical column. Our findings show that during spontaneous activity, delta, theta, and alpha oscillations are associated with periodic excitability, which for the theta and alpha bands is lamina--dependent. They further emphasize the differences between the function of layer 6 and that of the superficial layers, and the role of layer 6 in controlling activity in those layers. Our study links theories on the involvement of PAC in resting-state functional connectivity with previous work that
Hanakawa, Y.; Suda, N.
2009-12-01
Magnitude-frequency distribution of earthquakes follows the Gutenberg-Richter law. The slope of this law, b value, represents the relative occurrence of large and small earthquakes. Since magnitude is defined as corrected logarithmic amplitude, amplitude-frequency distribution of earthquakes is linear on log-log graph. On the other hand, that of non-volcanic tremors is linear on semi-log graph, indicating that it follows the exponential distribution, not the power-law distribution [Hiramatsu et al., 2008]. Thus the slope of amplitude-frequency distribution for tremors is equivalent to b value for earthquakes. In this study, we investigated time variation in the slope of amplitude-frequency distribution from analyses of tremor activities in the Bungo Channel region, where long-term slow slip events occurred in 1997 and 2003. We analyzed vertical-component records from Hi-net and the seismic networks of Japan Meteorological Agency and universities for the five-year period between 2004 and 2008. We also used records from the temporal seismic station in Hiburi Island installed by us in the period after Sept. 2004. In the Bungo Channel region, tremor activity occurs with a recurrence interval of approximately two months. We observed a total of 35 activities including small ones in the analysis period. To detect tremors and determine their hypocenters, we used the same software as Automatic Tremor Monitoring System (ATMOS) [Suda et al., in press]. We obtained frequency distribution of reduced displacements (RDs) for each tremor activity. RD is RMS amplitude of ground displacement corrected with hypocentral distance [Aki and Koyanagi, 1981], and it is proportional to seismic moment rate. The observed slopes of RD-frequency distribution for active swarms were approximately constant in the period between 2004 and 2006, but they declined in 2007. At the end of 2008, the slopes decreased bellow half the values between 2004 and 2006. As well as b value, the slope represents
Timofeev, Vladislav
2016-07-01
As part of the Yakut complex systems by measuring the intensity of cosmic rays has a unique device spherical - ionization chamber ASK-1 with a lead screen thickness of 12 cm. The camera allows you to explore the physical characteristics of the so-called "ionization jerks " - sharp increases ionization current caused by the passage through the device much ionizing particles of cosmic origin. Due to a large increase in current nuclear cascade "showers", formed mainly by particles of cosmic rays in the camera screen. Over the entire period of observation (50 years old) camera ASK-1 was registered 59125 aftershocks. Their nature and properties still does not sufficiently studied, especially in medium and large amplitudes.
Chatrchyan, Serguei; Sirunyan, Albert M; Tumasyan, Armen; Adam, Wolfgang; Aguilo, Ernest; Bergauer, Thomas; Dragicevic, Marko; Erö, Janos; Fabjan, Christian; Friedl, Markus; Fruehwirth, Rudolf; Ghete, Vasile Mihai; Hammer, Josef; Hörmann, Natascha; Hrubec, Josef; Jeitler, Manfred; Kiesenhofer, Wolfgang; Knünz, Valentin; Krammer, Manfred; Krätschmer, Ilse; Liko, Dietrich; Mikulec, Ivan; Pernicka, Manfred; Rahbaran, Babak; Rohringer, Christine; Rohringer, Herbert; Schöfbeck, Robert; Strauss, Josef; Taurok, Anton; Waltenberger, Wolfgang; Walzel, Gerhard; Widl, Edmund; Wulz, Claudia-Elisabeth; Mossolov, Vladimir; Shumeiko, Nikolai; Suarez Gonzalez, Juan; Bansal, Sunil; Cornelis, Tom; De Wolf, Eddi A; Janssen, Xavier; Luyckx, Sten; Mucibello, Luca; Ochesanu, Silvia; Roland, Benoit; Rougny, Romain; Selvaggi, Michele; Staykova, Zlatka; Van Haevermaet, Hans; Van Mechelen, Pierre; Van Remortel, Nick; Van Spilbeeck, Alex; Blekman, Freya; Blyweert, Stijn; D'Hondt, Jorgen; Gonzalez Suarez, Rebeca; Kalogeropoulos, Alexis; Maes, Michael; Olbrechts, Annik; Van Doninck, Walter; Van Mulders, Petra; Van Onsem, Gerrit Patrick; Villella, Ilaria; Clerbaux, Barbara; De Lentdecker, Gilles; Dero, Vincent; Gay, Arnaud; Hreus, Tomas; Léonard, Alexandre; Marage, Pierre Edouard; Reis, Thomas; Thomas, Laurent; Vander Marcken, Gil; Vander Velde, Catherine; Vanlaer, Pascal; Wang, Jian; Adler, Volker; Beernaert, Kelly; Cimmino, Anna; Costantini, Silvia; Garcia, Guillaume; Grunewald, Martin; Klein, Benjamin; Lellouch, Jérémie; Marinov, Andrey; Mccartin, Joseph; Ocampo Rios, Alberto Andres; Ryckbosch, Dirk; Strobbe, Nadja; Thyssen, Filip; Tytgat, Michael; Verwilligen, Piet; Walsh, Sinead; Yazgan, Efe; Zaganidis, Nicolas; Basegmez, Suzan; Bruno, Giacomo; Castello, Roberto; Ceard, Ludivine; Delaere, Christophe; Du Pree, Tristan; Favart, Denis; Forthomme, Laurent; Giammanco, Andrea; Hollar, Jonathan; Lemaitre, Vincent; Liao, Junhui; Militaru, Otilia; Nuttens, Claude; Pagano, Davide; Pin, Arnaud; Piotrzkowski, Krzysztof; Schul, Nicolas; Vizan Garcia, Jesus Manuel; Beliy, Nikita; Caebergs, Thierry; Daubie, Evelyne; Hammad, Gregory Habib; Alves, Gilvan; Correa Martins Junior, Marcos; De Jesus Damiao, Dilson; Martins, Thiago; Pol, Maria Elena; Henrique Gomes E Souza, Moacyr; Aldá Júnior, Walter Luiz; Carvalho, Wagner; Custódio, Analu; Melo Da Costa, Eliza; De Oliveira Martins, Carley; Fonseca De Souza, Sandro; Matos Figueiredo, Diego; Mundim, Luiz; Nogima, Helio; Oguri, Vitor; Prado Da Silva, Wanda Lucia; Santoro, Alberto; Soares Jorge, Luana; Sznajder, Andre; Souza Dos Anjos, Tiago; Bernardes, Cesar Augusto; De Almeida Dias, Flavia; Tomei, Thiago; De Moraes Gregores, Eduardo; Lagana, Caio; Da Cunha Marinho, Franciole; Mercadante, Pedro G; Novaes, Sergio F; Padula, Sandra; Genchev, Vladimir; Iaydjiev, Plamen; Piperov, Stefan; Rodozov, Mircho; Stoykova, Stefka; Sultanov, Georgi; Tcholakov, Vanio; Trayanov, Rumen; Vutova, Mariana; Dimitrov, Anton; Hadjiiska, Roumyana; Kozhuharov, Venelin; Litov, Leander; Pavlov, Borislav; Petkov, Peicho; Bian, Jian-Guo; Chen, Guo-Ming; Chen, He-Sheng; Jiang, Chun-Hua; Liang, Dong; Liang, Song; Meng, Xiangwei; Tao, Junquan; Wang, Jian; Wang, Xianyou; Wang, Zheng; Xiao, Hong; Xu, Ming; Zang, Jingjing; Zhang, Zhen; Asawatangtrakuldee, Chayanit; Ban, Yong; Guo, Shuang; Guo, Yifei; Li, Wenbo; Liu, Shuai; Mao, Yajun; Qian, Si-Jin; Teng, Haiyun; Wang, Dayong; Zhang, Linlin; Zhu, Bo; Zou, Wei; Avila, Carlos; Gomez, Juan Pablo; Gomez Moreno, Bernardo; Osorio Oliveros, Andres Felipe; Sanabria, Juan Carlos; Godinovic, Nikola; Lelas, Damir; Plestina, Roko; Polic, Dunja; Puljak, Ivica; Antunovic, Zeljko; Kovac, Marko; Brigljevic, Vuko; Duric, Senka; Kadija, Kreso; Luetic, Jelena; Morovic, Srecko; Attikis, Alexandros; Galanti, Mario; Mavromanolakis, Georgios; Mousa, Jehad; Nicolaou, Charalambos; Ptochos, Fotios; Razis, Panos A; Finger, Miroslav; Finger Jr, Michael; Assran, Yasser; Elgammal, Sherif; Ellithi Kamel, Ali; Khalil, Shaaban; Mahmoud, Mohammed; Radi, Amr; Kadastik, Mario; Müntel, Mait; Raidal, Martti; Rebane, Liis; Tiko, Andres; Eerola, Paula; Fedi, Giacomo; Voutilainen, Mikko; Härkönen, Jaakko; Heikkinen, Mika Aatos; Karimäki, Veikko; Kinnunen, Ritva; Kortelainen, Matti J; Lampén, Tapio; Lassila-Perini, Kati; Lehti, Sami; Lindén, Tomas; Luukka, Panja-Riina; Mäenpää, Teppo; Peltola, Timo; Tuominen, Eija; Tuominiemi, Jorma; Tuovinen, Esa; Ungaro, Donatella; Wendland, Lauri; Banzuzi, Kukka; Karjalainen, Ahti; Korpela, Arja; Tuuva, Tuure; Besancon, Marc; Choudhury, Somnath; Dejardin, Marc; Denegri, Daniel
2013-01-01
First measurements of the azimuthal anisotropy of neutral pions produced in PbPb collisions at a center-of-mass energy of $\\sqrt{s_{NN}}$ = 2.76 TeV are presented. The amplitudes of the second Fourier component ($v_2$) of the neutral pion azimuthal distributions are extracted using an event-plane technique. The values of $v_2$ are studied as a function of the neutral pion transverse momentum ($p_T$) for different classes of collision centrality in the kinematic range 1.6 < $p_T$ < 8.0 GeV, within the pseudorapidity interval |$\\eta$| < 0.8. The CMS measurements of $v_2(p_T)$ are similar to previously reported neutral pion azimuthal anisotropy results from $\\sqrt{s_{NN}}$ = 200 GeV AuAu collisions at RHIC, despite a factor of about 14 increase in the center-of-mass energy. In the momentum range 2.5 < $p_T$ < 5.0 GeV, the neutral pion anisotropies are found to be smaller than those observed by CMS for inclusive charged particles.
Form Factors in radiative pion decay
Mateu, V
2007-01-01
We perform an analysis of the form factors that rule the structure-dependent amplitude in the radiative pion decay. The resonance contributions to pion -> e nu_e gamma decays are computed through the proper construction of the vector and axial-vector form factors by setting the QCD driven asymptotic properties of the three-point Green functions VVP and VAP, and by demanding the smoothing of the form factors at high transfer of momentum. A comparison between theoretical and experimental determinations of the form factors is also carried out. We also consider and evaluate the role played by a non-standard tensor form factor. We conclude that, at present and due to the hadronic incertitudes, the search for New Physics in this process is not feasible.
Gao, Fei; Liu, Yu-xin
2016-01-01
We propose a new numerical method to compute parton distribution amplitude(PDA) from the Euclidean Bethe-Salpeter wave function. The essential step is to extract the weight function in the Nakanishi representation of the Bethe-Salpeter wave function in Euclidean space, which is an ill-posed inversion problem, via the maximum entropy method(MEM). The Nakanishi weight function as well as the corresponding light-front PDA can be well determined. We confirm the previous works on PDA computation therein the different method has been performed.
Leading order multi-soft behaviors of tree amplitudes in NLSM
Du, Yi-Jian
2016-01-01
In this paper, we investigate multi-soft behaviors of tree amplitudes in nonlinear sigma model (NLSM). We prove that the leading behaviors of amplitudes with odd number of all adjacent soft pions are zero. We further propose and prove the leading behaviors of amplitudes with even number of all adjacent soft pions. The soft factors for this case are expressed in terms of products of the leading order Berends- Giele sub-currents in Cayley parametrization. Each sub-current in the expression contains at most one hard pion. We generalize our discussion to amplitudes containing arbitrary number of nonadjacent soft blocks: The leading behaviors of amplitudes where at least one soft block has odd number of adjacent soft pions are zero; The leading soft factors for amplitudes where all soft blocks containing even number of soft pions are given by products of soft factors for all blocks.
Leading order multi-soft behaviors of tree amplitudes in NLSM
Du, Yi-Jian; Luo, Hui
2017-03-01
In this paper, we investigate multi-soft behaviors of tree amplitudes in nonlinear sigma model (NLSM). The leading behaviors of amplitudes with odd number of all-adjacent soft pions are zero. We further propose and prove that leading soft factors of amplitudes with even number all-adjacent soft pions can be expressed in terms of products of the leading order Berends-Giele sub-currents in Cayley parametrization. Each subcurrent in the expression contains at most one hard pion. Discussions are generalized to amplitudes containing arbitrary number of nonadjacent soft blocks: the leading behaviors of amplitudes where at least one soft block has odd number of adjacent soft pions are zero; the leading soft factors for amplitudes where all soft blocks containing even number of soft pions are given by products of soft factors for these blocks.
Influence of Multiple Scattering on Two-Pion Correlation Measurements
Institute of Scientific and Technical Information of China (English)
TANG Gui-Xin; ZHANG Wei-Ning; LIU Yi-Ming; HUO Lei; ZHANG Jing-Bo
2004-01-01
@@ Using the relativistic quantum molecular dynamics model, we study the influence of multiple scattering on the result of two-pion correlation measurements. The scales of pion spatial distribution are larger at thermal freezeout than at chemical freeze-out. By varying the value of the parameter of cross section from 0 to 90mb, we find that the sizes of pion source measured by two-particle correlation functions are almost independent of the parameter of cross section. However, λ parameters are sensitive to the parameter of cross section.
1992-01-01
The real particles produced in the decay of a positive pion can be seen in this image from a streamer chamber. Streamer chambers consist of a gas chamber through which a strong pulsed electric field is passed, creating sparks as a charged particle passes through it. A magnetic field is added to cause the decay products to follow curved paths so that their charge and momentum can be measured.
Exclusive electroproduction of two pions at HERA
Energy Technology Data Exchange (ETDEWEB)
Abramowicz, H. [Tel Aviv Univ. (Israel). School of Physics; Max Planck Institute for Physics, Munich (Germany); Abt, I. [Max Planck Institute for Physics, Munich (Germany); Adamczyk, L. [AGH-Univ. of Science and Technology, Krakow (PL). Faculty of Physics and Applied Computer Science] (and others)
2011-11-15
The exclusive electroproduction of two pions in the mass range 0.4< M{sub {pi}}{sub {pi}} <2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb{sup -1}. The analysis was carried out in the kinematic range of 2< Q{sup 2}<80 GeV{sup 2}, 32
Exclusive electroproduction of two pions at HERA
Abramowicz, H
2012-01-01
The exclusive electroproduction of two pions in the mass range 0.4 < M{\\pi}{\\pi} < 2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb-1. The analysis was carried out in the kinematic range of 2 < Q2 < 80 GeV2, 32 < W < 180 GeV and |t| < 0.6 GeV2, where Q2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |F(M{\\pi}{\\pi})|, assuming that the studied mass range includes the contributions of the {\\rho}, {\\rho}' and {\\rho}" vector-meson states. The masses and widths of the resonances were obtained and the Q2 dependence of the cross-section ratios {\\sigma}({\\rho}' \\rightarrow {\\pi}{\\pi})/{\\sigma}({\\rho}) and {\\sigma}({\\rho}" \\rightarrow {\\pi}{\\pi})/{\\sigma}({\\rho}) was extracted. The pion form factor obtained in the present analysis is compared to that obtained...
Can pions created in high-energy heavy-ion collisions produce a Centauro-type effect?
Martinis, M; Martinis, M; Mikuta-Martinis, V
1994-01-01
We study a Centauro-type phenomenon in high-energy heavy-ion collisions by assuming that pions are produced semiclassically both directly and in pairs through the isovector channel. The leading-particle effect and the factorization property of the scattering amplitude in the impact-parameter space are used to define the classical pion field. By analyzing the joint probability function P_{II_{3}}(n_{0},n_{ \\_}) for producing n_{0} neutral and n_{-} negative pions from a definite isospin state II_{3} of the incoming leading-particle system we show that only direct production of pions without isovector pairs favors Centauro-type behavior. The presence of isovector pairs seems to destroy the effect. Our conclusion is supported through the calculation of two pion correlation parameters, f_{2}^{0-} and f_{2}^{00}, and the average number of neutral pions ( \\langle n_{0} \\rangle_{n_{ \\_}}) as a function of negative pions (n_{ \\_}) produced.
Pion Polarizability at CERN COMPASS
Moinester, Murray
2014-01-01
The electric α π and magnetic β π charged p ion polariz abilities characterize the induced dipole moments of the pion during γπ scattering . The se fundamental characterisitcs of the pion provide stringent tests of various theoretical models , for example chiral perturbation theory ( Ch PT) . CERN COMPAS S investigated pion Compton scattering γπ → γ π , via radiative pion Primakoff scattering (Bremsstrahlung of 190 GeV/c negative pions) in the nuclear Coulomb field of the Ni nucleus: π + Ni → π + γ + Ni. The resulting data are equivalent to γπ Compton scatter ing for laboratory γ's having momenta of order 1 GeV/c incident on a target pion at rest. The data yield preliminary polarizability values α π = − β π = (1.9±0.7 stat ±0.8 syst ) ×10 − 4 fm 3 , in agreement with Ch PT .
Pion absorption on {sup 3}He at low energies
Energy Technology Data Exchange (ETDEWEB)
Hahn, H.; Altman, A.; Ashery, D.; Gefen, G.; Gill, D.R.; Johnson, R.R.; Levy-Nathansohn, R.; Moinester, M.A.; Sevior, M.; Trelle, R.P. [Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics and Astronomy, Tel Aviv University, 69978 Ramat Aviv (Israel)]|[TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (CANADA)]|[Department of Physics, University of British Columbia, Vancouver, British Columbia, V6T 2A6 (CANADA)
1996-03-01
The reactions {sup 3}He({pi}{sup +},{ital pp}){ital p} and {sup 3}He({pi}{sup {minus}},{ital pn}){ital n} were studied at 37.0 MeV by coincidence detection of two nucleons. The differential cross sections were separated to two-nucleon ({sigma}{sub 2{ital N}}), three-nucleon ({sigma}{sub 3{ital N}}), and final-state interaction ({sigma}{sub FSI}) components. For {pi}{sup +}, the {sigma}{sub 2{ital N}} angular distribution is symmetric about 90{degree}, and the total cross section is 1.5 times the cross section measured for {ital d}({pi}{sup +},{ital pp}). For {pi}{sup {minus}}, the angular distribution is asymmetric (backward peaked). The asymmetry increases with decreasing energy, indicating increasing pion {ital s}-wave contribution at lower energies. The fraction of the cross section induced by {ital s}-wave pions as calculated by a partial wave amplitude analysis is 13{percent}. The measured total cross sections are {sigma}{sub 2{ital N}}({pi}{sup {minus}})=0.85{plus_minus}0.08 mb and {sigma}{sub 2{ital N}}({pi}{sup +})=7.9{plus_minus}0.5 mb; {sigma}{sub 3{ital N}}({pi}{sup {minus}})=1.6{plus_minus}0.7 mb and {sigma}{sub 3{ital N}}({pi}{sup +})=1.3{plus_minus}0.3 mb. A new evaluation of {sigma}{sub 3{ital N}} at {ital T}{sub {pi}}=62.5 and 82.8 MeV is given, using data from an earlier experiment. The cross sections leading to the two-nucleon final-state interaction at {ital T}{sub {pi}}=37.0 MeV are also estimated. {copyright} {ital 1996 The American Physical Society.}
Determination of the pion and kaon structure functions
Energy Technology Data Exchange (ETDEWEB)
Aitkenhead, W.; Barton, D.S.; Brandenburg, G.W.; Busza, W.; Dobrowolski, T.; Friedman, J.I.; Kendall, H.W.; Lyons, T.; Nelson, B.; Rosenson, L.; Toy, W.; Verdier, R.; Votta, L.; Chiaradia, M.T.; DeMarzo, C.; Favuzzi, C.; Germinario, G.; Guerriero, L.; LaVopa, P.; Maggi, G.; Posa, F.; Selvaggi, G.; Spinelli, P.; Waldner, F.; Brenner, A.E.; Carey, D.C.; Elias, J.E.; Garbincius, P.H.; Mikenberg, G.; Polychronakos, V.A.; Meunier, R.; Cutts, D.; Dulude, R.S.; Lanou, R.E. Jr.; Massimo, J.T.
1980-07-21
Quark structure functions have been extracted from low-p/sub T/ inclusive hadron production data for the pion and kaon with use of the recombination model. n/sup ..pi../=1.0 +- 0.1 and n/sup K/=2.5 +- 0.6 is obtained, where n is the leading (1-x) power of the nonstrange--valence-quark distribution. Both the pion and kaon nonstrange--sea-quark functions have napprox. =3.5.
HBT correlations and charge ratios in multiple production of pions
Bialas, A
1999-01-01
The influence of the HBT effect on the multiplicity distribution and charge ratios of independently produced pions is studied. It is shown that, for a wide class of models, there is a critical point, where the average number of pions becomes very large and the multiplicity distibution becomes very broad. In this regime unusual charge ratios ("centauros", "anticentauros") are strongly enhanced. The prospects for reaching this regime are discussed.
Model selection for pion photoproduction
Landay, J.; Döring, M.; Fernández-Ramírez, C.; Hu, B.; Molina, R.
2017-01-01
Partial-wave analysis of meson and photon-induced reactions is needed to enable the comparison of many theoretical approaches to data. In both energy-dependent and independent parametrizations of partial waves, the selection of the model amplitude is crucial. Principles of the S matrix are implemented to a different degree in different approaches; but a many times overlooked aspect concerns the selection of undetermined coefficients and functional forms for fitting, leading to a minimal yet sufficient parametrization. We present an analysis of low-energy neutral pion photoproduction using the least absolute shrinkage and selection operator (LASSO) in combination with criteria from information theory and K -fold cross validation. These methods are not yet widely known in the analysis of excited hadrons but will become relevant in the era of precision spectroscopy. The principle is first illustrated with synthetic data; then, its feasibility for real data is demonstrated by analyzing the latest available measurements of differential cross sections (d σ /d Ω ), photon-beam asymmetries (Σ ), and target asymmetry differential cross sections (d σT/d ≡T d σ /d Ω ) in the low-energy regime.
CP violation and kaon-pion interactions in B {r_arrow} K {pi}{sup +}{pi}{sup -} decays.
Energy Technology Data Exchange (ETDEWEB)
El-Bennich, B.; Furman, A.; Kaminski, R.; Lesniak, L.; Loiseau, B.; Moussallam, B.; Physics; Univ. Pierre et Marie Curie; ul. Bronowicka; Polish Academy of Sciences; Univ. Paris-Sud
2009-01-01
We study CP violation and the contribution of the strong kaon-pion interactions in the three-body B {yields} Kpi{sup +}pi{sup -} decays. We extend our recent work on the effect of the two-pion S- and P-wave interactions to that of the corresponding kaon-pion ones. The weak amplitudes have a first term derived in QCD factorization and a second one as a phenomenological contribution added to the QCD penguin amplitudes. The effective QCD coefficients include the leading order contributions plus next-to-leading order vertex and penguins corrections. The matrix elements of the transition to the vacuum of the kaon-pion pairs, appearing naturally in the factorization formulation, are described by the strange Kpi scalar (S-wave) and vector (P-wave) form factors. These are determined from Muskhelishvili-Omnes coupled channel equations using experimental kaon-pion T-matrix elements, together with chiral symmetry and asymptotic QCD constraints. From the scalar form factor study, the modulus of the K*{sub 0}(1430) decay constant is found to be (32 {+-} 5) MeV. The additional phenomenological amplitudes are fitted to reproduce the Kpi effective mass and helicity angle distributions, the B {yields} K*(892)pi branching ratios and the CP asymmetries of the recent data from Belle and BABAR collaborations. We use also the new measurement by the BABAR group of the phase difference between the B{sup 0} and [overline B]{sup 0} decay amplitudes to K*(892)pi. Our predicted B{sup {+-}} {yields} K*{sub 0}(1430)pi{sup {+-}}, K*{sub 0}(1430) {yields} K{sup {+-}}pi{sup {-+}} branching fraction, equal to (11.6 {+-} 0.6) x 10{sup -6}, is smaller than the result of the analyzes of both collaborations. For the neutral B{sup 0} decays, the predicted value is (11.1 {+-} 0.5) x 10{sup -6}. In order to reduce the large systematic uncertainties in the experimental determination of the B {yields} K*{sub 0}(1430)pi branching fractions, a new parametrization is proposed. It is based on the Kpi scalar
Charged Pion Energy Reconstruction in the ATLAS Barrel Calorimeter
Bosman, M; Nessi, Marzio
2000-01-01
The intrinsic performance of the ATLAS barrel and extended barrelcalorimeters for the measurement of charged pions is presented. Pion energyscans (E = 20, 50, 200, 400 and 1000 GeV) at two pseudo-rapidity points ($\\eta$= 0.3 and 1.3) and pseudorapidity scans ($-0.2 < \\eta < 1.8$) with pions ofconstant transverse energy ($E_T = 20$ and 50 GeV) are analysed. A simpleapproach, that accounts in first order for non-compensation and dead materialeffects, is used for the pion energy reconstruction. The intrinsic performancesof the calorimeter are studied: resolution, linearity, effect of dead material,tails in the energy distribution. The effect of electronic noise, cell energycuts and restricted cone size are investigated.
Study of Di-Pion Transitions Among Upsilon(3S), Upsilon(2S), and Upsilon(1S) States
Cronin-Hennessy, D; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Smith, A; Zweber, P; Dobbs, S; Metreveli, Z V; Seth, K K; Tomaradze, A G; Ernst, J; Ecklund, K M; Severini, H; Love, W; Savinov, V; López, A; Mehrabyan, S; Méndez, H; Ramírez, J; Huang, G S; Miller, D H; Pavlunin, V; Sanghi, B; Shipsey, I P J; Xin, B; Adams, G S; Anderson, M; Cummings, J P; Danko, I; Hu, D; Moziak, B; Napolitano, J; He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Yang, F; Artuso, M; Blusk, S; Khalil, S; Li, J; Menaa, N; Mountain, R; Nisar, S; Randrianarivony, K; Sia, R; Skwarnicki, T; Stone, S; Wang, J C; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Pappas, S P; Weinstein, A J; Asner, D M; Edwards, K W; Naik, P; Briere, R A; Ferguson, T; Tatishvili, G T; Vogel, H; Watkins, M E; Rosner, J L; Adam, N E; Alexander, J P; Cassel, D G; Duboscq, J E; Ehrlich, R; Fields, L; Galik, R S; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Jones, C D; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Mahlke-Krüger, H; Mohapatra, D; Onyisi, P U E; Patterson, J R; Peterson, D; Pivarski, J; Riley, D; Ryd, A; Sadoff, A J; Schwarthoff, H; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Athar, S B; Patel, R; Yelton, J; Rubin, P; Cawlfield, C; Eisenstein, B I; Karliner, I; Kim, D; Lowrey, N; Selen, M; White, E J; Wiss, J; Mitchell, R E; Shepherd, M R; Besson, D; Pedlar, T K
2007-01-01
We present measurements of decay matrix elements for hadronic transitions of the form Upsilon(nS) -> pi pi Upsilon(mS) where (n, m) = (3, 1), (2, 1), and (3, 2). We reconstruct charged and neutral pion modes with the final state Upsilon decaying to either mu+mu- or e+e-. Dalitz plot distributions for the twelve decay modes are fit individually as well as jointly assuming isospin symmetry, thereby measuring the matrix elements of the decay amplitude. We observe and account for the anomaly previously noted in the di-pion invariant mass distribution for the Upsilon(3S) -> pi pi Upsilon(1S) transition and obtain good descriptions of the dynamics of the decay using the most general decay amplitude allowed by partial conservation of the axial-vector current (PCAC) considerations. The fits further indicate that the Upsilon(2S) -> pi pi Upsilon(1S) and Upsilon(3S) -> pi pi Upsilon(2S) transitions also show the presence of terms in the decay amplitude that were previously ignored, although at a relatively suppressed l...
A relativistic model for neutrino pion production from nuclei in the resonance region
Praet, C; Jachowicz, N; Ryckebusch, J
2007-01-01
We present a relativistic model for electroweak pion production from nuclei, focusing on the $\\Delta$ and the second resonance region. Bound states are derived in the Hartree approximation to the $\\sigma-\\omega$ Walecka model. Final-state interactions of the outgoing pion and nucleon are described in a factorized way by means of a relativistic extension of the Glauber model. Our formalism allows a detailed study of neutrino pion production through $Q^2$, $W$, energy, angle and out-of-plane distributions.
Amaro, J E; Nieves, J; Valverde, M; Vicente-Vacas, M J
2009-01-01
We present a microscopic model for neutrino induced one-pion production off the nucleon and its implementation for the purpose of calculating coherent pion production in nuclei. We further criticize the use of the Rein--Sehgal model for coherent pion production by low energy neutrinos. In particular, we show how the approximations in that model give rise to a much flatter differential cross section in the $\\eta=E_\\pi(1-\\cos\\theta_\\pi)$ variable. We discuss the limitations intrinsic to any approach based on the partial conservation of the axial current hypothesis and the inability of such models to properly determine the angular distribution of the outgoing pion with respect to the direction of the incoming neutrino. We show the effects of those limitation for the case of the $\\frac{d\\sigma}{d\\eta}$ differential cross section.
Probing Delta structure with pion electromagnetic production
Yang, S N; Yang, Shin Nan
2003-01-01
The Dubna-Mainz-Taipei dynamical model for pion electromagnetic production, which can describe well the existing data from threshold up to 1 GeV photon lab energy, is presented and used to analyze the recent precision data in the $\\Delta$ region. We find that, within our model, the bare Delta is almost spherical while the physical Delta is oblate. The deformation is almost saturated by the pion cloud effects. We further find that up to Q^2 = 4.0 (GeV/c)^2, the extracted helicity amplitude A_{3/2} and A_{1/2} remain comparable with each other, implying that hadronic helicity is not conserved at this range of Q^2. The ratio E_{1+}/M_{1+} obtained show, starting from a small and negative value at the real photon point, a clear tendency to cross zero, and to become positive with increasing Q^2. This is a possible indication of a very slow approach toward the pQCD region. Finally, we find that the bare helicity amplitude A_{1/2} and S_{1/2}, but not A_{3/2}, starts exhibiting the scaling behavior at about Q^2 \\ge ...
Simple parametrization of the. pi. -N amplitude
Energy Technology Data Exchange (ETDEWEB)
McLeod, R.J.; Afnan, I.R.
1985-07-01
We present a simple parametrization of the S-, P-, and D-wave ..pi..-N amplitudes using separable potentials for T/sub ..pi../<1 GeV. The effect of the inelasticity is included in the Green's function while maintaining consistency with unitarity. The P/sub 11/ amplitude is written as a pole plus nonpole in order to describe pion absorption in A> or =2.
Chaoticity parameter $\\lambda$ in two-pion interferometry in an expanding boson gas model
Liu, Jie; Zhang, Wei-Ning; Wong, Cheuk-Yin
2014-01-01
We investigate the chaoticity parameter $\\lambda$ in two-pion interferometry in an expanding boson gas model. The degree of Bose-Einstein condensation of identical pions, density distributions, and Hanbury-Brown-Twiss (HBT) correlation functions are calculated for the expanding gas within the mean-field description with a harmonic oscillator potential. The results indicate that a sources with thousands of identical pions may exhibit a degree of Bose-Einstein condensation at the temperatures during the hadronic phase in relativistic heavy-ion collisions. This finite condensation may decrease the chaoticity parameter $\\lambda$ in the two-pion interferometry measurements at low pion pair momenta, but influence only slightly the $\\lambda$ value at high pion pair momentum.
Time evolution of pion emission in heavy ion collisions at SIS energies
Oeschler, H
1999-01-01
Using a magnetic spectrometer pions, kaons and protons were detected in mass-symmetric heavy ion reactions from C+C to Au+Au and at incident energies between 0.6 and 2.0 A centre dot GeV. The center-of-mass pion spectra deviate from a Boltzmann distribution for all collision systems. Results are presented indicating that high-energy pions are emitted at an early stage of the collision. This is based on (i) a comparison of pi sup + and pi sup - spectra and (ii) the shielding of pions by spectator matter in peripheral collisions.
A phenomenological determination of the pion-nucleon scattering lengths from pionic hydrogen
Ericson, Torleif Eric Oskar; Wycech, S
2005-01-01
A model independent expression for the electromagnetic corrections to a phenomenological hadronic pion-nucleon scattering length, extracted from pionic hydrogen, is obtained. In a non-relativistic approach and using an extended charge distribution, these corrections are derived up to terms of order (alpha)**2 log(alpha) in the limit of a short-range hadronic interaction. We infer a charged pion-proton scattering length of 0.0870(5) in units of inverse pion mass, which gives for the charged pion-proton-neutron coupling, through the GMO relation, a value of 14.04(17).
Pion-nucleon scattering: from chiral perturbation theory to Roy-Steiner equations
Kubis, Bastian; Hoferichter, Martin; de Elvira, Jacobo Ruiz; Meißner, Ulf-G.
2016-11-01
Ever since Weinberg's seminal predictions of the pion-nucleon scattering amplitudes at threshold, this process has been of central interest for the study of chiral dynamics involving nucleons. The scattering lengths or the pion-nucleon σ-term are fundamental quantities characterizing the explicit breaking of chiral symmetry by means of the light quark masses. On the other hand, pion-nucleon dynamics also strongly affects the long-range part of nucleon-nucleon potentials, and hence has a far-reaching impact on nuclear physics. We discuss the fruitful combination of dispersion-theoretical methods, in the form of Roy-Steiner equations, with chiral dynamics to determine pion-nucleon scattering amplitudes at low energies with high precision.*
Minkowski space pion model inspired by lattice QCD running quark mass
Mello, Clayton S.; de Melo, J. P. B. C.; Frederico, T.
2017-03-01
The pion structure in Minkowski space is described in terms of an analytic model of the Bethe-Salpeter amplitude combined with Euclidean Lattice QCD results. The model is physically motivated to take into account the running quark mass, which is fitted to Lattice QCD data. The pion pseudoscalar vertex is associated to the quark mass function, as dictated by dynamical chiral symmetry breaking requirements in the limit of vanishing current quark mass. The quark propagator is analyzed in terms of a spectral representation, and it shows a violation of the positivity constraints. The integral representation of the pion Bethe-Salpeter amplitude is also built. The pion space-like electromagnetic form factor is calculated with a quark electromagnetic current, which satisfies the Ward-Takahashi identity to ensure current conservation. The results for the form factor and weak decay constant are found to be consistent with the experimental data.
Neutral current coherent pion production
Alvarez-Ruso, L; Vacas, M J Vicente
2007-01-01
We investigate the neutrino induced coherent pion production reaction at low and intermediate energies. The model includes pion, nucleon and Delta(1232) resonance as the relevant hadronic degrees of freedom. Nuclear medium effects on the production mechanisms and pion distortion are taken into account. We obtain that the dominance of the Delta excitation holds due to large cancellations among the background contributions. We consider two sets of vector and axial-vector N-Delta transition form-factors, evidencing the strong sensitivity of the results to the axial coupling C5A(0). The differences between neutrino and antineutrino cross sections, emerging from interference terms, are also discussed.
Neutrino induced 1-pion production
González-Jiménez, R; Van Dessel, N; Pandey, V; Jachowicz, N
2016-01-01
Neutrino-induced pion production constitutes an important contribution to neutrino-nucleus scattering cross sections at intermediate energies. A deep understanding of this process is mandatory for a correct interpretation of neutrino-oscillation experiments. We aim at contributing to the ongoing effort to understand the various experimental results obtained by different collaborations in a wide range of energies. In particular, in this work we analyze recent MiniBooNE and MINERvA charged-current neutrino 1-pion production data. We use a relativistic theoretical approach which accounts for resonant and non-resonant 1-pion production contributions.
Energy Technology Data Exchange (ETDEWEB)
Haiyan Gao, Wei Chen
2009-12-01
We extracted the differential cross section for the gn --> pi-p process from a deuterium target using the CLAS detector at Jefferson Lab in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles (theta c.m.) between 50 deg. and 115 deg. We confirm a previous indication of a broad enhancement around a c.m. energy (sqrt s) of 2.1 GeV at theta c.m. =90 deg. in the scaled differential cross section, s^7 ds/dt and a rapid fall-off in a center-of-mass energy region of about 400 MeV following the enhancement. Our data show an angular dependence of this enhancement as the suggested scaling region is approached for theta c.m. from 70 deg. to 10 deg.
Energy Technology Data Exchange (ETDEWEB)
Ryong Ji, C.; Pang, A.; Szczepaniak, A. [North Carolina State Univ., Raleigh, NC (United States)
1994-04-01
It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.
Transverse target single-spin asymmetry in inclusive electroproduction of charged pions and kaons
Airapetian, Avetik; Akopov, N.; Blok, H. P.; Schnell, Gunar; Seitz, B.; Shibata, T.A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stewart, J.; Stinzing, F.; Borissov, A.; Taroian, S.
2014-01-01
Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle $\\psi$ about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum relative to the direction of the incident beam, and the Feynman variable $x_F$. The $\\sin(\\psi)$ amplitudes are positive for positive pions...
Transverse target single-spin asymmetry in inclusive electroproduction of charged pions and kaons
Airapetian, A.; Akopov, N.; Blok, H. P.; Schnell, G.; Seitz, B.; Shibata, T.A.; Shutov, V.; Stancari, M.; Statera, M.; Steffens, E.; Steijger, J. J. M.; Stewart, J.; Stinzing, F.; Borissov, A.; Taroian, S.
2013-01-01
Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle $\\psi$ about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum relative to the direction of the incident beam, and the Feynman variable $x_F$. The $\\sin(\\psi)$ amplitudes are positive for positive pions...
Neutrino induced coherent pion production
Hernández, E; Valverde, M; Vicente-Vacas, M J
2009-01-01
We discuss different parameterizations of the $C_5^A(q^2)$ $N\\Delta$ axial form factor, fitted to the old Argonne bubble chamber data for pion production by neutrinos, and we use coherent pion production to test their low $q^2$ behavior. We find moderate effects that will be difficult to observe with the accuracy of present experiments. We also discuss the use of the Rein-Sehgal model for low energy coherent pion production. By comparison to a microscopic calculation, we show the weaknesses of some of the approximations in that model that lead to very large cross sections as well as to the wrong shapes for differential ones. Finally we show that models based on the partial conservation of the axial current hypothesis are not fully reliable for differential cross sections that depend on the angle formed by the pion and the incident neutrino.
Intensity-dependent pion-nucleon coupling in multipion production processes
Martinis, M
1996-01-01
We propose an intensity-dependent pion-nucleon coupling Hamiltonian within a unitary multiparticle-production model of the Auerbach- Avin-Blankenbecler-Sugar (AABS) type in which the pion field is represented by the thermal-density matrix.Using this Hamiltonian, we explain the appearance of the negative-binomial (NB) distribution for pions and the well-known empirical relation, the so-called Wr\\' oblewski relation, in which the dispersion $D$ of the pion- multiplicity distribution is linearly related to the average multiplicity $$ : $D = A + B$, with the coefficient $A < 1$. The Hamiltonian of our model is expressed linearly in terms of the generators of the $SU(1,1)$ group.We also find the generating function for the pion field, which reduces to the generating function of the NB distribution limit $T \\to 0$.
Unitary theory of pion photoproduction in the chiral bag model
Energy Technology Data Exchange (ETDEWEB)
Araki, M.; Afnan, I.R.
1987-07-01
We present a multichannel unitary theory of single pion photoproduction from a baryon B. Here, B is the nucleon or ..delta..(1232), with possible extension to include the Roper resonance and strange baryons. We treat the baryon as a three-quark state within the framework of the gauge and chiral Lagrangian, derived from the Lagrangian for the chiral bag model. By first exposing two-body, and then three-body unitarity, taking into consideration the ..pi pi..B and ..gamma pi..B intermediate states, we derive a set of equations for the amplitudes both on and off the energy shell. The Born term in the expansion of the amplitude has the new feature that the vertices in the pole diagram are undressed, while those in the crossed, contact, and pion pole diagrams are dressed.
Unitary theory of pion photoproduction in the chiral bag model
Araki, M.; Afnan, I. R.
1987-07-01
We present a multichannel unitary theory of single pion photoproduction from a baryon B. Here, B is the nucleon or Δ(1232), with possible extension to include the Roper resonance and strange baryons. We treat the baryon as a three-quark state within the framework of the gauge and chiral Lagrangian, derived from the Lagrangian for the chiral bag model. By first exposing two-body, and then three-body unitarity, taking into consideration the ππB and γπB intermediate states, we derive a set of equations for the amplitudes both on and off the energy shell. The Born term in the expansion of the amplitude has the new feature that the vertices in the pole diagram are undressed, while those in the crossed, contact, and pion pole diagrams are dressed.
Weak pion production from nuclei
Indian Academy of Sciences (India)
S K Singh; M Sajjad Athar; Shakeb Ahmad
2006-04-01
The charged current pion production induced by neutrinos in 12C, 16O and 56Fe nuclei has been studied. The calculations have been done for the coherent as well as the incoherent processes assuming dominance and takes into account the effect of Pauli blocking, Fermi motion and the renormalization of in the nuclear medium. The pion absorption effects have also been taken into account.
Evaluation of the Axial Vector Commutator Sum Rule for Pion-Pion Scattering
Adler, Stephen L
2007-01-01
We consider the sum rule proposed by one of us (SLA), obtained by taking the expectation value of an axial vector commutator in a state with one pion. The sum rule relates the pion decay constant to integrals of pion-pion cross sections, with one pion off the mass shell. We remark that recent data on pion-pion scattering allow a precise evaluation of the sum rule. We also discuss the related Adler--Weisberger sum rule (obtained by taking the expectation value of the same commutator in a state with one nucleon), especially in connection with the problem of extrapolation of the pion momentum off its mass shell.
Choi, Ho-Meoyng
2014-01-01
We discuss the light-front zero-mode issue in the light-front quark model prediction of the twist-3 distribution amplitude of a pseudoscalar meson from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD.
Single pion contribution to the hyperfine splitting in muonic hydrogen
Huong, Nguyen Thu; Moussallam, Bachir
2015-01-01
We consider the simple one-pion exchange (Yukawa potential) contribution to the 2S hyperfine splitting in muonic hydrogen which had, until recently, been disregarded. We evaluate the relevant vertex amplitudes, in particular $\\pi^0\\mu^+\\mu^-$, combining low energy chiral expansions together with experimental data on $\\pi^0$ and $\\eta$ decays. The result for the 2S HFS is found to be small but not irrelevant.
Pion production: A probe for coherence in medium-energy heavy-ion collisions
Stachel, J.; Braun-Munzinger, P.; Freifelder, R. H.; Paul, P.; Sen, S.; Deyoung, P.; Zhang, P. H.; Awes, T. C.; Obenshain, F. E.; Plasil, F.; Young, G. R.; Fox, R.; Ronningen, R.
1986-04-01
The production of neutral pions has been studied in reactions of 35 MeV/nucleon 14N+ 27Al,Ni,W and 25 MeV/nucleon 16O+ 27Al,Ni. Inclusive pion differential distributions dσ/dTπ, dσ/dΩ, dσ/dy, dσ/dp⊥, and d2σ/dy dp⊥ have been measured by detecting the two pion-decay γ rays in a setup of 20 lead glass Cˇerenkov detector telescopes. Special care was taken to understand and suppress background events. Effects of pion reabsorption are discussed and it is found that the cross sections presented here are substantially affected by such final state interactions. The comparatively large experimental cross sections and the shape of the spectral distributions cannot be accounted for in single nucleon-nucleon collision or statistical models; they rather call for a coherent pion production mechanism.
AUTHOR|(SzGeCERN)663936; Dominik, Wojciech; Gaździck, Marek
2016-01-01
This thesis presents inclusive spectra of the negatively charged pions produced in inelastic proton-proton interactions measured at five beam momenta: 20, 31, 40, 80 and 158 GeV/c. The measurements were conducted in the NA61/SHINE experiment at CERN using a system of five Time Projection Chambers. The negatively charged pion spectra were calculated based on the negatively charged hadron spectra. Contribution of hadrons other than the primary pions was removed using EPOS simulations. The results were corrected for effects related to detection, acceptance, reconstruction efficiency and the analysis technique. Two-dimensional spectra were derived as a function of rapidity and transverse momentum or transverse mass. The spectra were parametrised by widths of the rapidity distributions, inverse slope parameters of the transverse mass distributions, mean transverse masses and the total pion multiplicities. The negatively charged pion spectra in proton-proton interactions belong to a broad NA61/SHINE programme of se...
Systematics of pion double charge exchange
Energy Technology Data Exchange (ETDEWEB)
Gilman, R.A.
1985-10-01
Differential cross sections have been measured for pion-induced double-charge-exchange (DCX) reactions leading to double-isobaric-analog states (DIAS) and low-lying nonanalog states in the residual nuclei. A description of the experimental details and data analysis is presented. The experimentally observed systematics of reactions leading to DIAS, to nonanalog ground states, and to low-lying 2 states are described. Lowest-order optical-model calculations of DIAS DCX are compared to the data. Efforts to understand the anomalies by invoking additional reaction-mechanism amplitudes and a higher-order optical potential are described. Calculations of nonanalog DCX reactions leading to J/sup / = 0 states were performed within a distorted-wave impulse-approximation framework. The sensitivities of these calculations to input parameters are discussed. 58 refs., 41 figs., 16 tabs.
Anomalous pion decay revisited
Battistel, O A; Nemes, M C; Hiller, B
1999-01-01
An implicit four dimensional regularization is applied to calculate the axial-vector-vector anomalous amplitude. The present technique always complies with results of Dimensional Regularization and can be easily applied to processes involving odd numbers of $\\gamma_5$ matrices. This is illustrated explicitely in the example of this letter.
One pion production in pp collisions at 162 GeV/c
Gnat, Y; Benary, O; Dagan, S; Grunhaus, Jacob; Levy, A; Oren, Y; Schlesinger, J
1973-01-01
A study of pp interactions at an incident momentum of 16.2 GeV/c leading to two-prong non-strange final states was carried out in an exposure of the 2m CERN hydrogen bubble chamber. The c.m. angle and momentum distributions for the outgoing particles in the final states pn pi /sup +/ and pp pi /sup 0/ are presented and discussed. These final states were analysed in terms of quasi two-body final states -N (N pi ), with the pion-nucleon system in an I=/sup 1///sub 2/ or I= /sup 3///sub 2/ state. A determination of these two isospin amplitudes and their interference terms is then carried out. The reaction pp to pn pi /sup +/ is found to be well described by a Reggeized exchange model, as well as by a double Regge-exchange model. (14 refs).
Lattice QCD study of the Boer-Mulders effect in a pion
Engelhardt, M; Musch, B; Negele, J; Schäfer, A
2015-01-01
The three-dimensional momenta of quarks inside a hadron are encoded in transverse momentum-dependent parton distribution functions (TMDs). This work presents an exploratory lattice QCD study of a TMD observable in the pion describing the Boer-Mulders effect, which is related to polarized quark transverse momentum in an unpolarized hadron. Particular emphasis is placed on the behavior as a function of a Collins-Soper evolution parameter quantifying the relative rapidity of the struck quark and the initial hadron, e.g., in a semi-inclusive deep inelastic scattering (SIDIS) process. The lattice calculation, performed at the pion mass m_pi = 518 MeV, utilizes a definition of TMDs via hadronic matrix elements of a quark bilocal operator with a staple-shaped gauge connection; in this context, the evolution parameter is related to the staple direction. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. I...
Structure of the neutral pion and its electromagnetic transition form factor
Raya, K; Bashir, A; Cobos-Martinez, J J; Gutiérrez-Guerrero, L X; Roberts, C D; Tandy, P C
2015-01-01
The $\\gamma^\\ast \\gamma \\to \\pi^0$ transition form factor, $G(Q^2)$, is computed on the entire domain of spacelike momenta using a continuum approach to the two valence-body bound-state problem in relativistic quantum field theory: the result agrees with data obtained by the CELLO, CLEO and Belle Collaborations. The analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor, and demonstrates, too, that a fully self-consistent treatment can readily connect a pion PDA that is a broad, concave function at the hadronic scale with the perturbative QCD prediction for the transition form factor in the hard photon limit. The normalisation of that limit is set by the scale of dynamical chiral symmetry breaking, which is a crucial feature of the Standard Model. Understanding of the latter will thus remain incomplete until definitive transition form factor data is available on $Q^2>10\\,$GeV$^2$.
Brown, Laurie Mark; Dresden, Max; Hoddeson, Lillian
2009-01-01
Part I. Introduction; 1. Pions to quarks: particle physics in the 1950s Laurie M Brown, Max Dresden and Lillian Hoddeson; 2. Particle physics in the early 1950s Chen Ning Yang; 3. An historian's interest in particle physics J. L. Heilbron; Part II. Particle discoveries in cosmic rays; 4. Cosmic-ray cloud-chamber contributions to the discovery of the strange particles in the decade 1947-1957 George D. Rochester; 5. Cosmic-ray work with emulsions in the 1940s and 1950s Donald H. Perkins; Part III. High-energy nuclear physics; Learning about nucleon resonances with pion photoproduction Robert L. Walker; 7. A personal view of nucleon structure as revealed by electron scattering Robert Hofstadter; 8. Comments on electromagnetic form factors of the nucleon Robert G. Sachs and Kameshwar C. Wali; Part IV. The new laboratory; 9. The making of an accelerator physicist Matthew Sands; 10. Accelerator design and construction in the 1950s John P. Blewett; 11. Early history of the Cosmotron and AGS Ernest D. Courant; 12. Panel on accelerators and detectors in the 1950s Lawrence W. Jones, Luis W. Alvarez, Ugo Amaldi, Robert Hofstadter, Donald W. Kerst, Robert R. Wilson; 13. Accelerators and the Midwestern Universities Research Association in the 1950s Donald W. Kerst; 14. Bubbles, sparks and the postwar laboratory Peter Galison; 15. Development of the discharge (spark) chamber in Japan in the 1950s Shuji Fukui; 16. Early work at the Bevatron: a personal account Gerson Goldhaber; 17. The discovery of the antiproton Owen Chamberlain; 18. On the antiproton discovery Oreste Piccioni; Part V. The Strange Particles; 19. The hydrogen bubble chamber and the strange resonances Luis W. Alvarez; 20. A particular view of particle physics in the fifties Jack Steinberger; 21. Strange particles William Chinowsky; 22. Strange particles: production by Cosmotron beams as observed in diffusion cloud chambers William B. Fowler; 23. From the 1940s into the 1950s Abraham Pais; Part VI. Detection of the
Double pion photoproduction off {sup 40}Ca
Energy Technology Data Exchange (ETDEWEB)
Bloch, F.; Kotulla, M.; Krusche, B. [University of Basel, Department of Physics and Astronomy, Basel (Switzerland); Ahrens, J.; Beck, R.; Hornidge, D.; Rost, M.; Thomas, A. [Johannes-Gutenberg-Universitaet Mainz, Institut fuer Kernphysik, Mainz (Germany); Annand, J.R.M.; Fog, L.S.; McGeorge, J.C.; MacGregor, I.J.D.; Owens, R.O.; Sanderson, R.; Watts, D.P. [University of Glasgow, Department of Physics and Astronomy, Glasgow (United Kingdom); Janssen, S.; Messchendorp, J.G.; Metag, V.; Novotny, R.; Pfeiffer, M.; Schadmand, S. [Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany)
2007-05-15
The photoproduction of {pi} {sup 0} {pi} {sup 0} and {pi} {sup 0} {pi} {sup {+-}} pairs off {sup 40}Ca has been investigated with the TAPS detector using the Glasgow photon tagging spectrometer at the Mainz MAMI accelerator. Data have been taken for incident photon energies in the energy range from 200-820 MeV. Total cross-sections have been extracted from threshold up to the maximum photon energy and invariant-mass distributions of the pion pairs have been obtained for incident photon energies between 400-500 MeV and 500-550 MeV. The double {pi} {sup 0} invariant-mass distributions show some relative enhancement with respect to the mixed charge channel at small invariant masses. The effects are smaller than previously observed for lead nuclei and the distributions do not significantly deviate from carbon data. The data are in good agreement with the results of recent calculations in the framework of the BUU model, with careful treatment of final-state interaction effects but without an explicit in-medium modification of scalar, iso-scalar pion pairs. This means that for Ca most of the experimentally observed effect can be explained by final-state interactions. Only at low incident photon energies there is still a small low mass enhancement of the double {pi} {sup 0} data over the BUU results. (orig.)
Role of pion pole in hard exlusive meson leptoproduction
Goloskokov, Sergey
2015-01-01
We consider the pion pole contribution and transversity effects determined by the $H_T$ and $\\bar E_T$ Generalized Parton Distributions (GPDs) which are essential in hard pseudoscalar and vector meson leptoproduction. We investigate spin effects in the $\\omega$ and $\\rho^0$ reactions. It is shown that the pion pole contribution is very important in the $\\omega$ production. Such effects in the $\\rho^0$ channel are much smaller. Our results on spin asymmetries and spin density matrix elements in these reactions were found to be in good agreement with HERMES data.
Low Energy Analyzing Powers in Pion-Proton Elastic Scattering
Meier, R; Bilger, R; Van den Brandt, B; Breitschopf, J; Clement, H; Comfort, J R; Denz, H; Erhardt, A; Föhl, K; Friedman, E; Gr"ater, J; Hautle, P; Hofman, G J; Konter, J A; Mango, S; P"atzold, J; Pavan, M M; Wagner, G J; Von Wrochem, F
2004-01-01
Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.
Inclusive and pion production neutrino-nucleus cross sections
Martini, M
2014-01-01
We analyze the experimental data on the inclusive double differential cross section by neutrinos charged current, measured by T2K, with the same model which was successful for the MiniBooNE quasielastic cross sections. As in our previous analysis the multinucleon component is needed in order to reproduce the data. For the total cross section our evaluation is smaller than the SciBooNE data above 1 GeV. This indicates the opening of a new channel not included in our evaluation, presumably the two pion emission channel. We also check that our description holds for the exclusive single pion production channel by confronting our evaluation with the MiniBooNE double differential cross section for a single charged pion and the Q^2 distribution. Both are compatible with data.
Low energy analyzing powers in pion-proton elastic scattering
Meier, R.; Cröni, M.; Bilger, R.; van den Brandt, B.; Breitschopf, J.; Clement, H.; Comfort, J. R.; Denz, H.; Erhardt, A.; Föhl, K.; Friedman, E.; Gräter, J.; Hautle, P.; Hofman, G. J.; Konter, J. A.; Mango, S.; Pätzold, J.; Pavan, M. M.; Wagner, G. J.; von Wrochem, F.
2004-05-01
Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for π-p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.
Scrutinizing the pion condensed phase
Energy Technology Data Exchange (ETDEWEB)
Carignano, Stefano; Mammarella, Andrea; Mannarelli, Massimo [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Lepori, Luca [Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); Universita dell' Aquila, Dipartimento di Scienze Fisiche e Chimiche, Coppito-L' Aquila (Italy); Pagliaroli, Giulia [INFN, Laboratori Nazionali del Gran Sasso, Assergi (Italy); Gran Sasso Science Institute, L' Aquila (Italy)
2017-02-15
When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to that of quantum magnets. By integrating out the ''radial'' fluctuations we obtain a soft Lagrangian in terms of the Nambu-Goldstone bosons arising from the breaking of the pion number symmetry. Finally, we test the robustness of the second-order transition between the normal and the pion condensed phase when next-to-leading-order chiral corrections are included. We determine the range of parameters for turning the second-order phase transition into a first-order one, finding that the currently accepted values of these corrections are unlikely to change the order of the phase transition. (orig.)
Surovtsev, Yu S; Gutsche, T; Kamiński, R; Lyubovitskij, V E; Nagy, M
2016-01-01
The basic shape of di-pion mass spectra in the two-pion transitions of both charmonia and bottomonia states is explained by an unified mechanism based on contributions of the $\\pi\\pi$, $K\\overline{K}$ and $\\eta\\eta$ coupled channels including their interference. The role of the individual $f_0$ resonances in shaping the di-pion mass distributions in the charmonia and bottomonia decays is considered.
Neutral pion number fluctuations at high multiplicity in pp-interactions at 50 GeV
Directory of Open Access Journals (Sweden)
Popov V. V.
2012-12-01
Full Text Available The results of E-190 experiment (project Thermalization with 50 GeV proton beam irradiation of SVD-2 setup are presented. MC simulation has shown the linear dependence of number of photons detected in electromagnetic calorimeter and the average number of neutral pions. Multiplicity distribution of neutral pion, N0, for total number of particles in the event, Ntot = Nch + N0, are obtained with corrections on the setup acceptance, triggering and efficiency of the event reconstruction. The scaled variance of neutral pion fluctuations, ω = D/ , versus total multiplicity is measured. The fluctuations increase at Ntot > 18. According to quantum statistics models this behavior can indicate a pion condensate formation in the high pion multiplicity system. This effect has been observed for the first time.
Pion-induced pion production on deuterium: a quasifree process
Sossi, V.; Iqbal, M. J.; Johnson, R. R.; Jones, G.; Pavan, M.; Rozon, F. M.; Sevior, M.; Vetterli, D.; Weber, P.; Sheffer, G.; Smith, G. R.; Camerini, P.; Grion, N.; Rui, R.; Stevenson, N. R.; Vicente-Vacas, M. J.
1992-10-01
A detailed experimental analysis of the π+d → π+π-pp in-plane coincidence data first presented by Rui et al. is compared to an expanded version of the Oset and Vicente-Vacas model for pion-induced pion production on a free nucleon. This extended model averages over Fermi motion to describe the assumed quasifree nature of the process occurring on the deuteron and includes nine additional diagrams to account for the N∗ → N(ππ) p-wave reaction channels. Experimental effects such as pion energy loss in the target and in the detectors, pion decay and muon detection are investigated and incorporated into the comparison of experimental data and theory. Inclusion of Fermi motion was found to be essential to provide good agreement between data and model confirming the quasifree nature of the reaction. When compared to the total-cross-section measurements of Manley et al., the free-reaction model yields a model-dependent estimate of the overall strength of the diagram containing the N∗ → N(ππ) s-wave vertex.
Pion inelastic scattering from sup 20 Ne
Energy Technology Data Exchange (ETDEWEB)
Burlein, M. (Pennsylvania Univ., Philadelphia, PA (USA). Dept. of Physics)
1989-12-01
Angular distributions for {sup 20}Ne({pi}{sup {plus minus}}, {pi}{sup {plus minus}}{prime}) were measured on the Energetic Pion Channel and Spectrometer (EPICS) at the Clinton P. Anderson Meson Physics Facility (LAMPF). Data were taken with both {pi}{sup {plus}} and {pi}{sup {minus}} over an angular range of 12{degree} to 90{degree} for T{sub {pi}}=180 MeV and with {pi}{sup +} from 15{degree} to 90{degree} for T{sub {pi}}=120 MeV. The data were analyzed using both the distorted-wave impulse approximation (DWIA) and the coupled-channels impulse approximation (CCIA) with collective transition densities. In addition, microscopic transition densities were used in the DWIA analysis for states in the lowest rotational bands. The transitions to the 6.73-MeV 0{sup +} and several 1{sup {minus}} states, including the states at 5.79 MeV and 8.71 MeV, were studied using several models for the transition density. Strong evidence for the importance of two-step routes in pion inelastic scattering was seen in several angular distributions, including the 5.79-MeV 1{sup {minus}}, the first three 4{sup +} states, and the 8.78-MeV 6{sup +}. 100 refs., 81 figs., 33 tabs.
Pion electro-production in the Roper region in chiral quark models
Golli, B; Fiolhais, M
2009-01-01
We present a method to calculate pion electro-production amplitudes in a coupled-channel framework incorporating quasi-bound quark-model states. The method offers a clear prescription how to extract the resonant part of the amplitudes, even in the presence of different decay channels and a strong mixing of neighbouring resonances. The method is applied to the calculation of the M1- and the S1- amplitudes in the P11 partial wave in a simple chiral quark model. A good agreement with the observed M1- amplitude is found with a significant contribution from the pion cloud. The same effect is also prominent in the S1- amplitude but a rather uncertain data prevent us to draw a definitive conclusion.
Energy Technology Data Exchange (ETDEWEB)
Hristova, I.
2007-12-15
.04}(syst). As a function of t', the measured values of this amplitude increase as {radical}(-t') and at larger vertical stroke t' vertical stroke the corrected ones approach the prediction, however, within their large statistical uncertainties. The phenomenology of hard exclusive electroproduction of pions is explained at present in terms of the so called QCD factorisation theorem: the amplitude for the cross section is given as a convolution of a hard scattering part calculable in perturbative quantum chromodynamics, a distribution amplitude describing the pion, and generalised parton distributions that parameterise the complex structure of the proton. Using QCD factorisation and models for the particles' structure, the value of the leading amplitude A{sup sin({phi}-{phi}{sub S})}{sub UT} is predicted to be of order unity. Although our results appear to support this prediction, a direct and more precise data-to-theory comparison requires larger statistics and improved detector capabilities than available for the present measurement. (orig.)
Dynamical Model of Weak Pion Production Reactions
Sato, T; Lee, T S H
2003-01-01
The dynamical model of pion electroproduction has been extended to investigate the weak pion production reactions. The predicted cross sections of neutrino-induced pion production reactions are in good agreement with the existing data. We show that the renormalized(dressed) axial N-$\\Delta$ form factor contains large dynamical pion cloud effects and this renormalization effects are crucial in getting agreement with the data. We conclude that the N-$\\Delta$ transitions predicted by the constituent quark model are consistent with the existing neutrino induced pion production data in the $\\Delta$ region.
Dynamical coupled-channels model study of pion photoproduction
Huang, F; Haberzettl, H; Haidenbauer, J; Hanhart, C; Krewald, S; ner, U -G Meiß; Nakayama, K
2011-01-01
The photoproduction of pion off nucleon is investigated within a dynamical coupled-channels approach based on the Juelich pi-N model, which has been quite successful in the description of pi-N to pi-N scattering for center-of-mass energies up to 1.9 GeV. The full pion photoproduction amplitude is constructed to satisfy the generalized Ward-Takahashi identity and hence, it is fully gauge invariant. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions gamma p to pi^+ n, gamma p to pi^0 p and gamma n to pi^- p are in good agreement with the experimental data.
Scrutinizing the pion condensed phase
Carignano, Stefano; Mammarella, Andrea; Mannarelli, Massimo; Pagliaroli, Giulia
2016-01-01
When the isospin chemical potential exceeds the pion mass, charged pions condense in the zero-momentum state forming a superfluid. Chiral perturbation theory provides a very powerful tool for studying this phase. However, the formalism that is usually employed in this context does not clarify various aspects of the condensation mechanism and makes the identification of the soft modes problematic. We re-examine the pion condensed phase using different approaches within the chiral perturbation theory framework. As a first step, we perform a low-density expansion of the chiral Lagrangian valid in the normal phase and close to the onset of the Bose-Einstein condensation. We obtain an effective theory that can be mapped to a Gross-Pitaevskii Lagrangian in which, remarkably, all the coefficients depend on the isospin chemical potential. The low-density expansion becomes unreliable deep in the pion condensed phase. For this reason, we develop an alternative field expansion deriving a low-energy Lagrangian analog to ...
Total cross sections for pion charge exchange on the proton
Energy Technology Data Exchange (ETDEWEB)
Breitschopf, J.
2006-04-28
This work describes the measurement of total SCX cross sections employing a new 4{pi} scintillation counter to perform transmission measurements in the incident pion energy range from about 38 to 250 MeV. A small 4{pi} detector box consisting of thin plastic scintillators has been constructed. The transmission technique, which was used, relates the number of transmitted charged pions to that of incident beam pions and this way effectively counts events with neutral products. The incoming negative pions were counted by three beam defining counters before they hit a target of very well known size and chemical composition. The target was placed in the box detector which was not sensitive to the neutral particles resulting from the SCX. The total cross section for emerging neutral particles was derived from the comparison of the numbers of the incoming and transmitted charged particles. The total SCX cross section on hydrogen was derived from the transmissions of a CH{sub 2} target, a carbon target and an empty target. For a detailed offline analysis all TDC, QDC and FADC information was recorded in an event by event mode for each triggered beam event. Various corrections had to be applied to the data, such as random correction, the detection of neutrals in the detector, Dalitz decay, pion decay and the radiative pion capture. This measurement covers, as the only experiment, the whole {delta}-resonance and the sp-interference region in one single experimental setup and improves the available data base for the SCX reaction. It is shown that the description of the SCX cross sections is improved if the s-wave amplitudes, that have been fixed essentially by elastic pion-nucleon scattering data, is reduced by (4{+-}1.5)%. The exact value depends on the SCX literature data included and on the parameters of the {delta}{sup 0} Breit-Wigner resonance describing the p{sub 33}-waves. This shows that p-wave as well as s-wave effects should be considered in studies of isospin
Subthreshold Production of Neutral Pions in Heavy Ion Collisions
2002-01-01
The pion production below the threshold at 290 MeV/u (corresponding to the minimum beam velocity at which pions can be produced in nucleon-nucleon collisions) is sensitive to coherent effects in the momentum distribution of the nucleons in the internuclear collision region. Such collective or coherent effects would manifest themselves in an enhancement of the observed cross section with respect to a prediction on the basis of model momentum distributions, e.g. from the Fermi gas model. \\\\ \\\\ With neutral pions such experiments can be extended to rather low energies and rather small cross sections (in the sub-@mb range) due to the fact that the @p|0's leave the composite nuclear system undisturbed by the Coulomb forces and that their decay $\\gamma$ rays can be detected with high efficiency also at very low pion momentum. In our experiments using |1|2C~ions of 60, 74 and 84~MeV/u and |1|80 of 84~MeV/u we were able to clearly sep from background from different sources. The large efficiency of the annular lead gl...
Measurement of the Azimuthal Anisotropy of Neutral Pions in Pb-Pb Collisions at sNN=2.76TeV
Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Aguilo, E.; Bergauer, T.; Dragicevic, M.; Erö, J.; Fabjan, C.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hammer, J.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knünz, V.; Krammer, M.; Krätschmer, I.; Liko, D.; Mikulec, I.; Pernicka, M.; Rahbaran, B.; Rohringer, C.; Rohringer, H.; Schöfbeck, R.; Strauss, J.; Taurok, A.; Waltenberger, W.; Walzel, G.; Widl, E.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Bansal, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Luyckx, S.; Mucibello, L.; Ochesanu, S.; Roland, B.; Rougny, R.; Selvaggi, M.; Staykova, Z.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Blekman, F.; Blyweert, S.; D'Hondt, J.; Gonzalez Suarez, R.; Kalogeropoulos, A.; Maes, M.; Olbrechts, A.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Villella, I.; Clerbaux, B.; De Lentdecker, G.; Dero, V.; Gay, A. P. R.; Hreus, T.; Léonard, A.; Marage, P. E.; Reis, T.; Thomas, L.; Vander Marcken, G.; Vander Velde, C.; Vanlaer, P.; Wang, J.; Adler, V.; Beernaert, K.; Cimmino, A.; Costantini, S.; Garcia, G.; Grunewald, M.; Klein, B.; Lellouch, J.; Marinov, A.; Mccartin, J.; Ocampo Rios, A. A.; Ryckbosch, D.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Verwilligen, P.; Walsh, S.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Bruno, G.; Castello, R.; Ceard, L.; Delaere, C.; du Pree, T.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Lemaitre, V.; Liao, J.; Militaru, O.; Nuttens, C.; Pagano, D.; Pin, A.; Piotrzkowski, K.; Schul, N.; Vizan Garcia, J. M.; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Alves, G. A.; Correa Martins Junior, M.; De Jesus Damiao, D.; Martins, T.; Pol, M. E.; Souza, M. H. G.; Aldá Júnior, W. L.; Carvalho, W.; Custódio, A.; Da Costa, E. M.; De Oliveira Martins, C.; Fonseca De Souza, S.; Matos Figueiredo, D.; Mundim, L.; Nogima, H.; Oguri, V.; Prado Da Silva, W. L.; Santoro, A.; Soares Jorge, L.; Sznajder, A.; Anjos, T. S.; Bernardes, C. A.; Dias, F. A.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Lagana, C.; Marinho, F.; Mercadante, P. G.; Novaes, S. F.; Padula, Sandra S.; Genchev, V.; Iaydjiev, P.; Piperov, S.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Tcholakov, V.; Trayanov, R.; Vutova, M.; Dimitrov, A.; Hadjiiska, R.; Kozhuharov, V.; Litov, L.; Pavlov, B.; Petkov, P.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Jiang, C. H.; Liang, D.; Liang, S.; Meng, X.; Tao, J.; Wang, J.; Wang, X.; Wang, Z.; Xiao, H.; Xu, M.; Zang, J.; Zhang, Z.; Asawatangtrakuldee, C.; Ban, Y.; Guo, S.; Guo, Y.; Li, W.; Liu, S.; Mao, Y.; Qian, S. J.; Teng, H.; Wang, D.; Zhang, L.; Zhu, B.; Zou, W.; Avila, C.; Gomez, J. P.; Gomez Moreno, B.; Osorio Oliveros, A. F.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Plestina, R.; Polic, D.; Puljak, I.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Duric, S.; Kadija, K.; Luetic, J.; Morovic, S.; Attikis, A.; Galanti, M.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Finger, M.; Finger, M., Jr.; Assran, Y.; Elgammal, S.; Ellithi Kamel, A.; Khalil, S.; Mahmoud, M. A.; Radi, A.; Kadastik, M.; Müntel, M.; Raidal, M.; Rebane, L.; Tiko, A.; Eerola, P.; Fedi, G.; Voutilainen, M.; Härkönen, J.; Heikkinen, A.; Karimäki, V.; Kinnunen, R.; Kortelainen, M. J.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Ungaro, D.; Wendland, L.; Banzuzi, K.; Karjalainen, A.; Korpela, A.; Tuuva, T.; Besancon, M.; Choudhury, S.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Malcles, J.; Millischer, L.; Nayak, A.; Rander, J.; Rosowsky, A.; Shreyber, I.; Titov, M.; Baffioni, S.; Beaudette, F.; Benhabib, L.; Bianchini, L.; Bluj, M.; Broutin, C.; Busson, P.; Charlot, C.; Daci, N.; Dahms, T.; Dobrzynski, L.; Granier de Cassagnac, R.; Haguenauer, M.; Miné, P.; Mironov, C.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Paganini, P.; Sabes, D.; Salerno, R.; Sirois, Y.; Veelken, C.; Zabi, A.; Agram, J.-L.; Andrea, J.; Bloch, D.; Bodin, D.; Brom, J.-M.; Cardaci, M.; Chabert, E. C.; Collard, C.; Conte, E.; Drouhin, F.; Ferro, C.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Juillot, P.; Le Bihan, A.-C.; Van Hove, P.; Fassi, F.; Mercier, D.; Beauceron, S.; Beaupere, N.; Bondu, O.; Boudoul, G.; Chasserat, J.; Chierici, R.; Contardo, D.; Depasse, P.; El Mamouni, H.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Kurca, T.; Lethuillier, M.; Mirabito, L.; Perries, S.; Sordini, V.; Tschudi, Y.; Verdier, P.; Viret, S.; Tsamalaidze, Z.; Anagnostou, G.; Beranek, S.; Edelhoff, M.; Feld, L.; Heracleous, N.; Hindrichs, O.; Jussen, R.; Klein, K.; Merz, J.; Ostapchuk, A.
2013-01-01
First measurements of the azimuthal anisotropy of neutral pions produced in Pb-Pb collisions at a center-of-mass energy of sNN=2.76TeV are presented. The amplitudes of the second Fourier component (v2) of the π0 azimuthal distributions are extracted using an event-plane technique. The values of v2 are studied as a function of the neutral pion transverse momentum (pT) for different classes of collision centrality in the kinematic range 1.6
Chatrchyan, S; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Adam, W; Aguilo, E; Bergauer, T; Dragicevic, M; Erö, J; Fabjan, C; Friedl, M; Frühwirth, R; Ghete, V M; Hammer, J; Hörmann, N; Hrubec, J; Jeitler, M; Kiesenhofer, W; Knünz, V; Krammer, M; Krätschmer, I; Liko, D; Mikulec, I; Pernicka, M; Rahbaran, B; Rohringer, C; Rohringer, H; Schöfbeck, R; Strauss, J; Taurok, A; Waltenberger, W; Walzel, G; Widl, E; Wulz, C-E; Mossolov, V; Shumeiko, N; Suarez Gonzalez, J; Bansal, S; Cornelis, T; De Wolf, E A; Janssen, X; Luyckx, S; Mucibello, L; Ochesanu, S; Roland, B; Rougny, R; Selvaggi, M; Staykova, Z; Van Haevermaet, H; Van Mechelen, P; Van Remortel, N; Van Spilbeeck, A; Blekman, F; Blyweert, S; D'Hondt, J; Gonzalez Suarez, R; Kalogeropoulos, A; Maes, M; Olbrechts, A; Van Doninck, W; Van Mulders, P; Van Onsem, G P; Villella, I; Clerbaux, B; De Lentdecker, G; Dero, V; Gay, A P R; Hreus, T; Léonard, A; Marage, P E; Reis, T; Thomas, L; Vander Marcken, G; Vander Velde, C; Vanlaer, P; Wang, J; Adler, V; Beernaert, K; Cimmino, A; Costantini, S; Garcia, G; Grunewald, M; Klein, B; Lellouch, J; Marinov, A; Mccartin, J; Ocampo Rios, A A; Ryckbosch, D; Strobbe, N; Thyssen, F; Tytgat, M; Verwilligen, P; Walsh, S; Yazgan, E; Zaganidis, N; Basegmez, S; Bruno, G; Castello, R; Ceard, L; Delaere, C; du Pree, T; Favart, D; Forthomme, L; Giammanco, A; Hollar, J; Lemaitre, V; Liao, J; Militaru, O; Nuttens, C; Pagano, D; Pin, A; Piotrzkowski, K; Schul, N; Vizan Garcia, J M; Beliy, N; Caebergs, T; Daubie, E; Hammad, G H; Alves, G A; Correa Martins Junior, M; De Jesus Damiao, D; Martins, T; Pol, M E; Souza, M H G; Aldá Júnior, W L; Carvalho, W; Custódio, A; Da Costa, E M; De Oliveira Martins, C; Fonseca De Souza, S; Matos Figueiredo, D; Mundim, L; Nogima, H; Oguri, V; Prado Da Silva, W L; Santoro, A; Soares Jorge, L; Sznajder, A; Anjos, T S; Bernardes, C A; Dias, F A; Fernandez Perez Tomei, T R; Gregores, E M; Lagana, C; Marinho, F; Mercadante, P G; Novaes, S F; Padula, Sandra S; Genchev, V; Iaydjiev, P; Piperov, S; Rodozov, M; Stoykova, S; Sultanov, G; Tcholakov, V; Trayanov, R; Vutova, M; Dimitrov, A; Hadjiiska, R; Kozhuharov, V; Litov, L; Pavlov, B; Petkov, P; Bian, J G; Chen, G M; Chen, H S; Jiang, C H; Liang, D; Liang, S; Meng, X; Tao, J; Wang, J; Wang, X; Wang, Z; Xiao, H; Xu, M; Zang, J; Zhang, Z; Asawatangtrakuldee, C; Ban, Y; Guo, S; Guo, Y; Li, W; Liu, S; Mao, Y; Qian, S J; Teng, H; Wang, D; Zhang, L; Zhu, B; Zou, W; Avila, C; Gomez, J P; Gomez Moreno, B; Osorio Oliveros, A F; Sanabria, J C; Godinovic, N; Lelas, D; Plestina, R; Polic, D; Puljak, I; Antunovic, Z; Kovac, M; Brigljevic, V; Duric, S; Kadija, K; Luetic, J; Morovic, S; Attikis, A; Galanti, M; Mavromanolakis, G; Mousa, J; Nicolaou, C; Ptochos, F; Razis, P A; Finger, M; Finger, M; Assran, Y; Elgammal, S; Ellithi Kamel, A; Khalil, S; Mahmoud, M A; Radi, A; Kadastik, M; Müntel, M; Raidal, M; Rebane, L; Tiko, A; Eerola, P; Fedi, G; Voutilainen, M; Härkönen, J; Heikkinen, A; Karimäki, V; Kinnunen, R; Kortelainen, M J; Lampén, T; Lassila-Perini, K; Lehti, S; Lindén, T; Luukka, P; Mäenpää, T; Peltola, T; Tuominen, E; Tuominiemi, J; Tuovinen, E; Ungaro, D; Wendland, L; Banzuzi, K; Karjalainen, A; Korpela, A; Tuuva, T; Besancon, M; Choudhury, S; Dejardin, M; Denegri, D; Fabbro, B; Faure, J L; Ferri, F; Ganjour, S; Givernaud, A; Gras, P; Hamel de Monchenault, G; Jarry, P; Locci, E; Malcles, J; Millischer, L; Nayak, A; Rander, J; Rosowsky, A; Shreyber, I; Titov, M; Baffioni, S; Beaudette, F; Benhabib, L; Bianchini, L; Bluj, M; Broutin, C; Busson, P; Charlot, C; Daci, N; Dahms, T; Dobrzynski, L; Granier de Cassagnac, R; Haguenauer, M; Miné, P; Mironov, C; Naranjo, I N; Nguyen, M; Ochando, C; Paganini, P; Sabes, D; Salerno, R; Sirois, Y; Veelken, C; Zabi, A; Agram, J-L; Andrea, J; Bloch, D; Bodin, D; Brom, J-M; Cardaci, M; Chabert, E C; Collard, C; Conte, E; Drouhin, F; Ferro, C; Fontaine, J-C; Gelé, D; Goerlach, U; Juillot, P; Le Bihan, A-C; Van Hove, P; Fassi, F; Mercier, D; Beauceron, S; Beaupere, N; Bondu, O; Boudoul, G; Chasserat, J; Chierici, R; Contardo, D; Depasse, P; El Mamouni, H; Fay, J; Gascon, S; Gouzevitch, M; Ille, B; Kurca, T; Lethuillier, M; Mirabito, L; Perries, S; Sordini, V; Tschudi, Y; Verdier, P; Viret, S; Tsamalaidze, Z; Anagnostou, G; Beranek, S; Edelhoff, M; Feld, L; Heracleous, N; Hindrichs, O; Jussen, R; Klein, K; Merz, J; Ostapchuk, A; Perieanu, A; Raupach, F; Sammet, J; Schael, S; Sprenger, D; Weber, H; Wittmer, B; Zhukov, V; Ata, M; Caudron, J; Dietz-Laursonn, E; Duchardt, D; Erdmann, M; Fischer, R; Güth, A; Hebbeker, T; Heidemann, C; Hoepfner, K; Klingebiel, D; Kreuzer, P; Magass, C; Merschmeyer, M; Meyer, A; Olschewski, M; Papacz, P; Pieta, H; Reithler, H; Schmitz, S A; Sonnenschein, L; Steggemann, J; Teyssier, D; Weber, M; Bontenackels, M; Cherepanov, V; Flügge, G; Geenen, H; Geisler, M
2013-01-25
First measurements of the azimuthal anisotropy of neutral pions produced in Pb-Pb collisions at a center-of-mass energy of sqrt[s(NN)] = 2.76 TeV are presented. The amplitudes of the second Fourier component (v(2)) of the π(0) azimuthal distributions are extracted using an event-plane technique. The values of v(2) are studied as a function of the neutral pion transverse momentum (p(T)) for different classes of collision centrality in the kinematic range 1.6
pion anisotropies are found to be smaller than those observed by CMS for inclusive charged particles.
Threshold pion production in proton-proton collisions at NNLO in chiral EFT
Baru, V.; Epelbaum, E.; Filin, A. A.; Hanhart, C.; Krebs, H.; Myhrer, F.
2016-05-01
The reaction NN → NN π offers a good testing ground for chiral effective field theory at intermediate energies. It challenges our understanding of the first inelastic channel in nucleon-nucleon scattering and of the charge symmetry breaking pattern in hadronic reactions. In our previous studies, we presented a complete calculation of the pion production operator for s -wave pions up-to-and-including next-to-next-to-leading order (NNLO) in the formulation of chiral effective field theory, which includes pions, nucleons and Δ(1232) degrees of freedom. In this paper we calculate the near-threshold cross section for the pp → d π+ reaction by performing the convolution of the obtained operators with nuclear wave functions based on modern phenomenological and chiral potentials. The available chiral NN wave functions are constructed with a cutoff comparable with the momentum transfer scale inherent in pion production reactions. Hence, a significant portion of the dynamical intermediate-range physics is thereby cut off by them. On the other hand, the NNLO amplitudes evaluated with phenomenological wave functions appear to be largely independent of the NN model used and give corrections to the dominant leading-order contributions as expected from dimensional analysis. The result gives support to the counting scheme used to classify the pion production operators, which is a precondition for a reliable investigation of the chirally suppressed neutral pion production. The explicit inclusion of the Δ(1232) is found to be important but smaller than expected due to cancellations.
Mikhailov, S V; Stefanis, N G
2016-01-01
We consider the pion-photon transition form factor at low to intermediate spacelike momenta within the theoretical framework of light-cone sum rules. We derive predictions which take into account all currently known contributions stemming from QCD perturbation theory up to the next-to-next-to-leading order (NNLO) and by including all twist terms up to order six. In order to enable a more detailed comparison with forthcoming high-precision data, we also estimate the main systematic theoretical uncertainties, stemming from various sources, and discuss their influence on the calculations --- in particular the dominant one related to the still uncalculated part of the NNLO contribution. The analysis addresses, in broad terms, also the role of the twist-two pion distribution amplitude derived with different approaches.
Three pion nucleon coupling constants
Arriola, E Ruiz; Perez, R Navarro
2016-01-01
There exist four pion nucleon coupling constants, $f_{\\pi^0, pp}$, $-f_{\\pi^0, nn}$, $f_{\\pi^+, pn} /\\sqrt{2}$ and $ f_{\\pi^-, np} /\\sqrt{2}$ which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination $$f_p^2 = 0.0759(4) \\, , \\quad f_{0}^2 = 0.079(1) \\,, \\quad f_{c}^2 = 0.0763(6) \\, , $$ based on a partial wave analysis of the $3\\sigma$ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.
Renormalization of the Off-shell chiral two-pion exchange NN interactions
Entem, D R
2009-01-01
The renormalization, finiteness and off-shellness of short distance power like singular interactions is discussed. We show analytically that the renormalizability of the off-shell scattering amplitude relies completely on the corresponding on-shell amplitude without proliferation of new counterterms. We illustrate the result by complementary calculations both in coordinate as well as in momentum space in the simplest 1S0 channel for chiral np interactions including Two Pion Exchange.
Two-meson and multi-pion final states from 600 gev pion interactions
Moinester, M A
1994-01-01
This report describes the transitions pion ---> meson_1 + meson_2 and also pion ----> multi-pion for high energy pions interacting with target nuclei (Z,A). The physics interests are: A) Nuclear inelastic coherent diffraction cross sections for pions, for studies of size fluctuations in the pion wave function. B) Radiative widths of excited meson states, for tests of vector dominance and quark models. C) Experimental determination of the pi- + rho -----> pi- + gamma total reaction rate for gamma production above 0.7 GeV, needed for background studies of quark-gluon plasma formation experiments. D) Investigation of the gamma ---->3 pi vertex in pion pair production by a pion, for a significantly improved test of the hypothesis of chiral anomalies. The physics interest and associated bibliography are summarized here; with particular reference to the 200-600 GeV beams available at FNAL and CERN. Complementary GEANT simulations and trigger studies are needed.
How strange is pion electroproduction?
Gorchtein, Mikhail; Zhang, Xilin
2015-01-01
We consider pion production in parity-violating electron scattering (PVES) in the presence of nucleon strangeness in the framework of partial wave analysis with unitarity. Using the experimental bounds on the strange form factors obtained in elastic PVES, we study the sensitivity of the parity-violating asymmetry to strange nucleon form factors. For forward kinematics and electron energies above 1 GeV, we observe that this sensitivity may reach about 20\\% in the threshold region. With parity-violating asymmetries being as large as tens p.p.m., this study suggests that threshold pion production in PVES can be used as a promising way to better constrain strangeness contributions. Using this model for the neutral current pion production, we update the estimate for the dispersive $\\gamma Z$-box correction to the weak charge of the proton. In the kinematics of the Qweak experiment, our new prediction reads Re$\\,\\Box_{\\gamma Z}^V(E=1.165\\,{\\rm GeV}) = (5.58\\pm1.41)\\times10^{-3}$, an improvement over the previous un...
Anomalies Dismissed of Ambiguities and the Neutral Pion Decay
Battistel, O A
2002-01-01
The correlation between the neutral electromagnetic pion decay, the Sutherland-Veltman paradox and the $AVV$ triangle anomaly phenomenon is discussed within the framework of an alternative strategy to handle the divergences involved in the perturbative evaluation of the associated physical amplitudes. We show that the general characteristic of the adopted strategy allows us to recover the traditional treatment for the problem as well as allows us to construct an alternative way to look at the problem where the ambiguities play no relevant role.
Anomalies dismissed of ambiguities and the neutral pion decay
Energy Technology Data Exchange (ETDEWEB)
Battistel, O.A. [Department of Physics-CCNE, Universidade Federal de Santa Maria, Santa Maria, RS (Brazil)]. E-mail: orimar@ccne.ufsm.br; Dallabona, G. [Department of Physics-ICEx, Universidade Federal de Minas Gerais, Belo Horizonte (Brazil)]. E-mail: dalla@fisica.ufmg.br
2002-10-01
The correlation between the neutral electromagnetic pion decay, the Sutherland-Veltman paradox and the AVV triangle anomaly phenomenon is discussed within the framework of an alternative strategy to handle the divergences involved in the perturbative evaluation of the associated physical amplitudes. We show that the general characteristic of the adopted strategy allows us to recover the traditional treatment for the problem as well as allowing us to construct an alternative way to look at the problem where the ambiguities play no relevant role. (author)
Pion production in neutrino-nucleus collisions
Hernández, E; Vacas, M J Vicente
2013-01-01
We compare our pion production results with recent MiniBooNE data measured in mineral oil. Our total cross sections lie below experimental data for neutrino energies above 1 GeV. Differential cross sections show our model produces too few high energy pions in the forward direction as compared to data. The agreement with experiment improves by artificially removing pion final state interaction.
Experimental study of rare charged pion decays
Pocanic, Dinko; van der Schaaf, Andries
2014-01-01
The combination of simple dynamics, small number of available decay channels, and extremely well controlled radiative and loop corrections, make charged pion decays a sensitive means for testing the underlying symmetries and the universality of weak fermion couplings, as well as for improving our understanding of pion structure and chiral dynamics. This paper reviews the current state of experimental study of the allowed rare decays of charged pions: (a) leptonic, $\\pi^+ \\to e^+\
Criteria and techniques for three-dimensional treatment planning with pions
Energy Technology Data Exchange (ETDEWEB)
Berardo, P.; Zink, S.; Paciotti, M.; Bradbury, J.
1981-01-01
The ability to predict a pion dose distribution in a patient is a major objective of the clinical trials at LAMPF. Accurate predictions are essential for evaluation of pion therapy. But accuracy must be in the context of clinical utility. That is, reasonable approximations must be made in calculational methods so that treatment planning can proceed in a timely and efficient manner. A few of the techniques and current developments used to achieve that objective are presented here.
Coherent Pions From Neutrino Scattering Off Nuclei
Valverde, M; Hernandez, E; Nieves, J; Vacas, M J Vicente
2010-01-01
We describe a model for pion production off nucleons and coherent pions from nuclei induced by neutrinos in the 1 GeV energy regime. Besides the dominant Delta pole contribution, it takes into account the effect of background terms required by chiral symmetry. Moreover, the model uses a reduced nucleon-to-Delta resonance axial coupling, which leads to coherent pion production cross sections around a factor two smaller than most of the previous theoretical estimates. Nuclear effects like medium corrections on the Delta propagator and final pion distortion are included.
Takemura, Shunsuke; Kobayashi, Manabu; Yoshimoto, Kazuo
2016-10-01
Frequency-dependent model of the apparent radiation pattern has been extensively incorporated into engineering and scientific applications for high-frequency seismic waves, but distance-dependent properties have not yet been fully taken into account. We investigated the unified characteristics of frequency and distance dependences in both apparent P- and S-wave radiation patterns during local crustal earthquakes. Observed distortions of the apparent P- and S-wave radiation patterns could be simply modeled by using a function of the normalized hypocentral distance, which is a product of the wave number and hypocentral distance. This behavior suggests that major cause of distortion of the apparent radiation pattern is seismic wave scattering and diffraction within the heterogeneous crust. On the basis of observed normalized hypocentral distance dependency, we proposed a method for prediction of spatial distributions of maximum P- and S-wave amplitudes. Our method incorporating normalized hypocentral distance dependence of the apparent radiation pattern reproduced the observed spatial distributions of maximum P- and S-wave amplitudes over a wide frequency and distance ranges successfully.[Figure not available: see fulltext.
Inclusive pion - proton scattering
Energy Technology Data Exchange (ETDEWEB)
Williams, R.W.; Rothberg, J.E.; Cook, V.; Wolfe, D.M.; Young, K.K.; Schenck, A.; Sompayrac, L.; Romer, H.; /Washington U., Seattle
1970-06-01
The reactions {pi}+ p {yields} {pi}+ {hor_ellipsis} and {pi}+ p {yields} K+ {hor_ellipsis} will be studied over a wide range of the Feynman variables X, Q and S in order to test the conjectured scaling law for hadron collisions and study the form of the yield distributions. Particular attention will be paid to the vicinity of X = 0. The experiment will be carried out with a simple one-magnet spectrometer which takes full advantage of the kinematics and has wide acceptance and the capability of high precision.
Two-pion exchange nucleon-nucleon potential Model independent features
Robilotta, Manoel R.; da Rocha, Carlos A.
1997-02-01
A chiral pion-nucleon amplitude supplemented by the HJS subthreshold coefficients is used to calculate the the long range part of the two-pion exchange nucleon-nucleon potential. In our expressions the HJS coefficients factor out, allowing a clear identification of the origin of the various contributions. A discussion of the configuration space behaviour of the loop integrals that determine the potential is presented, with emphasis on cancellations associated with chiral symmetry. The profile function for the scalar-isoscalar component of the potential is produced and shown to disagree with those of several semi-phenomenological potentials.
Joo, K; Aznauryan, I G; Burkert, V D; Egiyan, H; Minehart, R C; Adams, G; Ambrozewicz, P; Anciant, E; Anghinolfi, M; Asavapibhop, B; Asryan, G; Audit, G; Auger, T; Avakian, H; Bagdasaryan, H; Baillie, N; Ball, J P; Baltzell, N A; Barrow, S; Batourine, V; Battaglieri, M; Beard, K; Bedlinskiy, I; Bektasoglu, M; Bellis, M; Benmouna, N; Berman, B L; Bianchi, N; Biselli, A S; Bonner, B E; Bouchigny, S; Boiarinov, S; Bradford, R; Branford, D; Briscoe, W J; Brooks, W K; Bültmann, S; Butuceanu, C; Calarco, J R; Careccia, S L; Carman, D S; Carnahan, B; Cetina, C; Chen, S; Cole, P L; Coleman, A; Coltharp, P; Cords, D; Corvisiero, P; Crabb, D; Cummings, J P; De Sanctis, E; De Vita, R; Degtyarenko, P V; Dennis, L; Deur, A; Dharmawardane, K V; Dhuga, K S; Djalali, C; Dodge, G E; Donnelly, J; Doughty, D; Dragovitsch, P; Dugger, M; Dytman, S; Dzyubak, O P; Egiyan, K S; Elouadrhiri, L; Empl, A; Eugenio, P; Farhi, L; Fatemi, R; Fedotov, G; Feldman, G; Feuerbach, R J; Forest, T A; Frolov, V; Funsten, H; Gaff, S J; Garçon, M; Gavalian, G; Gilfoyle, G P; Giovanetti, K L; Girard, P; Girod, F X; Goetz, J T; Gothe, R W; Griffioen, K A; Guidal, M; Guillo, M; Guler, N; Guo, L; Gyurjyan, V; Hakobyan, R S; Hardie, J; Heddle, D; Hersman, F W; Hicks, K; Hleiqawi, I; Holtrop, M; Hu, J; Hyde-Wright, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Ito, M M; Jenkins, D; Jo, H S; Jüngst, H G; Kelley, J H; Kellie, J D; Khandaker, M; Kim, K Y; Kim, K; Kim, W; Klein, A; Klein, F J; Klimenko, A V; Klusman, M; Kossov, M; Kramer, L H; Kubarovski, V; Kühn, J; Kuhn, S E; Lachniet, J; Laget, J M; Langheinrich, J; Lawrence, D; Lee, T; Livingston, K; Lukashin, K; Manak, J J; Marchand, C; Maximon, L C; McAleer, S; McKinnon, B; McNabb, J W C; Mecking, B A; Mestayer, M D; Meyer, C A; Mikhailov, K; Mirazita, M; Miskimen, R; Mokeev, V; Morrow, S A; Muccifora, V; Müller, J; Mutchler, G S; Nadel-Turonski, P; Napolitano, J; Nasseripour, R; Nelson, S O; Niccolai, S; Niculescu, G; Niculescu, I; Niczyporuk, B B; Niyazov, R A; Nozar, M; O'Rielly, G V; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Peterson, G; Philips, S A; Pierce, J; Pivnyuk, N; Pocanic, D; Pogorelko, O I; Polli, E; Pozdniakov, S; Preedom, B M; Price, J W; Prok, Y; Protopopescu, D; Qin, L M; Raue, B A; Riccardi, G; Ricco, G; Ripani, M; Ritchie, B G; Ronchetti, F; Rosner, G; Rossi, P; Rowntree, D; Rubin, P D; Sabatie, F; Sabourov, K; Salgado, C; Santoro, J P; Sapunenko, V; Schumacher, R A; Serov, V S; Shafi, A; Sharabyan, Yu G; Shaw, J; Simionatto, S; Skabelin, A V; Smith, E S; Sober, D I; Spraker, M; Stavinsky, A V; Stepanyan, S; Stokes, B E; Stoler, P; Strakovsky, I I; Strauch, S; Taiuti, M; Taylor, S; Tedeschi, D J; Thoma, U; Thompson, R; Tkabladze, A; Tur, C; Ungaro, M; Vineyard, M F; Vlassov, A V; Wang, K; Weinstein, L B; Weller, H; Weygand, D P; Williams, M; Wolin, E; Wood, M H; Yegneswaran, A; Yun, J; Zana, L; Zhang, J
2005-01-01
The polarized longitudinal-transverse structure function $\\sigma_{LT^\\prime}$ measures the interference between real and imaginary amplitudes in pion electroproduction and can be used to probe the coupling between resonant and non-resonant processes. We report new measurements of $\\sigma_{LT^\\prime}$ in the $N(1440){1/2}^+$ (Roper) resonance region at $Q^2=0.40$ and 0.65 GeV$^2$ for both the $\\pi^0 p$ and $\\pi^+ n$ channels. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at a beam energy of 1.515 GeV. Complete angular distributions were obtained and are compared to recent phenomenological models. The $\\sigma_{LT^\\prime}(\\pi^+ n)$ channel shows a large sensitivity to the Roper resonance multipoles $M_{1-}$ and $S_{1-}$ and provides new constraints on models of resonance formation.
Joo, K.; Smith, L. C.; Aznauryan, I. G.; Burkert, V. D.; Egiyan, H.; Minehart, R.; Adams, G.; Ambrozewicz, P.; Anciant, E.; Anghinolfi, M.; Asavapibhop, B.; Asryan, G.; Audit, G.; Auger, T.; Avakian, H.; Bagdasaryan, H.; Baillie, N.; Ball, J. P.; Baltzell, N. A.; Barrow, S.; Batourine, V.; Battaglieri, M.; Beard, K.; Bedlinskiy, I.; Bektasoglu, M.; Bellis, M.; Benmouna, N.; Berman, B. L.; Bianchi, N.; Biselli, A. S.; Bonner, B. E.; Bouchigny, S.; Boiarinov, S.; Bradford, R.; Branford, D.; Briscoe, W. J.; Brooks, W. K.; Bueltmann, S.; Butuceanu, C.; Calarco, J. R.; Careccia, S. L.; Carman, D. S.; Carnahan, B.; Cetina, C.; Chen, S.; Cole, P. L.; Coleman, A.; Coltharp, P.; Cords, D.; Corvisiero, P.; Crabb, D.; Cummings, J. P.; Sanctis, E. De; Devita, R.; Degtyarenko, P. V.; Dennis, L.; Deur, A.; Dharmawardane, K. V.; Dhuga, K. S.; Djalali, C.; Dodge, G. E.; Donnelly, J.; Doughty, D.; Dragovitsch, P.; Dugger, M.; Dytman, S.; Dzyubak, O. P.; Egiyan, K. S.; Elouadrhiri, L.; Empl, A.; Eugenio, P.; Farhi, L.; Fatemi, R.; Fedotov, G.; Feldman, G.; Feuerbach, R. J.; Forest, T. A.; Frolov, V.; Funsten, H.; Gaff, S. J.; Garçon, M.; Gavalian, G.; Gilfoyle, G. P.; Giovanetti, K. L.; Girard, P.; Girod, F. X.; Goetz, J. T.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guillo, M.; Guler, N.; Guo, L.; Gyurjyan, V.; Hakobyan, R. S.; Hardie, J.; Heddle, D.; Hersman, F. W.; Hicks, K.; Hleiqawi, I.; Holtrop, M.; Hu, J.; Hyde-Wright, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Ito, M. M.; Jenkins, D.; Jo, H. S.; Juengst, H. G.; Kelley, J. H.; Kellie, J. D.; Khandaker, M.; Kim, K. Y.; Kim, K.; Kim, W.; Klein, A.; Klein, F. J.; Klimenko, A. V.; Klusman, M.; Kossov, M.; Kramer, L. H.; Kubarovsky, V.; Kuhn, J.; Kuhn, S. E.; Lachniet, J.; Laget, J. M.; Langheinrich, J.; Lawrence, D.; Lee, T.; Livingston, K.; Lukashin, K.; Manak, J. J.; Marchand, C.; Maximon, L. C.; McAleer, S.; McKinnon, B.; McNabb, J. W.; Mecking, B. A.; Mestayer, M. D.; Meyer, C. A.; Mikhailov, K.; Mirazita, M.; Miskimen, R.; Mokeev, V.; Morrow, S. A.; Muccifora, V.; Mueller, J.; Mutchler, G. S.; Nadel-Turonski, P.; Napolitano, J.; Nasseripour, R.; Nelson, S. O.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Niczyporuk, B. B.; Niyazov, R. A.; Nozar, M.; O'Rielly, G. V.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Peterson, G.; Philips, S. A.; Pierce, J.; Pivnyuk, N.; Pocanic, D.; Pogorelko, O.; Polli, E.; Pozdniakov, S.; Preedom, B. M.; Price, J. W.; Prok, Y.; Protopopescu, D.; Qin, L. M.; Raue, B. A.; Riccardi, G.; Ricco, G.; Ripani, M.; Ritchie, B. G.; Ronchetti, F.; Rosner, G.; Rossi, P.; Rowntree, D.; Rubin, P. D.; Sabatié, F.; Sabourov, K.; Salgado, C.; Santoro, J. P.; Sapunenko, V.; Schumacher, R. A.; Serov, V. S.; Shafi, A.; Sharabian, Y. G.; Shaw, J.; Simionatto, S.; Skabelin, A. V.; Smith, E. S.; Sober, D. I.; Spraker, M.; Stavinsky, A.; Stepanyan, S. S.; Stepanyan, S.; Stokes, B. E.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Taylor, S.; Tedeschi, D. J.; Thoma, U.; Thompson, R.; Tkabladze, A.; Tur, C.; Ungaro, M.; Vineyard, M. F.; Vlassov, A. V.; Wang, K.; Weinstein, L. B.; Weller, H.; Weygand, D. P.; Williams, M.; Wolin, E.; Wood, M. H.; Yegneswaran, A.; Yun, J.; Zana, L.; Zhang, J.
2005-11-01
The polarized longitudinal-transverse structure function σLT' measures the interference between real and imaginary amplitudes in pion electroproduction and can be used to probe the coupling between resonant and nonresonant processes. We report new measurements of σLT' in the N(1440)1/2+ (Roper) resonance region at Q2=0.40 and 0.65GeV2 for both the π0p and π+n channels. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at a beam energy of 1.515 GeV. Complete angular distributions were obtained and are compared to recent phenomenological models. The σLT'(π+n) channel shows a large sensitivity to the Roper-resonance multipoles M1- and S1- and provides new constraints on models of resonance formation.
Filin, A A; Epelbaum, E; Hanhart, C; Krebs, H; Myhrer, F
2013-01-01
A calculation of the pion-production operator up to next-to-next-to-leading order for s-wave pions is performed within chiral effective field theory. In the previous study [Phys. Rev. C 85, 054001 (2012)] we discussed the contribution of the pion-nucleon loops at the same order. Here we extend that study to include explicit Delta degrees of freedom and the 1/m_N^2 corrections to the pion-production amplitude. Using the power counting scheme where the Delta-nucleon mass difference is of the order of the characteristic momentum scale in the production process, we calculate all tree-level and loop diagrams involving Delta up to next-to-next-to-leading order. The long-range part of the Delta loop contributions is found to be of similar size to that from the pion-nucleon loops which supports the counting scheme. The net effect of pion-nucleon and Delta loops is expected to play a crucial role in understanding of the neutral pion production data.
Pion polarizabilities: Theory vs Experiment
Ivanov, Mikhail A
2015-01-01
The values of charged pion polarizabilities obtained in the framework of chiral perturbation theory at the level of two-loop accuracy are compared with the experimental result recently reported by COMPASS Collaboration. It is found that the calculated value for the dipole polarizabilities $(\\alpha-\\beta)_{\\pi^\\pm}= (5.7\\pm 1.0)\\times 10^{-4}\\,{\\rm fm}^3$ fits quite well the experimental result $(\\alpha-\\beta)_{\\pi^\\pm} = (4.0 \\pm 1.2_{\\rm stat} \\pm 1.4_{\\rm syst}) \\times 10^{-4}\\,{\\rm fm}^3$.
Covariant formulation of pion-nucleon scattering
Lahiff, A. D.; Afnan, I. R.
A covariant model of elastic pion-nucleon scattering based on the Bethe-Salpeter equation is presented. The kernel consists of s- and u-channel nucleon and delta poles, along with rho and sigma exchange in the t-channel. A good fit is obtained to the s- and p-wave phase shifts up to the two-pion production threshold.
Production of Two Pions Induced by Neutrinos
Valverde, M; Hernández, E; Singh, S K; Vacas, M J Vicente
2008-01-01
We study the threshold production of two pions induced by neutrinos in nucleon targets. The contribution of nucleon pole, pion and contact terms is calculated using a chiral Lagrangian. The contribution of the Roper resonance, neglected in earlier studies, has also been taken into account.
Analysis of Quantum Search Algorithms for Arbitrary Amplitude Distribution%任意幅度分布的量子搜索算法研究
Institute of Scientific and Technical Information of China (English)
吉作约子; 李会方
2011-01-01
针对Grover与Ventura搜索算法并非对任意幅度分布的初态都是有效的问题,结合量子计算的特点,在Ventura算法的基础上提出一种改进算法,并用递归函数的方法分析改进算法幅值的动态范围.最后用Matlab进行了模拟仿真,比较了三种算法的性能.结果表明提出的改进算法能弥补Grover和Ventura算法的不足.如果事先知道m的值,可以选择相应的算法来提高搜索成功的概率.%The problem of Graver' s and Ventura' s algorithms are not effective in any arbitrary amplitude distri-bution are studied. First, combining with the characteristics of quantum computing, a new algorithm is proposed and its amplitude dynamics with recursive function are analyzed. Further, a simulation with Matlab to compare the performance of three algorithms are made. Finally, the conclusion that the proposed algorithm can make up for Grover' s and Ventura' s deficiencies . If the value of m in advance is known, the appropriate algorithm to increase the probability of success can be seected.
Bolokhov, A A; Sherman, S G
1998-01-01
We develop the phenomenological amplitude of the $\\pi N \\to \\pi \\pi N$ reaction describing the exchanges of $\\Delta$ and $N_{*}$ along with the OPE mechanism. The contribution of the latter contains 4 independent low energy parameters (up to $O(k^{4})$ order). The terms of the polynomial background are added to stand for far resonances and for contact terms originating from the off-mass-shell interactions. These terms are introduced with the account of isotopic, crossing, $ C $, $ P $ and $ T $ symmetries of strong interactions. The data consisting of total cross sections in the energy region $ 0.300 \\le P_{Lab} \\le 500 $~MeV/c and 1D distributions from the bubble-chamber experiments for three reaction channels were undergoing fittings to determine free parameters of the amplitude. The best solutions are characterized by $ found to be more important than OPE. The obtained solutions reveal the need in more precise data and/or in polarization measurements because of large correlations of isobar parameters with ...
Analysis of the pion-kaon sigma-term and related topics
Frink, M; Meißner, Ulf G; Frink, Matthias; Kubis, Bastian; Mei{\\ss}ner, Ulf-G.
2002-01-01
We calculate the one-loop contributions to the difference \\Delta_{\\pi K} between the isoscalar on-shell pion-kaon scattering amplitude at the Cheng-Dashen point and the scalar form factor \\Gamma_K (2M_\\pi^2) in the framework of three flavor chiral perturbation theory. These corrections turn out to be small. This is further sharpened by treating the kaons as heavy fields (two flavor chiral perturbation theory). We also analyze the two-loop corrections to the kaon scalar form factor based on a dispersive technique. We find that these corrections are smaller than in the comparable case of the scalar form factor of the pion. This is related to the weaker final state interactions in the pion-kaon channel.
Single pion production in neutrino nucleus scattering
Hernández, E; Vacas, M J Vicente
2013-01-01
We study one pion production in both charged and neutral current neutrino nucleus scattering for neutrino energies below 2 GeV. We use a theoretical model for one pion production at the nucleon level that we correct for medium effects. The results are incorporated into a cascade program that apart from production also includes the pion final state interaction inside the nucleus. Besides, in some specific channels coherent pion production is also possible and we evaluate its contribution as well. Our results for total and differential cross sections are compared with recent data from the MiniBooNE Collaboration. The model provides an overall acceptable description of data, better for NC than for CC channels, although theory is systematically below data. Differential cross sections, folded with the full neutrino flux, show that most of the missing pions lie on the forward direction and at high energies.
Kitaygorsky, J.; Słysz, W.; Shouten, R.; Dorenbos, S.; Reiger, E.; Zwiller, V.; Sobolewski, Roman
2017-01-01
We present a new operation regime of NbN superconducting single-photon detectors (SSPDs) by integrating them with a low-noise cryogenic high-electron-mobility transistor and a high-load resistor. The integrated sensors are designed to get a better understanding of the origin of dark counts triggered by the detector, as our scheme allows us to distinguish the origin of dark pulses from the actual photon pulses in SSPDs. The presented approach is based on a statistical analysis of amplitude distributions of recorded trains of the SSPD photoresponse transients. It also enables to obtain information on energy of the incident photons, as well as demonstrates some photon-number-resolving capability of meander-type SSPDs.
Pion production model - connection between dynamics and quark models
Energy Technology Data Exchange (ETDEWEB)
Lee, T.-S. H.; Sato, T.
2000-05-17
The authors discuss the difficulties in testing the hadron models by using the N{sup *} parameters extracted from the empirical amplitude analyses of the {pi}N and {gamma}N reaction data. As an alternative or perhaps a more advantageous approach, they present a Hamiltonian formulation that can relate the pion production dynamics and the constituent quark models of N{sup *} structure. The application of the approach in investigating the {Delta} and N{sup *}(S{sub 11}) excitations is reviewed. It is found that while the {Delta} excitation can be described satisfactory, the {pi}N scattering in S{sub 11} channel can not be described by the constituent quark models based on either the one-gluon-exchange or one-meson-exchange mechanisms. A phenomenological quark-quark potential has been constructed to reproduce the S{sub 11} amplitude.
Dingus, Peter John
From over 300,000 hadronic events gathered by the BC72/73 collaboration, which directed a 20GeV photon beam onto a liquid hydrogen target, the reaction gamma p to pp ^' was isolated in the channels gamma p to p2pi^+2pi^- and gamma p to ppi^+pi^-2pi^0 . Subsequently various Monte Carlo models of the rho^' decaying into four pions in the charge states 2pi^+2 pi^- and pi^+ pi^-2pi^0 were fit to the data in all pertinent kinematic variables along with the decay angular distributions and various assumed backgrounds that had not been disentangled. The results of this analysis are: (1) The Photoproduced rho^' conserves S channel helicity, this is shown by an analysis of the angle Phi, as described in the text, and by the Density Matrix Elements, (DME), of the rho^' in the channel gamma p to p2pi^+2pi^-. The DMEs, through the Parity Asymmetry, also show the rho^' production to be mostly due to natural parity exchange in the t channel. (2) The dominant decay mode of the rho^' is via rho^' to pi A_1, this is shown by the absence of a rho^0 signal in the channel gamma p to ppi^+pi ^-2pi^0 and by the approximate equality of the rho^' cross sections in the two channels. The rho ^' cross section in the channel gamma p to p2pi^+2pi^- is measured to be 0.944 +/- 0.05 mu b and the rho^' cross section in the channel gamma p to ppi^+ pi^-2pi^0 is measured to be 1.19 +/- 0.089mu b. (3) The rho^' mass and width in the channel gamma p to p2pi^+2 pi^- are determined to be 1.20 +/- 0.05GeV and 0.535 +/- 0.04GeV respectively. In the channel gamma p to ppi^+ pi^-2pi^0 the rho^' mass and width are determined to be 1.25 +/- 0.1GeV and 0.53 +/- 0.06GeV respectively.
Charged pion anisotropy in relativistic nucleus-nucleus collisions
Energy Technology Data Exchange (ETDEWEB)
Poitou, J.; L' Hote, D.; Cavata, C.; Babinet, R.; Demoulins, M.; Fanet, H.; Gosset, J.; Lemaire, M.C.; Le Merdy, A.; Lucas, B.; Terrien, Y.; Valette, O. (CEN Saclay, 91 - Gif-sur-Yvette (France)); Alard, J.P.; Augerat, J.; Bastid, N.; Charmensat, P.; Dupieux, P.; Fraysse, L.; Marroncle, J.; Montarou, G.; Parizet, M.J.; Rahmani, A. (LPC Clermont-Ferrand, 63 - Aubiere (France)); Brochard, F.; Gorodetzky, P.; Racca, C. (CRN, 67 - Strasbourg (France))
1992-01-27
The momentum distributions with respect to the reaction plane for charged pions emitted in Ne-nucleus and Ar-nucleus collisions have been measured with the 4{pi} detector Diogene at the Saturne synchrotron. The reaction plane is estimated from the baryon momenta, using a standard technique for flow analysis. The pions exhibit a non-zero flow. For asymmetric systems, there is a preferential emission in the direction of the lighter (projectile) nucleus. Such a behaviour contradicts the predictions of INC calculations and is underestimated by QMD calculations which include mean field effects. It can be interpreted with a simple geometrical model in terms of absorption by the spectator nuclear matter. (orig.).
Neutrino Induced Coherent Pion Production off Nuclei and PCAC
Hernández, E; Vicente-Vacas, M J
2009-01-01
We have critically reviewed the commonly used Rein--Sehgal model for neutrino induced coherent pion production. We have studied the validity of the main approximations implicit in that model, trying to compare with physical observables when that is possible and with microscopical calculations. Next, we have tried to elaborate a new improved model by removing the more problematic approximations, while keeping the model still reasonably simple. Last, we have discussed the limitations intrinsic to any approach based on the partial conservation of the axial current hypothesis. In particular, we have shown the inability of such models to determine the angular distribution of the outgoing pion with respect to the direction of the incoming neutrino, except for the $q^2= 0$ kinematical point.
Fu, Hai-Bing; Han, Hua-Yong; Ma, Yang
2014-01-01
The QCD light-cone sum rules (LCSR) provides an effective way for dealing with the heavy-to-light transition form factors (TFFs), whose non-perturbative dynamics are parameterized into the light-meson's light-cone distribution amplitudes (LCDAs) with various twist structures. By taking the chiral correlator as the starting point, we calculate the LCSRs for the $B\\to\\rho$ TFFs up to twist-4 accuracy. As for the TFFs at the large recoil region, we observe that the twist-2 transverse DA $\\phi_{2;\\rho}^\\bot$ provides the dominant contribution, while the contributions from the remaining twist-3 and twist-4 terms are $\\delta^2$-suppressed. Thus, our present improved LCSRs provides a good platform for testing the $\\phi_{2;\\rho}^\\bot$ behavior. For the purpose, we suggest a convenient WH-model for the $\\rho$-meson leading-twist wavefunction, in which the parameter $B_{2;\\rho}^\\bot\\sim a^\\bot_2$ dominantly controls its longitudinal distribution. Typically, its DA $\\phi_{2;\\rho}^\\bot$ is CZ-like as $B_{2;\\rho}^\\bot\\sim...
Chiral Dynamics in Pion-Photon Reactions Habilitation
Friedrich, Jan Michael
As the lightest particle of the strong force, the pion plays a central role in the field of strong interactions, and understanding its properties is of prime relevance for understanding the strong interaction in general. The low-energy behaviour of pions is of particular interest. Although the quark-gluon substructure and their quantum chromodynamics is not apparent then, this specific inner structure causes the presence of approximate symmetries in pion-pion interactions and in pion decays, which gives rise to the systematic description of processes involving pions in terms of few low-energy constants. Specifically, the chiral symmetry and its spontaneous and explicit breaking, treated in chiral perturbation theory (ChPT), leads to firm predictions for low-energy properties of the pion. To those belong the electromagnetic polarisabilities of the pion, describing the leading-order structure effect in pion Compton scattering. The research presented in this work is concerned with the interaction of pions and ph...
Parton-to-Pion Fragmentation Reloaded
de Florian, D; Epele, M; Hernandez-Pinto, R J; Stratmann, M
2014-01-01
We present a new, comprehensive global analysis of parton-to-pion fragmentation functions at next-to-leading order accuracy in QCD. The obtained results are based on the latest experimental information on single-inclusive pion production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An excellent description of all data sets is achieved, and the remaining uncertainties in parton-to-pion fragmentation functions are estimated based on the Hessian method. Extensive comparisons to the results from our previous global analysis are performed.
Symmetry limit properties of decay amplitudes with mirror matter admixtures
Sánchez-Colón, G; Sanchez-Colon, Gabriel; Garcia, Augusto
2006-01-01
We extend our previous analysis on the symmetry limit properties of non-leptonic and weak radiative decay amplitudes of hyperons in a scheme of mirror matter admixtures in physical hadrons to include the two-body non-leptonic decays of $\\Omega^-$ and the two photon and two pion decays of kaons. We show that the so-called parity-conserving amplitudes predicted for all the decays vanish in the strong flavor SU(3) symmetry limit. We also establish the specific conditions under which the corresponding so-called parity-violating amplitudes vanish in the same limit.
Fantazzini, Paola; Galassi, Francesca; Bortolotti, Villiam; Brown, Robert J. S.; Vittur, Franco
2011-06-01
When inverting nuclear magnetic resonance relaxation data in order to obtain quasi-continuous distributions of relaxation times for fluids in porous media, it is common practice to impose a non-negative (NN) constraint on the distributions. While this approach can be useful in reducing the effects of data distortion and/or preventing wild oscillations in the distributions, it may give misleading results in the presence of real negative amplitude components. Here, some examples of valid negative components for articular cartilage and hydrated collagen are given. Articular cartilage is a connective tissue, consisting mainly of collagen, proteoglycans and water, which can be considered, in many aspects, as a porous medium. Separate T1 relaxation data are obtained for low-mobility ('solid') macromolecular 1H and for higher-mobility ('liquid') 1H by the separation of these components in free induction decays, with α denoting the solid/liquid 1H ratio. When quasi-continuous distributions of relaxation times (T1) of the solid and liquid signal components of cartilage or collagen are computed from experimental relaxation data without imposing the usual NN constraint, valid negative peaks may appear. The features of the distributions, in particular negative peaks, and the fact that peaks at longer times for macromolecular and water protons are at essentially the same T1, are interpreted as the result of a magnetization exchange between these two spin pools. For the only-slightly-hydrated collagen samples, with α>1, the exchange leads to small negative peaks at short T1 times for the macromolecular component. However, for the cartilage, with substantial hydration or for a strongly hydrated collagen sample, both with αLt1, the behavior is reversed, with a negative peak for water at short times. The validity of a negative peak may be accepted (dismissed) by a high (low) cost of NN in error of fit. Computed distributions for simulated data using observed signal
Scaling study of the pion electroproduction cross sections and the pion form factor
Energy Technology Data Exchange (ETDEWEB)
Tanja Horn; Xin Qian; John Arrington; Razmik Asaturyan; Fatiha Benmokthar; Werner Boeglin; Peter Bosted; Antje Bruell; Eric Christy; Eugene Chudakov; Ben Clasie; Mark Dalton; AJI Daniel; Donal Day; Dipangkar Dutta; Lamiaa El Fassi; Rolf Ent; Howard Fenker; J. Ferrer; Nadia Fomin; H. Gao; K Garrow; Dave Gaskell; C Gray; G. Huber; M. Jones; N Kalantarians; C. Keppel; K Kramer; Y Li; Y Liang; A. Lung; S Malace; P. Markowitz; A. Matsumura; D. Meekins; T Mertens; T Miyoshi; H. Mykrtchyan; R. Monson; T. Navasardyan; G. Niculescu; I. Niculescu; Y. Okayasu; A. Opper; C Perdrisat; V. Punjabi; A. Rauf; V. Rodriguez; D. Rohe; J Seely; E Segbefia; G. Smith; M. Sumihama; V. Tadevoyan; L Tang; V. Tvaskis; A. Villano; W. Vulcan; F. Wesselmann; S. Wood; L. Yuan; X. Zheng
2007-07-12
The $^{1}$H($e,e^\\prime \\pi^+$)n cross section was measured for a range of four-momentum transfer up to $Q^2$=3.91 GeV$^2$ at values of the invariant mass, $W$, above the resonance region. The $Q^2$-dependence of the longitudinal component is consistent with the $Q^2$-scaling prediction for hard exclusive processes. This suggests that perturbative QCD concepts are applicable at rather low values of $Q^2$. Pion form factor results, while consistent with the $Q^2$-scaling prediction, are inconsistent in magnitude with perturbative QCD calculations. The extraction of Generalized Parton Distributions from hard exclusive processes assumes the dominance of the longitudinal term. However, transverse contributions to the cross section are still significant at $Q^2$=3.91 GeV$^2$.
Pion decay within the framework of Very Special Relativity
Nayak, Alekha C
2016-01-01
We illustrate some new and novel effects which arise in decay and scattering experiments within the framework of Very Special Relativity (VSR) using the charged pion decay process as an example. It is assumed that there is a small violation of Lorentz invariance and the true symmetry group of nature is a subgroup called SIM(2). This symmetry group postulates the existence of a fundamental or preferred direction in space-time. We construct effective interaction terms which violate Lorentz invariance but respect SIM(2) and impose a limit on the corresponding coupling strength using the observed pion decay rate. We also predict a shift in the angular dependence of the decay products due to VSR. In particular we find that these no longer display azimuthal symmetry with respect to the momentum of the pion. Furthermore the azimuthal and polar angle distributions show time dependence with a period of a sidereal day. This time dependence provides us with a novel method to test VSR in future experiments.
Precise analysis of pion-pion scattering data from Roy equations and forward dispersion relations
Peláez, J R; Kaminski, R; Ynduráin, F J
2008-01-01
We review our recent analysis of pion-pion scattering data in terms of Roy equations and Forward Dispersion Relations, and present some preliminary results in terms of a new set of once-subtracted coupled equations for partial waves. The first analysis consists of independent fits to the different pion-pion channels that satisfies rather well the dispersive representation. In the second analysis we constrain the fit with the dispersion relations. The latter provides a very precise and model independent description of data using just analyticity, causality and crossing.
Chiral pions in a magnetic background
Energy Technology Data Exchange (ETDEWEB)
Colucci, G., E-mail: colucci@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany); Fraga, E.S., E-mail: fraga@if.ufrj.br [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, D-60438 Frankfurt am Main (Germany); Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21945-970 (Brazil); Sedrakian, A., E-mail: sedrakian@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany)
2014-01-20
We investigate the modification of the pion self-energy at finite temperature due to its interaction with a low-density, isospin-symmetric nuclear medium embedded in a constant magnetic background. To one loop, for fixed temperature and density, we find that the pion effective mass increases with the magnetic field. For the π{sup −}, interestingly, this happens solely due to the trivial Landau quantization shift ∼|eB|, since the real part of the self-energy is negative in this case. In a scenario in which other charged particle species are present and undergo an analogous trivial shift, the relevant behavior of the effective mass might be determined essentially by the real part of the self-energy. In this case, we find that the pion mass decreases by ∼10% for a magnetic field |eB|∼m{sub π}{sup 2}, which favors pion condensation at high density and low temperatures.
Chiral pions in a magnetic background
Colucci, Giuseppe; Sedrakian, Armen
2013-01-01
We investigate the modification of the pion self-energy at finite temperature due to its interaction with a low-density, isospin-symmetric nuclear medium embedded in a constant magnetic background. To one loop, for fixed temperature and density, we find that the pion effective mass increases with the magnetic field. For the $\\pi^{-}$, interestingly, this happens solely due to the trivial Landau quantization shift $\\sim |eB|$, since the real part of the self-energy is negative in this case. In a scenario in which other charged particle species are present and undergo an analogous trivial shift, the relevant behavior of the effective mass might be determined essentially by the real part of the self-energy. In this case, we find that the pion mass decreases by $\\sim 10%$ for a magnetic field $|eB|\\sim m_\\pi^2$, which favors pion condensation at high density and low temperatures.
Chiral pions in a magnetic background
Colucci, G.; Fraga, E. S.; Sedrakian, A.
2014-01-01
We investigate the modification of the pion self-energy at finite temperature due to its interaction with a low-density, isospin-symmetric nuclear medium embedded in a constant magnetic background. To one loop, for fixed temperature and density, we find that the pion effective mass increases with the magnetic field. For the π-, interestingly, this happens solely due to the trivial Landau quantization shift ∼|eB|, since the real part of the self-energy is negative in this case. In a scenario in which other charged particle species are present and undergo an analogous trivial shift, the relevant behavior of the effective mass might be determined essentially by the real part of the self-energy. In this case, we find that the pion mass decreases by ∼10% for a magnetic field |eB|∼mπ2, which favors pion condensation at high density and low temperatures.
Anomalous electromagnetism of pions and magnons
Energy Technology Data Exchange (ETDEWEB)
Wiese, U.-J. [Institute for Theoretical Physics, Bern University Sidlerstrasse 5, CH-3012 Bern (Switzerland)
2005-04-15
Pions and magnons - the Goldstone bosons of the strong interactions and of magnetism - share a number of common features. Pion and magnon fields couple anomalously to electromagnetism through the conserved Goldstone-Wilczek current of their topological Skyrmion excitations. In the pion case, this coupling gives rise to the decay of the neutral pion into two photons. In the magnon case, the anomalous coupling leads to photonmagnon conversion in an external magnetic field. A measurement of the conversion rate in quantum Hall ferromagnets determines the anyon statistics angle of baby-Skyrmions. If photon-magnon conversion also occurs in antiferromagnets, baby-Skyrmions carry electric charge and may represent the Cooper-pairs of high-temperature superconductors.
Pion production in nucleon-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Afnan, I.R.
1982-01-01
A model describing pion production in proton-proton interactions is presented. The model includes both single nucleon and two nucleon mechanisms. A system of equations representing the reaction is derived and results calculated using these equations are presented.
Surovtsev, Yu S; Gutsche, T; Kamiński, R; Lyubovitskij, V E; Nagy, M
2016-01-01
It is shown that the basic shape of dipion mass distributions in the two-pion transitions of both charmonia and bottomonia states are explained by an unified mechanism based on the contribution of the $\\pi\\pi$, $K\\overline{K}$ and $\\eta\\eta$ coupled channels including their interference.
Hunting the QCD-Odderon in hard diffractive electroproduction of two pions
Hägler, P; Szymanowski, L; Teryaev, O V; H\\"agler, Ph.
2002-01-01
Charge asymmetries in diffractive electroproduction of two mesons are proportional to the interference of Pomeron and Odderon exchange amplitudes. We calculate in the framework of QCD and in the Born approximation a forward-backward charge asymmetry which turns out to be sizable in a kinematical domain accessible to HERA experiments. We predict a distinctive dependence of this asymmetry on the invariant mass of the two pions. Testing this prediction is a crucial step in the discovery of the QCD-Odderon.
Threshold pion production in proton-proton collisions at NNLO in chiral EFT
Energy Technology Data Exchange (ETDEWEB)
Baru, V. [Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik II, Bochum (Germany); Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Epelbaum, E.; Filin, A.A.; Krebs, H. [Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik II, Bochum (Germany); Hanhart, C. [Forschungszentrum Juelich, Institut fuer Kernphysik, (Theorie) and Juelich Center for Hadron Physics, Juelich (Germany); Forschungszentrum Juelich, Institute for Advanced Simulation, Juelich (Germany); Myhrer, F. [University of South Carolina, Department of Physics and Astronomy, Columbia, SC (United States)
2016-05-15
The reaction NN→NNπ offers a good testing ground for chiral effective field theory at intermediate energies. It challenges our understanding of the first inelastic channel in nucleon-nucleon scattering and of the charge symmetry breaking pattern in hadronic reactions. In our previous studies, we presented a complete calculation of the pion production operator for s-wave pions up-to-and-including next-to-next-to-leading order (NNLO) in the formulation of chiral effective field theory, which includes pions, nucleons and Δ(1232) degrees of freedom. In this paper we calculate the near-threshold cross section for the pp → dπ{sup +} reaction by performing the convolution of the obtained operators with nuclear wave functions based on modern phenomenological and chiral potentials. The available chiral NN wave functions are constructed with a cutoff comparable with the momentum transfer scale inherent in pion production reactions. Hence, a significant portion of the dynamical intermediate-range physics is thereby cut off by them. On the other hand, the NNLO amplitudes evaluated with phenomenological wave functions appear to be largely independent of the NN model used and give corrections to the dominant leading-order contributions as expected from dimensional analysis. The result gives support to the counting scheme used to classify the pion production operators, which is a precondition for a reliable investigation of the chirally suppressed neutral pion production. The explicit inclusion of the Δ(1232) is found to be important but smaller than expected due to cancellations. (orig.)
Pion Polarizabilities from $\\gamma\\gamma\\to\\pi\\pi$ Analysis
Dai, Ling-Yun
2016-01-01
We present results for pion polarizabilities predicted using dispersion relations from our earlier Amplitude Analysis of world data on two photon production of meson pairs. The helicity-zero polarizabilities are rather stable and insensitive to uncertainties in cross-channel exchanges. The need is first to confirm the recent result on $(\\alpha_1-\\beta_1)$ for the charged pion by COMPASS at CERN to an accuracy of 10\\% by measuring the $\\gamma\\gamma\\to\\pi^+\\pi^-$ cross-section to an uncertainty of ~1\\%. Then the same polarizability, but for the $\\pi^0$, is fixed to be $(\\alpha_1-\\beta_1)_{\\pi^0}=(0.9\\pm0.2)\\times 10^{-4}$ fm$^{3}$. By analyzing the correlation between uncertainties in the meson polarizability and those in $\\gamma\\gamma$ cross-sections, we suggest experiments need to measure these cross-sections between $\\sqrt{s}\\simeq 350$ and 600~MeV. The $\\pi^0\\pi^0$ cross-section then makes the $(\\alpha_2-\\beta_2)_{\\pi^0}$ the easiest helicity-two polarizability to determine.
Neutral pion photoproduction of the nucleon near threshold
Energy Technology Data Exchange (ETDEWEB)
Nozawa, S.; Lee, T.S.H.; Blankleider, B. (Argonne National Lab., IL (USA); Patterson, Moos and Co., Inc., Long Island City, NY (USA))
1989-01-01
Neutral pion photoproduction on the nucleon near threshold is investigated using a dynamical model. It is shown that the commonly used procedure, based on an analytical continuation of the K-matrix to the unphysical region, is not compatible to a dynamical approach. We show that the final state interaction (FSI) amplitude derived from a dynamical model could involve large cancellation between the different pion photoproduction mechanisms. This leads that the FSI due to the intermediate {pi}{sup 0}p state can be as important as that due to the {pi}{sup +}n intermediate state. At threshold, we obtain E{sub 0+} = {minus}1.92 {times} 10{sup {minus}3}/m{sub {pi}+}. This number is close to the measured value of E{sub 0+} = {minus}1.5 {times} 10{sup {minus}3}/m{sub {pi}+}. No violation of the low energy theorem is required to obtain good agreement between the calculated total cross sections and experimental data drum threshold to about 400 MeV incident photon energy. 10 refs., 4 figs., 3 tabs.
Pion production: A probe for coherence in medium-energy heavy-ion collisions
Energy Technology Data Exchange (ETDEWEB)
Stachel, J.; Braun-Munzinger, P.; Freifelder, R.H.; Paul, P.; Sen, S.; DeYoung, P.; Zhang, P.H.; Awes, T.C.; Obenshain, F.E.; Plasil, F.
1986-04-01
The production of neutral pions has been studied in reactions of 35 MeV/nucleon /sup 14/N+ /sup 27/Al,Ni,W and 25 MeV/nucleon /sup 16/O+ /sup 27/Al,Ni. Inclusive pion differential distributions dsigma/dT/sub ..pi../, dsigma/d..cap omega.., dsigma/dy, dsigma/dp/sub perpendicular/, and d/sup 2/sigma/dy dp/sub perpendicular/ have been measured by detecting the two pion-decay ..gamma.. rays in a setup of 20 lead glass Cerenkov detector telescopes. Special care was taken to understand and suppress background events. Effects of pion reabsorption are discussed and it is found that the cross sections presented here are substantially affected by such final state interactions. The comparatively large experimental cross sections and the shape of the spectral distributions cannot be accounted for in single nucleon-nucleon collision or statistical models; they rather call for a coherent pion production mechanism.
Proton and pion production in Au+Au collisions at 10.8A GeV/c
Energy Technology Data Exchange (ETDEWEB)
Barrette, J. [McGill University, Montreal, Canada H3A 2T8 (Canada); Bellwied, R. [Wayne State University, Detroit, Michigan 48202 (United States); Bennett, S. [Wayne State University, Detroit, Michigan 48202 (United States); Bersch, R. [SUNY at Stony Brook, Stony Brook, New York 11794 (United States); Braun-Munzinger, P. [Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt, (Germany); Chang, W. C. [SUNY at Stony Brook, Stony Brook, New York 11794 (United States); Cleland, W. E. [University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Clemen, M. [University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Cole, J. [Idaho National Engineering Laboratory, Idaho Falls, Idaho 83402 (United States); Cormier, T. M. [Wayne State University, Detroit, Michigan 48202 (United States)] (and others)
2000-08-01
We present proton and pion tranverse momentum spectra and rapidity distributions for Au+Au collisions at 10.8A GeV/c. The proton spectra exhibit collective transverse flow effects. Evidence of the influence of the Coulomb interaction from the fireball is found in the pion transverse momentum spectra. The data are compared with the predictions of the RQMD event generator. (c) 2000 The American Physical Society.
Energy Technology Data Exchange (ETDEWEB)
Molitoris, J.; Bonasera, A.; Adorno, A.
1993-04-01
The authors study pion production at subthreshold energies in nucleus-collisions using the extended Boltzmann-Nordheim-Vlasov (BNV) model. The extreme sensitivity of the pion yield to the initial momentum space Fermi distribution is demonstrated. The effect of the three body collision term is also shown to be substantial. However, the nuclear equation of state has no significant effect at these energies. Details and implications of the nuclear kinetic equation simulation are discussed.
Elastic and inelastic pion reactions on few nucleon systems
Energy Technology Data Exchange (ETDEWEB)
Lensky, V.
2007-09-29
In the present work, we are studying elastic and inelastic pion reactions on few-body systems within the framework of chiral effective theory. We consider two specific reactions involving pions on few-nucleon systems, namely pion production in nucleon-nucleon collisions, and incoherent pion photoproduction on the deuteron. These two reactions are closely related to the issue of dispersive and absorptive corrections to the pion-deuteron scattering length, which we also consider in our analysis. The incoherent pion photoproduction is also considered as the possible source for a high-precision determination of the neutron-neutron scattering length. (orig.)
Isospin breaking in pion-deuteron scattering and the pion-nucleon scattering lengths
Hoferichter, Martin; Hanhart, Christoph; Kubis, Bastian; Nogga, Andreas; Phillips, Daniel R
2012-01-01
In recent years, high-accuracy data for pionic hydrogen and deuterium have become the primary source of information on the pion-nucleon scattering lengths. Matching the experimental precision requires, in particular, the study of isospin-breaking corrections both in pion-nucleon and pion-deuteron scattering. We review the mechanisms that lead to the cancellation of potentially enhanced virtual-photon corrections in the pion-deuteron system, and discuss the subtleties regarding the definition of the pion-nucleon scattering lengths in the presence of electromagnetic interactions by comparing to nucleon-nucleon scattering. Based on the pi^{+/-} p channels we find for the virtual-photon-subtracted scattering lengths in the isospin basis a^{1/2}=(170.5 +/- 2.0) x 10^{-3} mpi^{-1} and a^{3/2}=(-86.5 +/- 1.8) x 10^{-3} mpi^{-1}.
Energy Technology Data Exchange (ETDEWEB)
Fantazzini, Paola; Galassi, Francesca [Department of Physics, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna (Italy); Bortolotti, Villiam [Department of DICAM, University of Bologna, Viale del Risorgimento 2, 40136 Bologna (Italy); Brown, Robert J S [953 West Bonita Avenue, Claremont, CA 91711-4193 (United States); Vittur, Franco, E-mail: paola.fantazzini@unibo.it [Department of Life Sciences, University of Trieste, via Giorgeri 1, 24137 (Italy)
2011-06-15
When inverting nuclear magnetic resonance relaxation data in order to obtain quasi-continuous distributions of relaxation times for fluids in porous media, it is common practice to impose a non-negative (NN) constraint on the distributions. While this approach can be useful in reducing the effects of data distortion and/or preventing wild oscillations in the distributions, it may give misleading results in the presence of real negative amplitude components. Here, some examples of valid negative components for articular cartilage and hydrated collagen are given. Articular cartilage is a connective tissue, consisting mainly of collagen, proteoglycans and water, which can be considered, in many aspects, as a porous medium. Separate T{sub 1} relaxation data are obtained for low-mobility ('solid') macromolecular {sup 1}H and for higher-mobility ('liquid') {sup 1}H by the separation of these components in free induction decays, with {alpha} denoting the solid/liquid {sup 1}H ratio. When quasi-continuous distributions of relaxation times (T{sub 1}) of the solid and liquid signal components of cartilage or collagen are computed from experimental relaxation data without imposing the usual NN constraint, valid negative peaks may appear. The features of the distributions, in particular negative peaks, and the fact that peaks at longer times for macromolecular and water protons are at essentially the same T{sub 1}, are interpreted as the result of a magnetization exchange between these two spin pools. For the only-slightly-hydrated collagen samples, with {alpha}>1, the exchange leads to small negative peaks at short T{sub 1} times for the macromolecular component. However, for the cartilage, with substantial hydration or for a strongly hydrated collagen sample, both with {alpha}<<1, the behavior is reversed, with a negative peak for water at short times. The validity of a negative peak may be accepted (dismissed) by a high (low) cost of NN in error of fit
球形夸克-胶子等离子体演化源的π干涉学分析%Pion Interferometry for Spherical Quark-Gluon Plasma Evolution Sources
Institute of Scientific and Technical Information of China (English)
Efaaf M.J.; 张卫宁; Khaliliasr M.; 金恩培; 刘亦铭
2005-01-01
We examine the two-pion interferometry for the expanding sources of spherical quark-gluon plasma evolution. The quarkgluon plasma evolution is described by relativistic hydrodynamics with the equation of state of entropy density. The two-pion HanburyBrown-Twiss (HBT) correlation functions are calculated using quantum probability amplitudes in a path-integral formalism. We find the spatial parameter extracted by the two-pion interferometry is sensitive to the phase-space distribution of the pion-emitting source.The expanding velocity of the source leads to a smaller HBT radius and changes the relationship between the HBT radius and the freeze-ont temperature.%本文对球形演化的夸克-胶子等离子体膨胀源进行了2π干涉学分析.夸克-胶子等离子体的演化由相对论流体力学和熵密度的物态方程描述,而2πHanbury-Brown-Twiss(HBT)关联函数由量子几率振幅的路径积分公式计算.研究结果表明,由2π干涉学得到的源的空间参量敏感地依赖于π介子发射源的相空间分布,源的膨胀速度导致HBT半径变小,并会改变HBT半径与冻结温度之间的关系.
Single-spin asymmetries in semi-inclusive pion production
Elschenbroich, U
2005-01-01
For the first time single-spin asymmetries in semi-inclusive pion production are measured by the HERMES experiment with a transversely polarised hydrogen target. Two different sine-modulations are extracted which can be related to the transversity \\delta q(x) and Sivers f_{1T}^{\\perp q}(x) quark distribution functions. The extracted sine-moments still contain small sub-leading twist contributions which can be extracted from HERMES data combining the results from the transversely polarised hydrogen target with previously measured results from a longitudinally polarised hydrogen target.
Measurement Of Double-radiative Pion Capture On Hydrogen
Tripathi, S
2003-01-01
The first measurement of double radiative pion capture on hydrogen is presented. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer, and detected γ-ray coincidences following π − stops in liquid hydrogen. The branching ratio for the double radiative capture reaction was found to be (3.05 ± 0.27 (stat.) ± 0.31 (syst.)) × 10−5. The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the π−π + → γγ annihilation mechanism.
Electron and pion scattering off nuclei
Energy Technology Data Exchange (ETDEWEB)
Buss, O.; Mosel, U. [Inst. fuer Theoretische Physik, Univ. Giessen (Germany); Alvarez-Ruso, L. [Dept. de Fisica Teorica and IFIC, Centro Mixto Univ. de Valencia-CSIC (Spain)
2007-07-01
We present a treatment of pion and electron scattering off nuclei within the framework of a Boltzmann-Uehling-Uhlenbeck (BUU) transport model. In this approach we realize a full coupled channel treatment and include medium modifications such as mean-field potentials, Fermi motion and width modifications. We have applied the GiBUU model to the description of the double charge exchange (DCX) reaction of pions with different nuclear targets at incident kinetic energies of 120-180 MeV. The DCX process is highly sensitive to details of the interactions of pions with the nuclear medium and, therefore, represents a major benchmark for any model of pion scattering off nuclei at low and intermediate energies. We discuss the impact of surface effects and the dependence on the nuclear mass number. We have achieved a good quantitative agreement with the extensive data set obtained at LAMPF. Furthermore, we present a description of electron induced reactions, i.e. pion production, off nuclei. We consider the scattering of electrons off the bound nucleons in an impulse approximation and investigate medium modifications to exclusive particle production cross sections and compare our results to available data. (orig.)
K to \\pi\\pi decays and the K to \\sigma weak amplitude
Trofimenkoff, N N
2012-01-01
We use a twice-subtracted partial-wave dispersion relation in the elastic unitarity approximation for final-state interactions to study the amplitude for the delta I = 1/2 CP-conserving weak process K+spurion->pi+pi. We use a simple parameterization to approximate the low energy I = 0 S-wave pipi->pipi scattering phase shift and extract the residue of the sigma pole in the weak amplitude obtained from the dispersion relation. Using this residue, we relate the K->pipi decay amplitude, the weak amplitude at the soft pion point and the K->sigma weak amplitude.
Low emittance pion beams generation from bright photons and relativistic protons
Serafini, L; Petrillo, V
2015-01-01
Present availability of high brilliance photon beams as those produced by X-ray Free Electron Lasers in combination with intense TeV proton beams typical of the Large Hadron Collider makes it possible to conceive the generation of pion beams via photo-production in a highly relativistic Lorentz boosted frame: the main advantage is the low emittance attainable and a TeV-class energy for the generated pions, that may be an interesting option for the production of low emittance muon and neutrino beams. We will describe the kinematics of the two classes of dominant events, i.e. the pion photo-production and the electron/positron pair production, neglecting other small cross-section possible events like Compton and muon pair production. Based on the phase space distributions of the pion and muon beams we will analyze the pion beam brightness achievable in three examples, based on advanced high efficiency high repetition rate FELs coupled to LHC or Future Circular Collider (FCC) proton beams, together with the stud...
Pion and kaon structure functions at 12 GeV JLab and EIC
Horn, Tanja
2017-01-01
Pions and kaons are, along with protons and neutrons, the main building blocks of nuclear matter. They are connected to the Goldstone modes of dynamical chiral symmetry breaking, the mechanism thought to generate all hadron mass in the visible universe. The distribution of the fundamental constituents, the quarks and gluons, is expected to be different in pions, kaons, and nucleons. However, experimental data are sparse. As a result, there has been persistent doubt about the behavior of the pion's valence quark structure function at large Bjorken-x and virtually nothing is known about the contribution of gluons. A 12 GeV JLab experiment using tagged DIS may contribute to the resolution of the former. The Electron-Ion Collider with an acceptance optimized for forward physics could provide access to structure functions over a larger kinematic region. This would allow for measurements testing if the origin of mass is encoded in the differences of gluons in pions, kaons, and nucleons, and measurements testing assumptions used in the extraction of structure functions and the pion and kaon form factors. Electroweak measurements at an EIC would also potentially allow to disentangle the role of quark flavors at high x. In this talk we will discuss the prospects of such measurements. Supported in part by NSF grants PHY-1306227 and PHY-1306418.
Directory of Open Access Journals (Sweden)
Barnaföldi G.G.
2011-04-01
Full Text Available Resonance production and decay into pion pairs is simulated in a non-extensive quark matter with multi-particle interactions. Final state pion spectra are found to take the form of the Tsallis distribution, in accordance with measurements. It has also been shown that, if a large number of particles with these multi-particle interactions are constrained to a constant energy hyper-surface in phase space, the one-particle distribution is the Tsallis distribution.
Search for a neutral particle of mass 33.9 MeV in pion decay
Energy Technology Data Exchange (ETDEWEB)
Daum, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)
1996-11-01
We have measured the muon momentum distribution in charged pion decay in flight in order to search for a small branching fraction {eta} of pion decays {pi}{sup +}{yields}{mu}{sup +} 1 X, in which a heavy neutral particle X with a mass of 33.9 MeV would be emitted. Such a particle was postulated by the KARMEN collaboration as a possible explanation for an anomaly in their time-of-flight spectrum. In a first experiment we found an upper limit of {eta}{<=}2.6.10{sup -8} at a confidence level of 95%. (author) 4 figs., 9 refs.
Charged Pion Production in 2 to 8 AGeV Central Au+Au Collisions
Klay, J L; Alexander, J M; Anderson, M G; Best, D; Brady, F P; Case, T; Caskey, W; Cebra, D; Chance, J L; Chung, P; Cole, B; Crowe, K; Das, A C; Draper, J E; Gilkes, M L; Gushue, S; Heffner, M; Hirsch, A S; Hjort, E L; Huo, L; Justice, M; Kaplan, M; Keane, D; Kintner, J C; Krofcheck, D; Lacey, R A; Lauret, J; Law, C; Lisa, M A; Liu, H; Liu, Y M; McGrath, R; Milosevich, Z; Odyniec, Grazyna Janina; Olson, D L; Panitkin, S Y; Pinkenburg, C H; Porile, N T; Rai, G; Ritter, H G; Romero, J L; Scharenberg, R P; Srivastava, B; Stone, N T B; Symons, T J M; Wang, S; Wells, R; Whitfield, J; Wienold, T; Witt, R; Wood, L; Zhang Wei Ning
2003-01-01
Momentum spectra of charged pions over nearly full rapidity coverage from target to beam rapidity have been measured in the 0-5% most central Au+Au collisions in the beam energy range from 2 to 8 AGeV by the E895 Experiment. Using a thermal parameterization to fit the transverse mass spectra, rapidity density distributions are extracted. The observed spectra are compared with predictions from the RQMD v2.3 cascade model and also to a thermal model including longitudinal flow. The total 4$pi$ yields of the charged pions are used to infer an initial state entropy produced in the collisions.
Measurement of Collins asymmetry in inclusive production of pion pairs at BaBar
Directory of Open Access Journals (Sweden)
Garzia Isabella
2015-01-01
Full Text Available We present a measurement of the azimuthal asymmetries induced by the Collins effect in inclusive production of pion pairs in the e+e− → ππX annihilation process, where two charged pion pairs are produced in opposite hemispheres. The data collected by the BABAR detector at the SLAC Linear Accelerator Laboratory allows the determination of the Collins fragmentation function as a function of the pion fractional energies and transverse momenta, as well as the determination of its behavior in a 4-dimensional space. These results can be combined with semi-inclusive deep inelastic scattering data to extract the transversity parton distribution function, which is the least known leading-twist component of the QCD description of the nucleon.
Systematics of pion emission in heavy ion collisions in the 1A GeV regime
Reisdorf, W; Barret, V; Basrak, Z; Bastid, N; Benabderrahmane, M L; Caplar, R; Crochet, P; Dupieux, P; Dzelalija, M; Fodor, Z; Grishkin, Y; Hartmann, O N; Herrmann, N; Hildenbrand, K D; Hong, B; Kang, T I; Kecskeméti, J; Kim, Y J; Kirejczyk, M; Kis, M; Koczón, P; Korolija, M; Kotte, R; Kress, T; Lebedev, A; Leifels, Y; López, X; Matulewicz, T; Merschmeyer, M; Neubert, W; Petrovici, M; Rami, F; Ryu, M S; Schüttauf, A; Seres, Z; Sikora, B; Sim, K S; Simion, V; Siwek-Wilczynska, K; Smolyankin, V; Stockmeier, M R; Stoicea, G; Tyminski, Z; Wisniewski, K; Wohlfarth, D; Xiao, Z G; Xu, H S; Yushmanov, I; Zhilin, A; al, et
2006-01-01
Using the large acceptance apparatus FOPI, we study pion emission in the reactions (energies in GeV/nucleon are given in parentheses): 40Ca+40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 96Ru+96Ru (0.4, 1.0, 1.5), 96Zr+96Zr (0.4, 1.0, 1.5), 197Au+197Au (0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include longitudinal and transverse rapidity distributions and stopping, polar anisotropies, pion multiplicities, transverse momentum spectra, ratios for positively and negatively charged pions of average transverse momenta and of yields, directed flow, elliptic flow. The data are compared to earlier data where possible and to transport model simulations.
AZIMUTHAL ASYMMETRY OF NEUTRAL PION EMISSION IN AU+AU REACTIONS AT 1-GEV NUCLEON
VENEMA, LB; BRAAK, H; LOHNER, H; RASCHKE, AE; SIEMSSEN, RH; SUMBERA, M; WILSCHUT, HW; BERG, FD; KUHN, W; METAG, [No Value; NOTHEISEN, M; NOVOTNY, R; PFEIFFER, M; RITMAN, J; SCHWALB, O; GOBBI, A; HILDENBRAND, KD; HLAVAC, S; HOLZMANN, R; SIMON, RS; SODAN, U; TEH, K; WESSELS, JP; HERRMANN, N; WIENOLD, T; KOTTE, R; MOSNER, J; NEUBERT, W; WOHLFARTH, D; OSTENDORF, R; SCHUTZ, Y; BRUMMUND, N; SANTO, R
1993-01-01
The azimuthal angle distributions of neutral pions at midrapidity from Au+Au reactions at 1 GeV/nucleon incident energy have been measured. An enhanced emission of pi0's perpendicular to the reaction plane is observed. The azimuthal asymmetry is dependent on the pi0 momentum: the pi0 spectrum perpen
Pion and Kaon Electromagnetic Form Factors
Bijnens, J; Bijnens, Johan; Talavera, Pere
2002-01-01
We study the electromagnetic form factor of the pion and kaons at low-energies with the use of Chiral Perturbation Theory. The analysis is performed within the three flavour framework and at next-to-next-to-leading order. We explain carefully all the relevant consistency checks on the expressions, present full analytical results for the pion form factor and describe all the assumptions in the analysis. From the phenomenological point of view we make use of our expression and the available data to obtain the charge radius of the pion obtaining $_V^\\pi=(0.452+-0.013) fm^2$, as well as the low-energy constant $L_9^r(m_\\rho)= (5.93+-0.43)10^{-3}$. We also obtain experimental values for 3 combinations of order $p^6$ constants.
Semiclassical model for pion production by neutrons on nuclei
Sparrow, D A; Sternheim, M M
1974-01-01
A model for pion production by neutrons on nuclei is derived by a straightforward extension of the semiclassical model for pion production by protons, previously described by two of the present authors, Silbar and Sternheim (1973). Both models are then applied to compute pion production cross sections for nucleons incident on Pb, Cu and Al, and pion absorption cross sections in nuclear matter. Results are consistent with (unpublished) experimental data from CERN. (10 refs).
Double radiative pion capture on hydrogen and deuterium and the nucleon's pion cloud
Tripathi, S; Christy, M E; Clark, J H D; Gorringe, T P; Hasinoff, M D; Kovash, M A; Wright, D H; Zolnierczuk, P A
2007-01-01
We report measurements of double radiative capture in pionic hydrogen and pionic deuterium. The measurements were performed with the RMC spectrometer at the TRIUMF cyclotron by recording photon pairs from pion stops in liquid hydrogen and deuterium targets. We obtained absolute branching ratios of $(3.02 \\pm 0.27 (stat.) \\pm 0.31 (syst.)) \\times 10^{-5}$ for hydrogen and $(1.42 \\pm ^{0.09}_{0.12} (stat.) \\pm 0.11 (syst.)) \\times 10^{-5}$ for deuterium, and relative branching ratios of double radiative capture to single radiative capture of $(7.68 \\pm 0.69(stat.) \\pm 0.79(syst.)) \\times 10^{-5}$ for hydrogen and $(5.44 \\pm^{0.34}_{0.46}(stat.) \\pm 0.42(syst.)) \\times 10^{-5}$ for deuterium. For hydrogen, the measured branching ratio and photon energy-angle distributions are in fair agreement with a reaction mechanism involving the annihilation of the incident $\\pi^-$ on the $\\pi^+$ cloud of the target proton. For deuterium, the measured branching ratio and energy-angle distributions are qualitatively consisten...
Pions in the nuclear medium and Drell-Yan scattering
Dieperink, AEL; Korpa, CL
1997-01-01
We investigate the modification of the pion cloud in the nuclear medium and its effect on the nuclear Drell-Yan process. The pion's in-medium self-energy is calculated in a self-consistent delta-hole model, with particle-hole contributions also included. Both the imaginary and real parts of the pion
Energy Technology Data Exchange (ETDEWEB)
Airapetian, A. [Justus-Liebig Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); University of Michigan, Randall Laboratory of Physics, Ann Arbor, MI (United States); Akopov, N.; Elbakian, G.; Gharibyan, V.; Marukyan, H.; Petrosyan, A. [Yerevan Physics Institute, Yerevan (Armenia); Akopov, Z.; Borissov, A.; Deconinck, W.; Holler, Y.; Rostomyan, A.; Zihlmann, B. [DESY, Hamburg (Germany); Aschenauer, E.C.; Nowak, W.D. [DESY, Zeuthen (Germany); Augustyniak, W.; Marianski, B.; Trzcinski, A.; Zupranski, P. [National Centre for Nuclear Research, Warsaw (Poland); Belostotski, S.; Kisselev, A.; Manaenkov, S.I.; Veretennikov, D.; Vikhrov, V. [B.P. Konstantinov Petersburg Nuclear Physics Institute, Leningrad Region (Russian Federation); Blok, H.P. [National Institute for Subatomic Physics (Nikhef), Amsterdam (Netherlands); VU University, Department of Physics and Astronomy, Amsterdam (Netherlands); Bryzgalov, V.; Ivanilov, A.; Korotkov, V.; Salomatin, Y. [Institute for High Energy Physics, Moscow Region (Russian Federation); Capitani, G.P.; De Sanctis, E.; Muccifora, V.; Reolon, A.R. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, Frascati (Italy); Ciullo, G.; Lenisa, P.; Pappalardo, L.L.; Statera, M. [Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Ferrara (Italy); Universita di Ferrara, Dipartimento di Fisica e Scienze della Terra, Ferrara (Italy); Contalbrigo, M. [Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Ferrara (Italy); De Leo, R.; Lagamba, L.; Vilardi, I. [Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Bari (Italy); Dueren, M. [Justus-Liebig Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Ellinghaus, F. [University of Colorado, Nuclear Physics Laboratory, Boulder, CO (United States); Felawka, L. [TRIUMF, Vancouver, BC (Canada); Frullani, S.; Garibaldi, F. [Istituto Nazionale di Fisica Nucleare, Sezione di Roma, Gruppo Collegato Sanita, Rome (Italy); Istituto Superiore di Sanita, Rome (Italy); Gavrilov, G. [DESY, Hamburg (Germany); B.P. Konstantinov Petersburg Nuclear Physics Institute, Leningrad Region (Russian Federation); TRIUMF, Vancouver, BC (Canada); Goloskokov, S.V.; Shutov, V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Jackson, H.E.; Reimer, P.E. [Argonne National Laboratory, Physics Division, Argonne, IL (United States); Joosten, S. [Ghent University, Department of Physics and Astronomy, Gent (Belgium); University of Illinois, Department of Physics, Urbana, IL (United States); Kaiser, R.; Lehmann, I.; Rosner, G.; Seitz, B. [University of Glasgow, SUPA, School of Physics and Astronomy, Glasgow (United Kingdom); Karyan, G. [DESY, Hamburg (Germany); Yerevan Physics Institute, Yerevan (Armenia); Kozlov, V.; Terkulov, A. [Lebedev Physical Institute, Moscow (Russian Federation); Kravchenko, P. [Universitaet Erlangen-Nuernberg, Physikalisches Institut, Erlangen (Germany); B.P. Konstantinov Petersburg Nuclear Physics Institute, Leningrad Region (Russian Federation); Kroll, P.; Schaefer, A. [Universitaet Regensburg, Institut fuer Theoretische Physik, Regensburg (Germany); Lapikas, L. [National Institute for Subatomic Physics (Nikhef), Amsterdam (Netherlands); Lorenzon, W. [University of Michigan, Randall Laboratory of Physics, Ann Arbor, MI (United States); Miyachi, Y.; Shibata, T.A. [Tokyo Institute of Technology, Department of Physics, Tokyo (Japan); Movsisyan, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara, Ferrara (Italy); Yerevan Physics Institute, Yerevan (Armenia); Nass, A.; Rith, K. [Universitaet Erlangen-Nuernberg, Physikalisches Institut, Erlangen (Germany); Riedl, C. [DESY, Zeuthen (Germany); University of Illinois, Department of Physics, Urbana, IL (United States); Ryckbosch, D.; Tytgat, M.; Haarlem, Y. van [Ghent University, Department of Physics and Astronomy, Gent (Belgium); Schnell, G. [University of the Basque Country UPV/EHU, Department of Theoretical Physics, Bilbao (Spain); Basque Foundation for Science, IKERBASQUE, Bilbao (Spain); Ghent University, Department of Physics and Astronomy, Gent (Belgium); Truty, R. [University of Illinois, Department of Physics, Urbana, IL (United States)
2017-06-15
Exclusive ρ{sup 0}-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV{sup 2} < Q{sup 2} < 7.0 GeV{sup 2}, 3.0 GeV < W < 6.3 GeV, and -t{sup '} < 0.4 GeV{sup 2}. Using an unbinned maximum-likelihood method, 25 parameters are extracted. These determine the real and imaginary parts of the ratios of several helicity amplitudes describing ρ{sup 0}-meson production by a virtual photon. The denominator of those ratios is the dominant amplitude, the nucleon-helicity-non-flip amplitude F{sub 0(1)/(2)0(1)/(2)}, which describes the production of a longitudinal ρ{sup 0}-meson by a longitudinal virtual photon. The ratios of nucleon-helicity-non-flip amplitudes are found to be in good agreement with those from the previous HERMES analysis. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to F{sub 0(1)/(2)0(1)/(2)}. Results obtained in a handbag approach based on generalized parton distributions taking into account the contribution from pion exchange are found to be in good agreement with these ratios. Within the model, the data favor a positive sign for the π - ρ transition form factor. By also exploiting the longitudinal beam polarization, a total of 71 ρ{sup 0} spin-density matrix elements is determined from the extracted 25 parameters, in contrast to only 53 elements as directly determined in earlier analyses. (orig.)
Proton-pion and two-pion correlations in eA interactions
Energy Technology Data Exchange (ETDEWEB)
Degtyarenko, P.V. [ITEP, Moscow (Russian Federation); Doroshkevich, E.A. [ITEP, Moscow (Russian Federation); Kurzenkov, A.A. [ITEP, Moscow (Russian Federation); Leksin, G.A. [ITEP, Moscow (Russian Federation); Stavinsky, A.V. [ITEP, Moscow (Russian Federation); Vlassov, A.V. [ITEP, Moscow (Russian Federation)
1997-05-01
We report here the results on studying of proton-pion and two-pion correlations in eA interactions at 5 GeV. Kinematic correlations were studied as a function of the two-particle opening angle, their momenta and proton multiplicity. The universal properties of correlation functions were found with respect to different particle species. Interferometry method was used to determine the size of the interaction region. (orig.). With 2 figs.
Pion scattering and electro-production on nucleons in the resonance region in chiral quark models
Sirca, Simon; Fiolhais, Manuel; Alberto, Pedro
2011-01-01
Pion scattering and electro-production amplitudes have been computed in a coupled-channel framework incorporating quasi-bound quark-model states, based on the Cloudy Bag model. All relevant low-lying nucleon resonances in the P33, P11, and S11 partial waves have been covered, including the Delta(1232), the N*(1440), N*(1535), and N*(1650). Consistent results have been obtained for elastic and inelastic scattering (two-pion, eta-N, and K-Lambda channels), as well as for electro-production. The meson cloud has been shown to play a major role, in particular in electro-magnetic observables in the P33 and P11 channels.
Two-pion exchange nucleon-nucleon potential: relativistic chiral expansion
Higa, R
2003-01-01
We present a relativistic procedure for the chiral expansion of the two-pion exchange component of the $NN$ potential, which emphasizes the role of intermediate $\\pi N$ subamplitudes. The relationship between power counting in $\\pi N$ and $NN$ processes is discussed and results are expressed directly in terms of observable subthreshold coefficients. Interactions are determined by one and two-loop diagrams, involving pions, nucleons and other degrees of freedom, frozen into empirical subthreshold coefficients. The full evaluation of these diagrams produces amplitudes containing many different loop integrals. Their simplification by means of relations among these integrals leads to a set of intermediate results. Subsequent truncation to $O(q^4)$ yields the relativistic potential, which depends on five loop integrals, representing bubble, triangle, crossed box and box diagrams. The bubble and triangle integrals are the same as in $\\pi N$ scattering and we have shown that they also determine the chiral structures...
Distorted waves in pion- (Kaon-) nucleus reactions
Energy Technology Data Exchange (ETDEWEB)
Siciliano, E.R.; Thaler, R.M.
1978-10-02
The difference between the Schroedinger and Klein-Gordon wave functions is calculated for 100--200-MeV pions. The same optical-model potential is used in each case. The differences in the distorted waves so calculated are shown to be significant even though the elastic scattering phase shifts re nearly identical.
Isospin violation in pion-kaon scattering
Kubis, B; Kubis, Bastian; Mei{\\ss}ner, Ulf-G.
2002-01-01
We consider strong and electromagnetic isospin violation in near-threshold pion-kaon scattering. At tree level, such effects are small for all physical channels. We work out the complete one-loop corrections to the process pi^- K^+ -> pi^0 K^0. They come out rather small. We also show that the corresponding radiative cross section is highly suppressed at threshold.
Pion decay constants in dense skyrmion matter
Directory of Open Access Journals (Sweden)
Lee H.-J.
2010-10-01
Full Text Available According to the QCD, the hadronic matter can have various phases with matter density and temperature. In general, when there is phase transition in a matter, it is known that a symmetry in the matter changes. In case of the hadronic matter, the chiral symmetry in the matter is expected to be restored when the matter density (or temperature increases. The actual order parameter with respect to the chiral symmetry in the hadronic matter is known as the quark condensate from the QCD, but the pion decay constant, corresponding to the radius of the chiral circle, plays the role of the order parameter in an eﬀective ﬁeld theoretical approach to the QCD. In this paper, by using the skyrmion model which is an eﬀective theory to the QCD, we construct the skyrmion matter as a model of the hadronic matter (nuclear matter and calculate the pion decay constant in the matter. Because of presence of the matter, the pion decay constant is split into the two components, the temporal component and the spatial component. We discuss the phase transition in the skyrmion matter and behavior of the two components of the decay constant for massless pion with density of the skyrmion matter.
Measurement of the Charged-Pion Polarizability
Adolph, C; Alexeev, M.G.; Alexeev, G.D.; Amoroso, A.; Andrieux, V.; Anosov, V.; Austregesilo, A.; Badelek, B.; Balestra, F.; Barth, J.; Baum, G.; Beck, R.; Bedfer, Y.; Berlin, A.; Bernhard, J.; Bicker, K.; Bieling, J.; Birsa, R.; Bisplinghoff, J.; Bodlak, M.; Boer, M.; Bordalo, P.; Bradamante, F.; Braun, C.; Bressan, A.; Buchele, M.; Burtin, E.; Capozza, L.; Chiosso, M.; Chung, S.U.; Cicuttin, A.; Colantoni, M.; Crespo, M.L.; Curiel, Q.; Dalla Torre, S.; Dasgupta, S.S.; Dasgupta, S.; Denisov, O.Yu.; Dinkelbach, A.M.; Donskov, S.V.; Doshita, N.; Duic, V.; Dunnweber, W.; Dziewiecki, M.; Efremov, A.; Elia, C.; Eversheim, P.D.; Eyrich, W.; Faessler, M.; Ferrero, A.; Filin, A.; Finger, M.; M. Finger jr; Fischer, H.; Franco, C.; von Hohenesche, N. du Fresne; Friedrich, J.M.; Frolov, V.; Gautheron, F.; Gavrichtchouk, O.P.; Gerassimov, S.; Geyer, R.; Gnesi, I.; Gobbo, B.; Goertz, S.; Gorzellik, M.; Grabmuller, S.; Grasso, A.; Grube, B.; Grussenmeyer, T.; Guskov, A.; Guthorl, T.; Haas, F.; von Harrach, D.; Hahne, D.; Hashimoto, R.; Heinsius, F.H.; Herrmann, F.; Hinterberger, F.; Hoppner, Ch.; Horikawa, N.; d'Hose, N.; Huber, S.; Ishimoto, S.; Ivanov, A.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jary, V.; Jasinski, P.; Jorg, P.; Joosten, R.; Kabuss, E.; Ketzer, B.; Khaustov, G.V.; Khokhlov, Yu. A.; Kisselev, Yu.; Klein, F.; Klimaszewski, K.; Koivuniemi, J.H.; Kolosov, V.N.; Kondo, K.; Konigsmann, K.; Konorov, I.; Konstantinov, V.F.; Kotzinian, A.M.; Kouznetsov, O.; Kramer, M.; Kroumchtein, Z.V.; Kuchinski, N.; Kuhn, R.; Kunne, F.; Kurek, K.; Kurjata, R.P.; Lednev, A.A.; Lehmann, A.; Levillain, M.; Levorato, S.; Lichtenstadt, J.; Maggiora, A.; Magnon, A.; Makke, N.; Mallot, G.K.; Marchand, C.; Martin, A.; Marzec, J.; Matousek, J.; Matsuda, H.; Matsuda, T.; Meshcheryakov, G.; Meyer, W.; Michigami, T.; Mikhailov, Yu. V.; Miyachi, Y.; Moinester, M.A.; Nagaytsev, A.; Nagel, T.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V.I.; Novy, J.; Nowak, W.D.; Nunes, A.S.; Olshevsky, A.G.; Orlov, I.; Ostrick, M.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Peshekhonov, D.; Platchkov, S.; Pochodzalla, J.; Polyakov, V.A.; Pretz, J.; Quaresma, M.; Quintans, C.; Ramos, S.; Regali, C.; Reicherz, G.; Rocco, E.; Rossiyskaya, N.S.; Ryabchikov, D.I.; Rychter, A.; Samoylenko, V.D.; Sandacz, A.; Sarkar, S.; Savin, I.A.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schluter, T.; Schmidt, K.; Schmieden, H.; Schonning, K.; Schopferer, S.; Schott, M.; Shevchenko, O.Yu.; Silva, L.; Sinha, L.; Sirtl, S.; Slunecka, M.; Sosio, S.; Sozzi, F.; Srnka, A.; Steiger, L.; Stolarski, M.; Sulc, M.; Sulej, R.; Suzuki, H.; Szabelski, A.; Szameitat, T.; Sznajder, P.; Takekawa, S.; Wolbeek, J. ter; Tessaro, S.; Tessarotto, F.; Thibaud, F.; Uhl, S.; Uman, I.; Virius, M.; Wang, L.; Weisrock, T.; Wilfert, M.; Windmolders, R.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zink, A.
2015-01-01
The COMPASS collaboration at CERN has investigated pion Compton scattering, $\\pi^-\\gamma\\rightarrow \\pi^-\\gamma$, at centre-of-mass energy below 3.5 pion masses. The process is embedded in the reaction $\\pi^-\\mathrm{Ni}\\rightarrow\\pi^-\\gamma\\;\\mathrm{Ni}$, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, $Q^2<0.0015$ (GeV/$c$)$^2$. From a sample of 63 000 events the pion electric polarisability is determined to be $\\alpha_\\pi = (2.0 \\pm 0.6_{\\mbox{stat}} \\pm 0.7_{\\mbox{syst}}) \\times 10^{-4} \\mbox{fm}^3$ under the assumption $\\alpha_\\pi=-\\beta_\\pi$, which relates the electric and magnetic dipole polarisabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction, that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is fou...
High purity pion beam at TRIUMF
Energy Technology Data Exchange (ETDEWEB)
Aguilar-Arevalo, A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Blecher, M. [Physics Department, Virginia Tech., Blacksburg, VA 24061 (United States); Bryman, D.A. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Comfort, J. [Arizona State University, Tempe, AZ 85287 (United States); Doornbos, J.; Doria, L. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Hussein, A. [University of Northern British Columbia, Prince George, BC, V2N 4Z9 (Canada); Ito, N. [Physics Department, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Kettell, S. [Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Kurchaninov, L. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Malbrunot, C. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Marshall, G.M. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Numao, T. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada)], E-mail: toshio@triumf.ca; Poutissou, R.; Sher, A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Walker, B. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Yamada, K. [Physics Department, Osaka University, Toyonaka, Osaka 560-0043 (Japan)
2009-10-11
An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay {pi}{sup +}{yields}e{sup +}{nu} is also described.
High Purity Pion Beam at TRIUMF
Energy Technology Data Exchange (ETDEWEB)
Kettell, S.; Kettell, S.; Aguilar-Arevalo, A.; Blecher, M.; Bryman, D.A.; Comfort, J.; Doornbos, J.; Doria, L.; Hussein, A.; Ito, N.; et al.
2009-10-11
An extension of the TRIUMF M13 low-energy pion channel designed to suppress positrons based on an energy-loss technique is described. A source of beam channel momentum calibration from the decay {pi}{sup +} {yields} e{sup +}{nu} is also described.
Probing neutron-proton dynamics by pions
Ikeno, Natsumi; Nara, Yasushi; Ohnishi, Akira
2016-01-01
In order to investigate the nuclear symmetry energy at high density, we study the pion production in central collisions of neutron-rich nuclei ${}^{132}\\mathrm{Sn}+{}^{124}\\mathrm{Sn}$ at 300 MeV/nucleon using a new approach by combining the antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and $\\Delta$ resonances in the reaction process are handled by JAM. We see the mechanism how the $\\Delta$ resonance and pions are produced reflecting the dynamics of neutrons and protons. We also investigate the impacts of cluster correlations as well as of the high-density symmetry energy on the nucleon dynamics and consequently on the pion ratio. We find that the $\\Delta^-/\\Delta^{++}$ production ratio agrees very well with the neutron-proton squared ratio $(N/Z)^2$ in the high-density and high-momentum region. We show quantitatively that $\\Delta$ production ratio, and therefore $(N/Z)^2$, are directly reflected in the $\\pi^-...
Electroexcitation of nucleon resonances from CLAS data on single pion electroproduction
Energy Technology Data Exchange (ETDEWEB)
I. G. Aznauryan, V. D. Burkert
2009-11-01
We present results on the electroexcitation of the low mass resonances Delta(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 in a wide range of Q2. The results were obtained in the comprehensive analysis of JLab-CLAS data on differential cross sections, longitudinally polarized beam asymmetries, and longitudinal target and beam-target asymmetries for pion electroproduction off the proton. The data were analysed using two conceptually different approaches, fixed-t dispersion relations and a unitary isobar model, allowing us to draw conclusions on the model sensitivity of the obtained electrocoupling amplitudes. The amplitudes for the Delta(1232)P33} show the importance of a meson-cloud contribution to quantitatively explain the magnetic dipole strength, as well as the electric and scalar quadrupole transitions. They do not show any tendency of approaching the pQCD regime for Q2<6 GeV2. For the Roper resonance, N(1440)P11, the data provide strong evidence for this state as a predominantly radial excitation of a 3-quark ground state. Measured in pion electroproduction, the transverse helicity amplitude for the N(1535)S11 allowed us to obtain the branching ratios of this state to the piN and etaN channels via comparison to the results extracted from eta electroproduction. The extensive CLAS data also enabled the extraction of the gamma*p -> N(1520)D13 and N(1535)S11 longitudinal helicity amplitudes with good precision.
Pion absorption processes. [32 to 74 MeV
Energy Technology Data Exchange (ETDEWEB)
Doss, K G.R.
1980-04-01
Proton and deuteron production from low-energy pion absorption in light nuclei leading to discrete and continuum states were measured. The LEP beam line at LAMPF was used with a stack of 8 intrinsic germanium crystals. The proton energy spectra are in general characterized by a broad bump at an energy approximately corresponding to ..pi../sup +/d ..-->.. pp reaction kinematics, suggestive of pion absorption on 2 nucleons. The energy-integrated cross-section for production of deuterons has an angular distribution similar to that for production of protons. The dependence of the total pion absorption cross-section on A is explained using a semi-classical model for pion transport in nuclei. The (..pi../sup +/,p) as well as (..pi../sup +/,d) reactions generally favor transitions involving larger angular momentum transfer to the residual nucleus when states of similar nuclear structure are considered. The low-energy excitation spectra from the (..pi../sup +/,p) reaction are similar to the spectra from (p,d) reaction on /sup 12/C and /sup 13/C. However, a calculation of the (..pi.. = ,p) cross-section using the measured (p,d) reaction with the formulation of Wilkin to relate the two reactions is in moderate disagreement with the measured (..pi../sup +/,p) cross-sections. The excitation spectra from the (..pi../sup +/,p) reaction indicte the importance of two-step processes for the reaction. The (..pi../sup +/,d) reaction leading to the ground state of -- residual nucleus has been seen for /sup 7/Li, /sup 12/C, and /sup 13/C targets. The measured cross section for the /sup 12/C(..pi../sup +/,d)/sup 10/C reaction to the 2/sup +/ state is much higher than that for the ground state. For the case of /sup 18/O, no counts were seen for excitation energy of < 10 MeV, at a sensitivity of approx. 100 nb/sr count. These features indicate a possible failure of the model of Betz and Kerman for the (..pi../sup +/,d) reaction.
The pion: an enigma within the Standard Model
Horn, Tanja
2016-01-01
Almost 50 years after the discovery of gluons & quarks, we are only just beginning to understand how QCD builds the basic bricks for nuclei: neutrons, protons, and the pions that bind them. QCD is characterised by two emergent phenomena: confinement & dynamical chiral symmetry breaking (DCSB). They are expressed with great force in the character of the pion. In turn, pion properties suggest that confinement & DCSB are closely connected. As both a Nambu-Goldstone boson and a quark-antiquark bound-state, the pion is unique in Nature. Developing an understanding of its properties is thus critical to revealing basic features of the Standard Model. We describe experimental progress in this direction, made using electromagnetic probes, highlighting both improvements in the precision of charged-pion form factor data, achieved in the past decade, and new results on the neutral-pion transition form factor. Both challenge existing notions of pion structure. We also provide a theoretical context for these em...
Modified π π amplitude with σ pole
Bydžovský, P.; Kamiński, R.; Nazari, V.
2014-12-01
A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (π π , K K ¯, and η η ) and P (π π , ρ 2 π , and ρ σ ) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the π π threshold region. Moreover, the pole of the S wave amplitude related with the f0(500 ) meson (former f0(600 ) or σ ) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the σ pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, π π amplitudes with a heavy and broad σ meson without changing of their original mathematical structure.
Benchmark Analysis of Pion Contribution from Galactic Cosmic Rays
Aghara, Sukesh K.; Blattnig, Steve R.; Norbury, John W.; Singleterry, Robert C., Jr.
2008-01-01
Shielding strategies for extended stays in space must include a comprehensive resolution of the secondary radiation environment inside the spacecraft induced by the primary, external radiation. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. A systematic verification and validation effort is underway for HZETRN, which is a space radiation transport code currently used by NASA. It performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. The question naturally arises as to what is the contribution of these particles to space radiation. The pion has a production kinetic energy threshold of about 280 MeV. The Galactic cosmic ray (GCR) spectra, coincidentally, reaches flux maxima in the hundreds of MeV range, corresponding to the pion production threshold. We present results from the Monte Carlo code MCNPX, showing the effect of lepton and meson physics when produced and transported explicitly in a GCR environment.
Asymptotic Behaviour of Pion--Pion Total Cross--Sections
Greynat, David; Vulvert, Grégory
2014-01-01
We derive a sum rule which shows an inconsistency between the Lukaszuk-Martin coefficient of the Froissart-Martin bound and well known properties of $\\pi\\pi$ amplitudes in QCD. We next compute the total cross sections for $\\pi^+ \\pi^-$, $\\pi^{\\pm} \\pi^0$ and $\\pi^0 \\pi^0$ scattering within the framework of the constituent chiral quark model (C$\\chi$QM) in the limit of a large number of colours $\\mathrm{N_c}$ and discuss their asymptotic behaviours. The same $\\pi\\pi$ cross sections are also discussed within the general framework of Large-$\\mathrm{N_c}$ QCD and we show that it is possible to make an Ansatz for the isospin $I=1$ and $I=0$ spectrum which satisfy the Froissart-Martin bound with coefficients which, contrary to the Lukaszuk-Martin coefficient, are not singular in the chiral limit and have the correct Large-$\\mathrm{N_c}$ counting. We finally propose a simple phenomenological model which matches the low energy behaviours of the $\\sigma_{\\pi^{\\pm}\\pi^0}^{\\rm total}(s)$ cross section predicted by the C...
Connecting physical resonant amplitudes and lattice QCD
Bolton, Daniel R; Wilson, David J
2015-01-01
We present a determination of the isovector, $P$-wave $\\pi\\pi$ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using $m_\\pi =236$ MeV. The finite volume spectra are described using extensions of L\\"uscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at $m_\\pi= 140$ MeV. The scattering phase shift is found to be in good agreement with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a $\\rho$-resonance pole at $E_\\rho= \\left[755(2)(1)(^{20}_{02})-\\frac{i}{2}\\,129(3)(1)(^{7}_{1})\\right]~{\\rm MeV}$. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.
Kondratyuk, S; Kubodera, K; Myhrer, F; Scholten, O
2004-01-01
The Adler-Weisberger and Goldberger-Miyazawa-Oehme sum rules are calculated within a relativistic, unitary and crossing symmetric dynamical model for pion-nucleon scattering using two different methods: (1) by evaluating the scattering amplitude at the corresponding low-energy kinematics and (2) by
Wolcott, J; Altinok, O; Bercellie, A; Betancourt, M; Bodek, A; Bravar, A; Budd, H; Cai, T; Carneiro, M F; Chvojka, J; Devan, J; Dytman, S A; Diaz, G A; Eberly, B; Endress, E; Felix, J; Fields, L; Galindo, R; Gallagher, H; Golan, T; Gran, R; Harris, D A; Higuera, A; Hurtado, K; Kiveni, M; Kleykamp, J; Kordosky, M; Le, T; Maher, E; Manly, S; Mann, W A; Marshall, C M; Caicedo, D A Martinez; McFarland, K S; McGivern, C L; McGowan, A M; Messerly, B; Miller, J; Mislivec, A; Morfin, J G; Mousseau, J; Naples, D; Nelson, J K; Norrick, A; Nuruzzaman,; Paolone, V; Park, J; Patrick, C E; Perdue, G N; Rakotondravohitra, L; Ramirez, M A; Ray, H; Ren, L; Rimal, D; Rodrigues, P A; Ruterbories, D; Schellman, H; Schmitz, D W; Salinas, C J Solano; Sanchez, S F; Tagg, N; Tice, B G; Valencia, E; Walton, T; Wospakrik, M; Zhang, D
2016-01-01
The MINERvA experiment observes an excess of events containing electromagnetic showers relative to the expectation from Monte Carlo simulations in neutral-current neutrino interactions with mean beam energy of 4.5 GeV on a hydrocarbon target. The excess is characterized and found to be consistent with neutral-current neutral pion production with a broad energy distribution peaking at 7 GeV and a total cross section of 0.26 +- 0.02 (stat) +- 0.08 (sys) x 10^{-39} cm^{2}. The angular distribution, electromagnetic shower energy, and spatial distribution of the energy depositions of the excess are consistent with expectations from neutrino neutral-current diffractive neutral pion production from hydrogen in the hydrocarbon target. These data comprise the first direct experimental observation and constraint for a reaction that poses an important background process in neutrino oscillation experiments searching for muon neutrino to electron neutrino oscillations.
Vector meson condensation in a pion superfluid
Brauner, Tomáš; Huang, Xu-Guang
2016-11-01
We revisit the suggestion that charged ρ -mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that ρ -meson condensation is either avoided or postponed to isospin chemical potentials much higher than the ρ -meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and ρ -mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.
Pion contamination in the MICE muon beam
Bogomilov, M.; Vankova-Kirilova, G.; Bertoni, R.; Bonesini, M.; Chignoli, F.; Mazza, R.; Palladino, V.; de Bari, A.; Cecchet, G.; Capponi, M.; Iaciofano, A.; Orestano, D.; Pastore, F.; Tortora, L.; Kuno, Y.; Sakamoto, H.; Ishimoto, S.; Japan, Ibaraki; Filthaut, F.; Hansen, O.M.; Ramberger, S.; Vretenar, M.; Asfandiyarov, R.; Blondel, A.; Drielsma, F.; Karadzhov, Y.; Charnley, G.; Collomb, N.; Gallagher, A.; Grant, A.; Griffiths, S.; Hartnett, T.; Martlew, B.; Moss, A.; Muir, A.; Mullacrane, I.; Oates, A.; Owens, P.; Stokes, G.; Warburton, P.; White, C.; Adams, D.; Barclay, P.; Bayliss, V.; Bradshaw, T.W.; Courthold, M.; Francis, V.; Fry, L.; Hayler, T.; Hills, M.; Lintern, A.; Macwaters, C.; Nichols, A.; Preece, R.; Ricciardi, S.; Rogers, C.; Stanley, T.; Tarrant, J.; Watson, S.; Wilson, A.; Bayes, R.; Nugent, J.C.; Soler, F.J.P.; Cooke, P.; Gamet, R.; Alekou, A.; Apollonio, M.; Barber, G.; Colling, D.; Dobbs, A.; Dornan, P.; Hunt, C.; Lagrange, J-B.; Long, K.; Martyniak, J.; Middleton, S.; Pasternak, J.; Santos, E.; Savidge, T.; Uchida, M.A.; Blackmore, V.J.; Carlisle, T.; Cobb, J.H.; Lau, W.; Rayner, M.A.; Tunnell, C.D.; Booth, C.N.; Hodgson, P.; Langlands, J.; Nicholson, R.; Overton, E.; Robinson, M.; Smith, P.J.; Dick, A.; Ronald, K.; Speirs, D.; Whyte, C.G.; Young, A.; Boyd, S.; Franchini, P.; Greis, J.R.; Pidcott, C.; Taylor, I.; Gardener, R.; Kyberd, P.; Littlefield, M.; Nebrensky, J.J.; Bross, A.D.; Fitzpatrick, T.; Leonova, M.; Moretti, A.; Neuffer, D.; Popovic, M.; Rubinov, P.; Rucinski, R.; Roberts, T.J.; Bowring, D.; DeMello, A.; Gourlay, S.; Li, D.; Prestemon, S.; Virostek, S.; Zisman, M.; Drews, M.; Hanlet, P.; Kafka, G.; Kaplan, D.M.; Rajaram, D.; Snopok, P.; Torun, Y.; Winter, M.; Blot, S.; Kim, Y.K.; Bravar, U.; Onel, Y.; Cremaldi, L.M.; Hart, T.L.; Luo, T.; Sanders, D.A.; Summers, D.J.; Cline, D.; Yang, X.; Coney, L.; Hanson, G.G.; Heidt, C.
2016-01-01
The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240\\,MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than $\\sim$1\\% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is $f_\\pi < 1.4\\%$ at 90\\% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.
Pion mean fields and heavy baryons
Yang, Ghil-Seok; Polyakov, Maxim V; Praszałowicz, Michał
2016-01-01
We show that the masses of the lowest-lying heavy baryons can be very well described in a pion mean-field approach. We consider a heavy baryon as a system consisting of the $N_c-1$ light quarks that induce the pion mean field, and a heavy quark as a static color source under the influence of this mean field. In this approach we derive a number of \\textit{model-independent} relations and calculate the heavy baryon masses using those of the lowest-lying light baryons as input. The results are in remarkable agreement with the experimental data. In addition, the mass of the $\\Omega_b^*$ baryon is predicted.
Vector meson condensation in a pion superfluid
Brauner, Tomas
2016-01-01
We revisit the suggestion that charged rho-mesons undergo Bose-Einstein condensation in isospin-rich nuclear matter. Using a simple version of the Nambu-Jona-Lasinio (NJL) model, we conclude that rho-meson condensation is either avoided or postponed to isospin chemical potentials much higher than the rho-meson mass as a consequence of the repulsive interaction with the preformed pion condensate. In order to support our numerical results, we work out a linear sigma model for pions and rho-mesons, showing that the two models lead to similar patterns of medium dependence of meson masses. As a byproduct, we analyze in detail the mapping between the NJL model and the linear sigma model, focusing on conditions that must be satisfied for a quantitative agreement between the models.
Pion contamination in the MICE muon beam
Adams, D.; Alekou, A.; Apollonio, M.; Asfandiyarov, R.; Barber, G.; Barclay, P.; de Bari, A.; Bayes, R.; Bayliss, V.; Bertoni, R.; Blackmore, V. J.; Blondel, A.; Blot, S.; Bogomilov, M.; Bonesini, M.; Booth, C. N.; Bowring, D.; Boyd, S.; Brashaw, T. W.; Bravar, U.; Bross, A. D.; Capponi, M.; Carlisle, T.; Cecchet, G.; Charnley, C.; Chignoli, F.; Cline, D.; Cobb, J. H.; Colling, G.; Collomb, N.; Coney, L.; Cooke, P.; Courthold, M.; Cremaldi, L. M.; DeMello, A.; Dick, A.; Dobbs, A.; Dornan, P.; Drews, M.; Drielsma, F.; Filthaut, F.; Fitzpatrick, T.; Franchini, P.; Francis, V.; Fry, L.; Gallagher, A.; Gamet, R.; Gardener, R.; Gourlay, S.; Grant, A.; Greis, J. R.; Griffiths, S.; Hanlet, P.; Hansen, O. M.; Hanson, G. G.; Hart, T. L.; Hartnett, T.; Hayler, T.; Heidt, C.; Hills, M.; Hodgson, P.; Hunt, C.; Iaciofano, A.; Ishimoto, S.; Kafka, G.; Kaplan, D. M.; Karadzhov, Y.; Kim, Y. K.; Kuno, Y.; Kyberd, P.; Lagrange, J.-B.; Langlands, J.; Lau, W.; Leonova, M.; Li, D.; Lintern, A.; Littlefield, M.; Long, K.; Luo, T.; Macwaters, C.; Martlew, B.; Martyniak, J.; Mazza, R.; Middleton, S.; Moretti, A.; Moss, A.; Muir, A.; Mullacrane, I.; Nebrensky, J. J.; Neuffer, D.; Nichols, A.; Nicholson, R.; Nugent, J. C.; Oates, A.; Onel, Y.; Orestano, D.; Overton, E.; Owens, P.; Palladino, V.; Pasternak, J.; Pastore, F.; Pidcott, C.; Popovic, M.; Preece, R.; Prestemon, S.; Rajaram, D.; Ramberger, S.; Rayner, M. A.; Ricciardi, S.; Roberts, T. J.; Robinson, M.; Rogers, C.; Ronald, K.; Rubinov, P.; Rucinski, P.; Sakamato, H.; Sanders, D. A.; Santos, E.; Savidge, T.; Smith, P. J.; Snopok, P.; Soler, F. J. P.; Speirs, D.; Stanley, T.; Stokes, G.; Summers, D. J.; Tarrant, J.; Taylor, I.; Tortora, L.; Torun, Y.; Tsenov, R.; Tunnell, C. D.; Uchida, M. A.; Vankova-Kirilova, G.; Virostek, S.; Vretenar, M.; Warburton, P.; Watson, S.; White, C.; Whyte, C. G.; Wilson, A.; Winter, M.; Yang, X.; Young, A.; Zisman, M.
2016-03-01
The international Muon Ionization Cooling Experiment (MICE) will perform a systematic investigation of ionization cooling with muon beams of momentum between 140 and 240 MeV/c at the Rutherford Appleton Laboratory ISIS facility. The measurement of ionization cooling in MICE relies on the selection of a pure sample of muons that traverse the experiment. To make this selection, the MICE Muon Beam is designed to deliver a beam of muons with less than ~1% contamination. To make the final muon selection, MICE employs a particle-identification (PID) system upstream and downstream of the cooling cell. The PID system includes time-of-flight hodoscopes, threshold-Cherenkov counters and calorimetry. The upper limit for the pion contamination measured in this paper is fπ < 1.4% at 90% C.L., including systematic uncertainties. Therefore, the MICE Muon Beam is able to meet the stringent pion-contamination requirements of the study of ionization cooling.
Loop corrections to pion and kaon neutrinoproduction
Siddikov, Marat
2016-01-01
In this paper we study the next-to-leading order corrections to deeply virtual pion and kaon production in neutrino experiments. We estimate these corrections in the kinematics of the Minerva experiment at FERMILAB, and find that they are sizable and increase the leading order cross-section by up to a factor of two. We provide a code, which can be used for the evaluation of the cross-sections, taking into account these corrections and employing various GPD models.
Pion production in neutrino interactions with nuclei
Leitner, T; Buss, O; Mosel, U; Alvarez-Ruso, L
2009-01-01
Neutrino-induced pion production on nuclear targets is the major inelastic channel in all present-day neutrino-oscillation experiments. It has to be understood quantitatively in order to be able to reconstruct the neutrino-energy at experiments such as MiniBooNE or K2K and T2K. We report here results of calculations cross sections for both this channel and for quasielastic scattering within the semiclassical GiBUU method. This methods contains scattering, both elastic and inelastic, absorption and side-feeding of channels all in a unitary, common theoretical framework and code. We find that charged current quasielastic scattering (CCQE) and $1 \\pi$ production are closely entangled in actual experiments, due to final state interactions of the scattered nucleons on one hand and of the $\\Delta$ resonances and pions, on the other hand. We discuss the uncertainties in the elementary pion production cross sections from ANL and BNL. We find the surprising result that the recent $1 \\pi$ production cross section data ...
The transverse structure of the pion in momentum space inspired by the AdS/QCD correspondence
Bacchetta, Alessandro; Cotogno, Sabrina; Pasquini, Barbara
2017-08-01
We study the internal structure of the pion using a model inspired by the AdS/QCD correspondence. The holographic approach provides the light-front wave function (LFWF) for the leading Fock-state component of the pion. We adopt two different forms for the LFWF derived from the AdS/QCD soft-wall model, with free parameters fitted to the available experimental information on the pion electromagnetic form factor and the leading-twist parton distribution function. The intrinsic scale of the model is taken as an additional fit parameter. Within this framework, we provide predictions for the unpolarized transverse momentum dependent parton distribution (TMD), and discuss its property both at the scale of the model and after TMD evolution to higher scales that are relevant for upcoming experimental measurements.
Theory of the scattering of pions from nuclei
Energy Technology Data Exchange (ETDEWEB)
Siciliano, E.R.; Thaler, R.M.
1978-09-15
A nonrelativistic quantum field theoretic formulation of pion--nucleus scattering is presented. A nonrelativistic boson--complex-target Low equation is developed, in which the coupling between the incident boson and target constituent particles is completely general. This development is then particularized to the case where the bosons are pions and the target is a nucleus of A nucleons. Special detailed attention is paid to the case where the pion--nucleon coupling is linear. The pion--nucleus Low equation is decomposed into a finite series of A terms, referred to as a spectator expansion, of which the first term involves one active particle and (a-1) spectators and the higher terms involve an increasingly larger number of active target particles. Within the framework of the nonrelativistic pion--nucleus Low equation, a formal definition of the pion--nucleus optical potential is also given.
Measurement of the charged-pion polarisability at COMPASS
CERN. Geneva
2015-01-01
For more than a decade, COMPASS has been tackling the measurement of the electromagnetic polarizability of the charged pion, which describes the stiffness of the pion against deformation in electromagnetic fields. Previous experiments date back to the 1980's in Serpukhov (Russia), where the Primakoff method for realizing interactions of charged pions with quasi-real photons was first employed. Later also other techniques in photon-nucleon and photon-photon collisions were carried out at different machines. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than the previous results, roughly by a factor two, with the smallest uncertainties realized so far. The pion polarisability is of fundamental interest in the low-energy sector of quantum chromodynamics. It is directly linked to the quark-gluon substructure and dynamics of the pion, the lightest bound system of strong interaction.
A combined study of the pion's static properties and form factors
El-Bennich, B; Frederico, T
2012-01-01
We study consistently the pion's static observables and the elastic and \\gamma*\\gamma -> \\pi^0 transition form factors within a light-front model. Consistency requires that all calculations are performed within a given model with the same and single adjusted length or mass-scale parameter of the associated pion bound-state wave function. Our results agree well with all extent data including recent Belle data on the \\gamma*\\gamma -> \\pi^0 form factor at large q^2, yet the BaBar data on this transition form factor resists a sensible comparison. We relax the initial constraint on the bound-state wave function and show the BaBar data can partially be accommodated. This, however, comes at the cost of a hard elastic form factor not in agreement with experiment. Moreover, the pion charge radius is about 40% smaller than its experimentally determined value. It is argued that a decreasing charge radius produces an ever harder form factor with a bound-state amplitude difficultly reconcilable with soft QCD. We also disc...
Energy Technology Data Exchange (ETDEWEB)
Vladimir Pascalutsa; Marc Vanderhaeghen
2006-01-20
We develop an extension of chiral perturbation theory to the {Delta}(1232)-resonance energy region and apply it to investigate the pion electroproduction off the nucleon (e{sup -} N {yields} e{sup -} N {pi}). We present a complete calculation of this process, in the {Delta}-resonance region, up to next-to-leading order in the {delta}-expansion. At this order, the only free parameters are the three low-energy constants corresponding to the magnetic (M1), electric (E2), and Coulomb (C2) {gamma} N {yields} {Delta} transition strength. After fitting these parameters to a few well-known data, our calculation provides a prediction for observables and multipole amplitudes of pion electroproduction. These results compare favorably with the phenomenological multipole solutions and recent experimental results from MIT-Bates and MAMI. Our prediction for the pion-mass dependence of the {gamma}N{Delta} form factors offers an explanation for the discrepancy between the recent lattice-QCD results and the experimental value for the ''C2/M1 ratio'' at low Q{sup 2}.
Yao, De-Liang; Bernard, V; Epelbaum, E; Gasparyan, A M; Gegelia, J; Krebs, H; Meißner, Ulf-G
2016-01-01
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the $S$- and $P$-partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the $D$ and $F$ waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in ...
Yao, De-Liang; Siemens, D.; Bernard, V.; Epelbaum, E.; Gasparyan, A. M.; Gegelia, J.; Krebs, H.; Meißner, Ulf-G.
2016-05-01
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the S- and P -partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the D and F waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.
Isospin violation in low-energy charged pion-kaon scattering
Kubis, B; Kubis, Bastian; Mei{\\ss}ner, Ulf-G.
2002-01-01
We evaluate the isospin breaking corrections to the scattering amplitude \\pi^- K^+ -> \\pi^- K^+ at threshold in the framework of chiral perturbation theory. This channel is of particular interest for the strong 2S-2P energy level shift in pion-kaon bound states. While a prediction of this level shift is hampered by a large uncertainty in the isoscalar scattering length, we find only a moderate uncertainty of about 3% in the electromagnetic corrections which are relevant for the extraction of the scattering lengths from experiment
Elastic Pion-Nucleon Scattering to $O(p^{3})$ in Heavy Baryon Chiral Perturbation Theory
Mojzis, M
1997-01-01
The elastic pi-N scattering amplitude in the isospin limit is calculated in the framework of heavy baryon chiral perturbation theory, up to the third order. Threshold parameters like scattering lengths, volumes, effective ranges, etc. are compared with data. All relevant low energy constants are fixed from the available pion-nucleon data. A clear improvement in the description of data is observed, when going from the first two orders in the chiral expansion to the third one. The importance of even higher orders is suggested by the result.
Pion Interferometry for Hydrodynamical Expanding Source with a Finite Baryon Density
Institute of Scientific and Technical Information of China (English)
ZHANG Wei-Ning; EFAAF M. J.; WONG Cheuk-Yin; KHALILIASR M.
2004-01-01
We calculate the two-pion correlation function for an expanding hadron source with a finite baryon density. The space-time evolution of the source is described by relativistic hydrodynamics and the Hanbury-Brown-Twiss (HBT) radius is extracted after effects of collective expansion and multiple scattering on the HBT interferometry have been taken into account, using quantum probability amplitudes in a path-integral formalism. We find that this radius is substantially smaller than the HBT radius extracted from the freeze-out configuration.
The pion form factor from analyticity and unitarity
Indian Academy of Sciences (India)
B Ananthanarayan; Irinel Caprini; I Sentitemsu Imsong
2012-11-01
Analyticity and unitarity techniques are employed to estimate Taylor coefficients of the pion electromagnetic form factor at = 0 by exploiting the recently evaluated two-pion contribution to the muon ( − 2) and the phase of the pion electromagnetic form factor in the elastic region, known from scattering by Fermi–Watson theorem and the values of the form factor at several points in the space-like region. Regions in the complex -plane are isolated where the form factor cannot have zeros.
Mean pion multiplicities in Ar+Sc collisions
Naskręt, Michał
2016-01-01
Preliminary results for mean negatively charged pion multiplicities $\\langle \\pi^- \\rangle$ using the $h^-$ method are presented for central Ar+Sc collisions at 13, 19, 30, 40, 75 and 150\\textit{A} GeV/c beam momentum. The data were recorded by the NA61/SHINE detector at the CERN SPS. Starting with rapidity distributions ${dn}/{dy}$ the procedure of obtaining total multiplicities is presented. The mean number of wounded nucleons $\\langle W\\rangle$ extracted from the Glissando MC model is used to calculate the ratio $\\langle \\pi^- \\rangle/\\langle W\\rangle.$ The results are compared to those from other experiments and their dependence on colliding systems and collision energy is discussed.
La Vaissière, C de; Dionisi, C; Foster, B; Ganguli, S N; Gavillet, P; Grossman, P; Kittel, E W; Kluyver, J C; Mazzucato, M; Muirhead, William Hugh; Wolters, G F; Zralek, M
1979-01-01
The authors have investigated the properties of off-shell KK and pp annihilations into pions by using the interactions K/sup -/p to Lambda +pions at 4.2 GeV/c. The properties considered are multiplicities, hadronic temperatures and angular distributions. These properties appear more akin to those of pp annihilations in flight than to that of pp annihilation at rest despite the fact that the annihilation energy is small. (14 refs).
Design and simulation of the nuSTORM pion beamline
Energy Technology Data Exchange (ETDEWEB)
Liu, A., E-mail: aoliu@fnal.gov; Neuffer, D.; Bross, A.
2015-11-21
The nuSTORM (neutrinos from STORed Muons) proposal presents a detailed design for a neutrino facility based on a muon storage ring, with muon decay in the production straight section of the ring providing well defined neutrino beams. The facility includes a primary high-energy proton beam line, a target station with pion production and collection, and a pion beamline for pion transportation and injection into a muon decay ring. The nuSTORM design uses “stochastic injection”, in which pions are directed by a chicane, referred to as the Orbit Combination Section (OCS), into the production straight section of the storage ring. Pions that decay within that straight section provide muons within the circulating acceptance of the ring. The design enables injection without kickers or a separate pion decay transport line. The beam line that the pions traverse before being extracted from the decay ring is referred to as the pion beamline. This paper describes the design and simulation of the pion beamline, and includes full beam dynamics simulations of the system.
A dynamical model for pion electroproduction on the nucleon
Energy Technology Data Exchange (ETDEWEB)
George L. Caia; Louis E. Wright; Vladimir Pascalutsa
2005-06-01
We develop a Lorenz- and gauge-invariant dynamical model for pion electroproduction in the resonance region. The model is based on solving of the Salpeter (instantaneous) equation for the pion-nucleon interaction with a hadron-exchange potential. We find that the one-particle-exchange kernel of the Salpeter equation for pion electroproduction develops an unphysical singularity for a finite value of Q{sup 2}. We analyze two methods of dealing with this problem. Results of our model are compared with recent single-polarization data for pion electroproduction.
Inelastic electron-pion scattering at FNAL (SELEX)
Moinester, M A; Steiner, V; Moinester, Murray A.; Ocherashvili, Aharon; Steiner, Victor
1999-01-01
In this report we describe the analysis status of electron-pion inelastic scattering $\\pi e \\to \\pi' e' \\gamma$ and $\\pi e \\to \\pi' e' \\pi^0$ reaction data, measured in inverse pion-electron scattering at 590 GeV/c at FNAL. The data give information on reactions that were never previously measured: (1) radiative width from a measurement of the transition form factor near zero momentum transfer, (2) $ \\pi e \\to e' \\pi' \\pi^0$ scattering near threshold for a determination of the chiral anomaly transition form factor and the $\\gamma field is Compton scattered on the pion, for a determination of the never previously measured generalized pion polarizabilities.
Energy Technology Data Exchange (ETDEWEB)
Erhardt, Arthur; Clement, Heinz; Doroshkevich, Evgueny; Ehrhardt, Katharina; Wagner, Gerhard J. [Physikalisches Institut der Universitaet Tuebingen (Germany)
2008-07-01
The pp{yields}pp{pi}{sup +}{pi}{sup -} reaction was measured with a polarized proton beam at T{sub p}=750 and 800 MeV using the short version of the COSY-TOF spectrometer. The implementation of a delayed-pulse technique for Quirl and Central Calorimeter provided positive {pi}{sup +} identification in addition to the standard particle identification. Differential cross sections as well as vector analyzing powers have been obtained. They are compared to previous data and theoretical calculations. In contrast to predictions we find large analyzing power values up to A{sub y}=0.3. At these measurements the dominating reaction mechanism is the excitation of the Roper resonance and its decay into the {pi}{sup +}{pi}{sup -} channel either directly or via {delta} excitation. From invariant M{sub {pi}}{sub {pi}} mass and {pi}{pi} opening angle distributions we find the direct decay into the {sigma} channel to be the dominating decay - at variance with the PDG values, but in favor of the monopole character of the Roper excitation. Since Roper excitation and decay do not result in significant analyzing powers, the reason for the measured large values may be found in small reaction amplitudes, where single {delta} excitation is connected with s-wave pion rescattering - a process not sensed so far experimentally.
DVCS amplitude with kinematical twist-3 terms
Radyushkin, A V
2000-01-01
We compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude we include the operators of twist-3 which appear as total derivatives of twist-2 operators. Our results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. We find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.
Amplitudes, acquisition and imaging
Energy Technology Data Exchange (ETDEWEB)
Bloor, Robert
1998-12-31
Accurate seismic amplitude information is important for the successful evaluation of many prospects and the importance of such amplitude information is increasing with the advent of time lapse seismic techniques. It is now widely accepted that the proper treatment of amplitudes requires seismic imaging in the form of either time or depth migration. A key factor in seismic imaging is the spatial sampling of the data and its relationship to the imaging algorithms. This presentation demonstrates that acquisition caused spatial sampling irregularity can affect the seismic imaging and perturb amplitudes. Equalization helps to balance the amplitudes, and the dealing strategy improves the imaging further when there are azimuth variations. Equalization and dealiasing can also help with the acquisition irregularities caused by shot and receiver dislocation or missing traces. 2 refs., 2 figs.
Duncan, Fraser Andrew
There is considerable interest in the pn to pi^-pp reaction which can proceed by a nonresonant channel from the isospin 0 pn initial state (an NDelta intermediate state cannot be formed). This thesis describes a measurement of analyzing powers and triple differential cross sections for a subset of this reaction, pn to pi^-pp(^1S_0) by isolating the quasifree process in pd to pi^-ppp_{s}. The experimental arrangement selects the relative S-wave component of the outgoing "diproton". The experiment was done on TRIUMF beam line 1B using a LD_2 target; the pion was detected in a magnetic spectrometer, the two outgoing protons in a scintillator bar array. The spectator proton was undetected. Data were taken in August 1989 at 353, 403 and 440 MeV beam energies. Of these the 403 and 440 MeV data are analysed in this thesis and analyzing powers and triple differential cross sections as a function of pion scattering angle extracted at centre of mass kinetic energies, T_{CM}, of 55 and 70 MeV (corresponding to the 403 and 440 MeV beam energies respectively). Partial wave analysis of the data shows that, while the isospin 0 channel dominates the reaction, contributing approximately 75% of the cross section at the energies studied here, there are significant contributions from the s and d-wave pion, isospin 1 channels. Of particular importance is the contribution from the s-wave pion, isospin 1, channel whose interference with the isospin 0 channels produces the characteristic shapes of the cross sections and analyzing powers observed in the data. The d-wave pion, isospin 1 channels, are also required to fully explain the observed analyzing power distributions, and are essential for the T_{CM} = 70MeV data. Comparisons of the pion production data measured in this experiment with pion absorption measurements on ^3He, where the absorption process is pi^-pp(^1S_0) to pn, show a shift in the shape of the differential cross section which can be interpreted as due to differences in
Multi-pion production in deuteron-proton collisions at COSY-ANKE
Energy Technology Data Exchange (ETDEWEB)
Mielke, Malte Marius
2014-07-01
The presented work is a contribution to the research on two- and three pion production in deuteron-proton collisions. Whereas the latter has received very little attention so far, the former is attracting the interest of particle physicists since several decades. An important reason for this is the appearance of the so-called ABC effect, a striking enhancement in the two-pion invariant mass spectrum near its threshold. There is strong evidence that this is related to the presence of nucleons and in the context of recent investigations it is even linked to an excitation of dibaryon resonances. The here presented results from an exclusive measurement of the dp→{sup 3}Heπ{sup +}π{sup -} reaction with the COSY-ANKE facility at an excess energy of 265 MeV benefit from high statistics as well as a good momentum resolution. Events with coincidentally detected {sup 3}Heπ{sup ±} and {sup 3}Heπ{sup +}π{sup -} combinations were used for the analysis. Various selection steps led to a very clean data sample. The limited geometrical acceptance of the ANKE detector was studied in detail in order to successfully elaborate a reliable correction method. Based on this, it was possible to determine differential and double differential cross sections for a large fraction of the backward {sup 3}He hemisphere. The derived invariant mass distributions do allow to illuminate further details of the two-pion production processes. Besides the prominent ABC enhancement, they reveal a significant difference in the behaviour of the positively and negatively charged pions, which is interpreted to be caused by π{sup +}π{sup -} isovector contributions. The total results are successfully described in terms of a N{sup *}(1440)→Δ(1232)→N decay chain. However, the isobar model surprisingly underestimates the charge difference at low two-pion invariant masses, indicating further contribution to the isovector channel. Investigations on the simultaneously measured dp→{sup 3}Heπ{sup +}
Pion scattering to 8/sup -/ stretched states in /sup 60/Ni
Energy Technology Data Exchange (ETDEWEB)
Clausen, B.L.
1988-03-01
Using the Energetic Pion Channel and Spectrometer at the Los Alamos Meson Physics Facility, differential cross sections for pion scattering were measured for ten previously known J/sup ..pi../ = 8/sup /minus// stretched states in /sup 60/Ni. A possible new pure isoscalar stretched state was also found. The data were taken near the /DELTA//sub 3,3/-resonance using 162 MeV incident pions and scattering angles of 65/degree/, 80/degree/, and 90/degree/ for ..pi../sup +/ and 65/degree/ and 80/degree/ for ..pi../sup /minus//. The analysis of the /sup 60/Ni data found that the use of Woods-Saxon wave functions in the theoretical calculations gave much better agreement with data than the use of the usual harmonic oscillator wave functions. The WS theory gave better predictions of: the angle at which the ..pi../sup /minus// and ..pi../sup +/ angular distributions are maximum, the ratios of ..pi../sup /minus// to ..pi../sup +/ cross sections for pure isovector states (which were much larger than unity), and the absolute size of the cross sections for all states (so that the normalization factor necessary to arrive at agreement of theory with data was closer to unity). The theoretical calculations used the distorted wave impulse approximation, including new methods for unbound states. The sensitivities of the calculations to input parameters were investigated. This analysis using WS wave functions was extended to five other nuclei (/sup 12/C, /sup 14/C, /sup 16/O, /sup 28/Si, and /sup 54/Fe) on which both pion scattering and electron scattering have been done. A significant improvement in arriving at a normalization factor close to unity was found when WS wave functions were consistently used for analyzing both pion and electron inelastic scattering data. 101 refs., 26 figs., 13 tabs.
Reconciling threshold and subthreshold expansions for pion-nucleon scattering
Siemens, D; Epelbaum, E; Hoferichter, M; Krebs, H; Kubis, B; Meißner, U -G
2016-01-01
Heavy-baryon chiral perturbation theory (ChPT) at one loop fails in relating the pion-nucleon amplitude in the physical region and for subthreshold kinematics due to loop effects enhanced by large low-energy constants. Studying the chiral convergence of threshold and subthreshold parameters up to fourth order in the small-scale expansion, we address the question to what extent this tension can be mitigated by including the $\\Delta(1232)$ as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the $\\Delta$ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the $\\Delta$-less theory the resummation of $1/m_N$ corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.
Anomalous decays of eta' and eta into four pions
Guo, Feng-Kun; Wirzba, Andreas
2011-01-01
We calculate the branching ratios of the yet unmeasured eta' decays into four pions, based on a combination of chiral perturbation theory and vector-meson dominance. The decays eta' --> 2(pi+ pi-) and eta' --> pi+ pi- 2pi0 are P-wave dominated and can largely be thought to proceed via two rho resonances; we predict branching fractions of (1.0+-0.3)*10^-4 and (2.4+-0.7)*10^-4, respectively, not much lower than the current experimental upper limits. The decays eta' --> 4pi0 and eta --> 4pi0, in contrast, are D-wave driven as long as conservation of CP symmetry is assumed, and are significantly further suppressed; any experimental evidence for the decay eta --> 4pi0 could almost certainly be interpreted as a signal of CP violation. We also calculate the CP-violating amplitudes for eta' --> 4pi0 and eta --> 4pi0 induced by the QCD theta-term.
HBT Pion Interferometry with Phenomenological Mean Field Interaction
Hattori, K.
2010-11-01
To extract information on hadron production dynamics in the ultrarelativistic heavy ion collision, the space-time structure of the hadron source has been measured using Hanbury Brown and Twiss interferometry. We study the distortion of the source images due to the effect of a final state interaction. We describe the interaction, taking place during penetrating through a cloud formed by evaporating particles, in terms of a one-body mean field potential localized in the vicinity of the source region. By adopting the semiclassical method, the modification of the propagation of an emitted particle is examined. In analogy to the optical model applied to nuclear reactions, our phenomenological model has an imaginary part of the potential, which describes the absorption in the cloud. In this work, we focus on the pion interferometry and mean field interaction obtained using a phenomenological pipi forward scattering amplitude in the elastic channels. The p-wave scattering wit h rho meson resonance leads to an attractive mean field interaction, and the presence of the absorptive part is mainly attributed to the formation of this resonance. We also incorporate a simple time dependence of the potential reflecting the dynamics of the evaporating source. Using the obtained potential, we examine how and to what extent the so-called HBT Gaussian radius is varied by the modification of the propagation.
Filin, A A; Epelbaum, E; Hanhart, C; Krebs, H; Kudryavtsev, A E; Myhrer, F
2012-01-01
A complete calculation of the pion-nucleon loops that contribute to the transition operator for $NN\\to NN\\pi$ up-to-and-including next-to-next-to-leading order (N$^2$LO) in chiral effective field theory near threshold is presented. The evaluation is based on the so-called momentum counting scheme, which takes into account the relatively large momentum of the initial nucleons inherent in pion-production reactions. We show that the significant cancellations between the loops found at next-to-leading order (NLO) in the earlier studies are also operative at N$^2$LO. In particular, the $1/m_N$ corrections (with $m_N$ being the nucleon mass) to loop diagrams cancel at N$^2$LO, as do the contributions of the pion loops involving the low-energy constants $c_i$, i=1...4. In contrast to the NLO calculation however, the cancellation of loops at N$^2$LO is incomplete, yielding a non-vanishing contribution to the transition amplitude. Together with the one-pion exchange tree-level operators, the loop contributions provide...
Skorodko, T.(Physikalisches Institut, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 14, Tübingen, 72076, Germany); Bashkanov, M.; H. Clement; Doroshkevich, E.; Khakimova, O.; Kren, F.; Pricking, A.; Wagner, G. J.
2010-01-01
The two-pion production in nucleon-nucleon collisions has been studied by exclusive and kinematically complete experiments from threshold up to $T_p$ = 1.36 GeV at CELSIUS-WASA. At near-threshold energies the total and differential distributions for the $\\pi^+\\pi^-$ and $\\pi^0\\pi^0$ channels are dominated by Roper excitation and its decay into $N\\sigma$ and $\\Delta\\pi$ channels. At beam energies $T_p >$ 1.1 GeV the $\\Delta\\Delta$ excitation governs the two-pion production process. In the $\\pi...
Pion electric polarizability from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Alexandru, Andrei; Lujan, Michael; Freeman, Walter; Lee, Frank [The George Washington University, 725 21st St. NW, Washington DC, 20052 (United States)
2016-01-22
Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New experiments at CERN and Jefferson Lab are planned that will measure the polarizabilities more precisely. Lattice QCD can be used to compute these quantities directly in terms of quark and gluons degrees of freedom, using the background field method. We present results for the electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in polarizability studies.
Pion showers in highly granular calorimeters
Indian Academy of Sciences (India)
Jaroslav Cvach; on behalf of the CALICE Collaboration
2012-10-01
New results on properties of hadron showers created by pion beam at 8–80 GeV in high granular electromagnetic and hadron calorimeters are presented. Data were used for the ﬁrst time to investigate the separation of the neutral and charged hadron showers. The result is important to verify the prediction of the PFA algorithm based up to now on the simulated data only. Next, the properties of hadron showers were compared to different physics lists of GEANT4 version 9.3.
Photoproduction of Neutral Pions off Protons
Crede, V; Wilson, A; Anisovich, A V; Bacelar, J C S; Bantes, R; Bartholomy, O; Bayadilov, D; Beck, R; Beloglazov, Y A; Castelijns, R; Dutz, H; Elsner, D; Ewald, R; Frommberger, F; Funke, Chr; Gregor, R; Gridnev, A; Gutz, E; Hillert, W; Hoffmeister, P; Jaegle, I; Junkersfeld, J; Kalinowsky, H; Kammer, S; Klein, Frank; Klein, Friedrich; Klempt, E; Kotulla, M; Krusche, B; Loehner, H; Lopatin, I V; Lugert, S; Menze, D; Mertens, T; Messchendorp, J G; Metag, V; Nanova, M; Nikonov, V A; Novinski, D; Novotny, R; Ostrick, M; Pant, L M; van Pee, H; Pfeiffer, M; Roy, A; Sarantsev, A V; Schadmand, S; Schmidt, C; Schmieden, H; Schoch, B; Shende, S; Sokhoyan, V; Suele, A; Sumachev, V V; Szczepanek, T; Thoma, U; Trnka, D; Varma, R; Walther, D; Wendel, Ch
2011-01-01
Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction $\\gamma p\\to p\\pi^0$ for photon energies between 0.85 and 2.50 GeV. The $\\pi^0$ mesons are observed in their dominant neutral decay mode: $\\pi^0\\to\\gamma\\gamma$. For the first time, the differential cross sections cover the very forward region, $\\theta_{\\rm c.m.}<60^\\circ$. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances: $G_{17}$(2190), $D_{13}$(2080), and $D_{15}$(2070).
Rare kaon, muon, and pion decay
Energy Technology Data Exchange (ETDEWEB)
Littenberg, L.
1998-12-01
The author discusses the status of and prospects for the study of rare decays of kaons, muons, and pions. Studies of rare kaon decays are entering an interesting new phase wherein they can deliver important short-distance information. It should be possible to construct an alternative unitarity triangle to that determined in the B sector, and thus perform a critical check of the Standard Model by comparing the two. Rare muon decays are beginning to constrain supersymmetric models in a significant way, and future experiments should reach sensitivities which this kind of model must show effects, or become far less appealing.
Threshold Neutral Pion Photoproduction on the Proton
Blin, Astrid Hiller; Ledwig, Tim
2015-01-01
The neutral pion photoproduction on the proton near threshold has a very small scattering cross section when compared to the charged channels, which in ChPT is explained by strong cancellations between the lowest order pieces. Therefore it is very sensitive to higher-order corrections of chiral perturbation theory. We perform a fully covariant calculation up to chiral order p^3 and we investigate the effect of the inclusion of the Delta(1232) resonance as an explicit degree of freedom. We show that the convergence improves, leading to a much better agreement with data at a wide range of energies.
Photoproduction of neutral pions off protons
Crede, V.; Sparks, N.; Wilson, A.; Anisovich, A. V.; Bacelar, J. C. S.; Bantes, R.; Bartholomy, O.; Bayadilov, D.; Beck, R.; Beloglazov, Y. A.; Castelijns, R.; Dutz, H.; Elsner, D.; Ewald, R.; Frommberger, F.; Funke, Chr.; Gregor, R.; Gridnev, A.; Gutz, E.; Hillert, W.; Hoffmeister, P.; Jaegle, I.; Junkersfeld, J.; Kalinowsky, H.; Kammer, S.; Klein, Frank; Klein, Friedrich; Klempt, E.; Kotulla, M.; Krusche, B.; Löhner, H.; Lopatin, I. V.; Lugert, S.; Menze, D.; Mertens, T.; Messchendorp, J. G.; Metag, V.; Nanova, M.; Nikonov, V. A.; Novinski, D.; Novotny, R.; Ostrick, M.; Pant, L. M.; van Pee, H.; Pfeiffer, M.; Roy, A.; Sarantsev, A. V.; Schadmand, S.; Schmidt, C.; Schmieden, H.; Schoch, B.; Shende, S.; Sokhoyan, V.; Süle, A.; Sumachev, V. V.; Szczepanek, T.; Thoma, U.; Trnka, D.; Varma, R.; Walther, D.; Wendel, Ch.
2011-11-01
Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction γp→pπ0 for photon energies between 0.85 and 2.50 GeV. The π0 mesons are observed in their dominant neutral decay mode: π0→γγ. For the first time, the differential cross sections cover the very forward region, θc.m.<60∘. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances G17(2190), D13(2080), and D15(2070).
Quark dynamics and pion-nucleon coupling
Weise, W.; Werner, E.
1981-05-01
In the framework of nonperturbative QCD phenomenology we discuss: (1) The elementary process for the creation of color-singlet qq-pairs inside a hadron. (2) The interaction of the qq-pair with the surrounding quark-gluon medium. An important consequence of these discussions is that meson emission takes place preferentially, if the primary qq-pair is created in the surface region of the hadron. For the case of pseudoscalar coupling we employ PCAC to obtain the coupling of the qq-pair to the pion. The resulting form and coupling strength of the πNN vertex is consistent with the phenomenological OPEP.
Nuclear transparencies from photoinduced pion production
Energy Technology Data Exchange (ETDEWEB)
W. Cosyn; M.C. Martinez; J. Ryckebusch; B. Van Overmeire
2006-12-01
We present a relativistic and cross-section factorized framework for computing nuclear transparencies extracted from A({gamma}, {pi} N) reactions at intermediate energies. The proposed quantum mechanical model adopts a relativistic extension to the multiple-scattering Glauber approximation to account for the final state interactions of the ejected nucleon and pion. The theoretical predictions are compared against the experimental {sup 4}He({gamma},p {pi}{sup -}) data from Jefferson Lab. For those data, our results show no conclusive evidence for the onset of mechanisms related to color transparency.
Single neutral pion production by charged-current $\\bar{\
Aliaga, L; Bercellie, A; Bodek, A; Bravar, A; Brooks, W K; Butkevich, A; Caicedo, D A Martinez; Carneiro, M F; Christy, M E; Chvojka, J; da Motta, H; Devan, J; Dytman, S A; Díaz, G A; Eberly, B; Felix, J; Fields, L; Fine, R; Gago, A M; Gallagher, H; Gran, R; Harris, D A; Higuera, A; Hurtado, K; Kordosky, M; Le, T; Maher, E; Manly, S; Mann, W A; Marshall, C M; McFarland, K S; McGivern, C L; McGowan, A M; Miller, J; Morfín, J G; Mousseau, J; Nelson, J K; Norrick, A; Osta, J; Palomino, J L; Paolone, V; Park, J; Patrick, C E; Perdue, G N; Rakotondravohitra, L; Ramirez, M A; Ransome, R D; Ray, H; Ren, L; Rodrigues, P A; Ruterbories, D; Schellman, H; Schmitz, D W; Sobczyk, J T; Salinas, C J Solano; Tagg, N; Tice, B G; Valencia, E; Walton, T; Wolcott, J; Yepes-Ramirez, H; Zavala, G; Zhang, D; Ziemer, B P
2015-01-01
Single neutral pion production via muon antineutrino charged-current interactions in plastic scintillator (CH) is studied using the \\minerva detector exposed to the NuMI low-energy, wideband antineutrino beam at Fermilab. Measurement of this process constrains models of neutral pion production in nuclei, which is important because the neutral-current analog is a background for $\\bar{\
Limits on Lorentz violation from charged-pion decay
P. Noordmans, J.; K. Vos, K.
2014-01-01
Charged-pion decay offers many opportunities to study Lorentz violation. Using an effective field theory approach, we study Lorentz violation in the lepton, W-boson, and quark sectors and derive the differential pion-decay rate, including muon polarization. Using coordinate redefinitions we are able
Optimization of Experiment Detecting Kaon and Pion Internal Structure
Wacht, Jacob
2016-09-01
Pions and kaons are the lightest two-quark systems in Nature. Scientists believe that the rules governing the strong interaction are chirally, symmetric. If this were true, the pion would have no mass. The chiral symmetry is broken dynamically by quark-gluon interactions, giving the pion mass. The pion is thus seen as the key to confirm the mechanism that dynamically generates nearly all of the mass of hadrons and central to the effort to understand hadron structure. The most prominent observables are the meson form factors. Experiments are planned at the 12 GeV Jefferson Lab. An experiment aimed at shedding light on the kaon's internal structure is scheduled to run in 2017. The experimental setup has been optimized for detecting kaons, but it may allow for detecting pions between values of Q2 of 0.4 and 5.5 GeV2. Measurements of the separated pion cross section and exploratory extraction of the pion form factor from electroproduction at low Q2 could be compared to earlier e-pi scattering data, and thus help validating the method. At high Q2, these measurements provide the first L/T separated cross sections and could help guide planned dedicated pion experiments. I will present possible parasitic studies with the upcoming kaon experiment. This work was supported in part by NSF Grant PHY-1306227.
Further comment on pion electroproduction and the axial form factor
Bernard, V; Meißner, Ulf G; Mei{\\ss}ner, Ulf-G.
2001-01-01
We show that a recent claim (H.Haberzettl, Phys. Rev. Lett. 85 (2000) 3576) that one cannot extract the nucleon weak axial form factor G_A (t) from charged pion threshold electroproduction is incorrect. Thus previous calculations remain valid and threshold charged pion electroproduction experiments can indeed be used to determine G_A (t), and they should certainly be pursued.
Real topological string amplitudes
Narain, K. S.; Piazzalunga, N.; Tanzini, A.
2017-03-01
We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.
Comparative Energy Dependence of Proton and Pion Degradation in Diamond
Lazanu, Ionel
1999-01-01
A comparative theoretical study of the damages produced by protons and pions, in the energy range 50 MeV - 50 GeV, in diamond, is presented. The concentration of primary defects (CPD) induced by hadron irradiation is used to describe material degradation. The CPD has very different behaviours for protons and pions: the proton degradation is important at low energies and is higher than the pion one in the whole energy range investigated, with the exception of the Delta33 resonance region, where a large maximum of the degradation exists for pions. In comparison with silicon, the most investigated and the most studied material for detectors, diamond theoretically proves to be one order of magnitude more resistant, both to proton and pion irradiation.
Subthreshold production of pions in coincidence with light particles
Energy Technology Data Exchange (ETDEWEB)
Barbera, R.; Badala, A.; Adorno, A.; Bonasera, A.; Di Toro, M.; Palmeri, A.; Pappalardo, G.S.; Riggi, F.; Russo, G. (Istituto Nazionale di Fisica Nucleare, Catania (Italy)); Bizard, G.; Durand, D.; Laville, J.L. (Caen Univ., 14 (France). Lab. de Physique Corpusculaire); Jin, G.M. (Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France)); Rosato, E. (Naples Univ. (Italy). Dipt. di Scienze Fisiche Istituto Nazionale di Fisica Nucleare, Naples (Italy))
1990-12-03
He ions have been detected in coincidence with charged pions in the reaction {sup 16}O on {sup 27}Al at E{sub lab}=94 MeV/u. We analyse velocity spectra and cross-sections of He ions emitted in the angular range 4deg/150deg in coincidence with charged pions detected at 90deg. A two source emission mechanism of the helium particles and a pion statistical production from an equilibrated participant zone is stressed. The absolute yields at different angles are compared with results of a theoretical model for medium energy heavy ion reactions in the frame of a participant-spectator picture. A comparison of the pion energy spectra with Boltzmann-Nordheim-Vlasov calculations and a discussion on the time scale for pion emission is also presented. (orig.).
Regge approach to charged-pion photoproduction at invariant energies above 2 GeV
Energy Technology Data Exchange (ETDEWEB)
Sibirtsev, A; Haidenbauer, J; Krewald, S; Lee, T S.H.; Meissner, U -G; Thomas, A W
2007-10-01
A Regge model with absorptive corrections is employed in a global analysis of the world data on positive and negative pion photoproduction for photon energies from 3 to 8~GeV. In this region resonance contributions are expected to be negligible so that the available experimental information on differential cross sections and single polarization observables at $-t{\\leq}2$ GeV$^2$ allows us to determine the non-resonant part of the reaction amplitude reliably. The model amplitude is then used to predict observables for photon energies below $3$ GeV. Differences between our predictions and data in this energy region are systematically examined as possible signals for the presence of excited baryons. We find that the data available for the polarized photon asymmetry show promising resonance signatures at invariant energies around 2~GeV. With regard to differential cross sections the analysis of negative pion photoproduction data, obtained recently at JLab, indicates likewise the presence of resonance structures around 2~GeV.
Precision determination of the pion-nucleon $\\sigma$-term from Roy-Steiner equations
Hoferichter, Martin; Kubis, Bastian; Meißner, Ulf-G
2015-01-01
We present a determination of the pion-nucleon ($\\pi N$) $\\sigma$-term $\\sigma_{\\pi N}$ based on the Cheng-Dashen low-energy theorem (LET), taking advantage of the recent precision data from pionic atoms to pin down the threshold $\\pi N$ amplitude as well as of constraints from analyticity, unitarity, and crossing symmetry in the form of Roy-Steiner equations to perform the extrapolation to the Cheng-Dashen point in a reliable manner. With isospin-violating corrections included both in the scattering lengths and the LET, we obtain $\\sigma_{\\pi N}=(59.1\\pm 1.9\\pm 3.0)$ MeV $=(59.1\\pm 3.5)$ MeV, where the first error refers to uncertainties in the $\\pi N$ amplitude and the second to the LET. Consequences for the scalar nucleon couplings relevant for the direct detection of dark matter are discussed.
High resolution study of the inclusive production of massive muon pairs by intense pion beams
2002-01-01
This experiment measures with high resolution and large acceptance the inclusive production of massive muon pairs with the intense pion beam (up to $10^{10} \\pi/$pulse) in the experimental hall ECN3. The experiment explores extended M$^{2}$/s, x and transverse momentum ranges. The study of the departures of the lepton-pair production cross- section from scaling constitutes a good test of QCD ideas; in the framework of the 'Drell-Yan' process, the experiment allows a detailed study of the pion parton distribution functions. The detector consists of a beam dump, a pulsed toroidal a magnet, MWPC's and scintillator hodoscopes. Its $\\sim 2$% mass resolution at 10 GeV is adequate for the substraction of resonances in the high-mass region.
Study of the pion trajectory in the photoproduction of leading neutrons at HERA
Chekanov, S; Abt, I; Adamczyk, L; Adamus, M; Adler, V; Aghuzumtsyan, G; Antonioli, P; Antonov, A; Arneodo, M; Bailey, D S; Bamberger, A; Barakbaev, A N; Barbagli, G; Barbi, M; Bari, G; Barreiro, F; Bartsch, D; Basile, M; Behrens, U; Bellagamba, L; Bellan, P M; Benen, A; Bertolin, A; Bhadra, S; Bloch, I; Bold, T; Boos, E G; Borras, K; Boscherini, D; Brock, I; Brook, N H; Brugnera, R; Brümmer, N; Bruni, A; Bruni, G; Bussey, P J; Butterworth, J M; Büttner, C; Bylsma, B; Caldwell, A; Capua, M; Cara Romeo, G; Carli, T; Carlin, R; Catterall, C D; Chiochia, V; Chwastowski, J; Ciborowski, J; Ciesielski, R; Cifarelli, Luisa; Cindolo, F; Cloth, P; Cole, J E; Collins-Tooth, C; Contin, A; Cooper-Sarkar, A M; Coppola, N; Cormack, C; Corradi, M; Corriveau, F; Costa, M; Cottrell, A; D'Agostini, Giulio; Dal Corso, F; Danilov, P; Dannheim, D; De Pasquale, S; Dementiev, R K; Derrick, M; Devenish, R C E; Dhawan, S; Dobur, D; Dolgoshein, B A; Doyle, A T; Drews, G; Durkin, L S; Dusini, S; Eisenberg, Y; Ermolov, P F; Eskreys, Andrzej; Everett, A; Ferrando, J; Ferrero, M I; Figiel, J; Filges, D; Foster, B; Foudas, C; Fourletov, S; Fourletova, J; Fricke, U; Fusayasu, T; Gabareen, A; Galas, A; Gallo, E; Garfagnini, A; Geiser, A; Genta, C; Gialas, I; Giusti, P; Gladilin, L K; Gladkov, D; Glasman, C; Gliga, S; Goers, S; Goncalo, R; González, O; Gosau, T; Göttlicher, P; Grabowska-Bold, I; Grigorescu, G; Grijpink, S; Grzelak, G; Gutsche, O; Gwenlan, C; Haas, T; Hain, W; Hall-Wilton, R; Hamatsu, R; Hamilton, J; Hanlon, S; Hart, J C; Hartmann, H; Hartner, G; Heaphy, E A; Heath, G P; Helbich, M; Heusch, C A; Hilger, E; Hillert, S; Hirose, T; Hochman, D; Holm, U; Horn, C; Iacobucci, G; Iga, Y; Inuzuka, M; Irrgang, P; Jakob, H P; Jones, T W; Kagawa, S; Kahle, B; Kaji, H; Kananov, S; Karshon, M; Karstens, F; Kataoka, M; Katkov, I I; Kcira, D; Keramidas, A; Khein, L A; Kim, J Y; Kind, O; Kisielewska, D; Kitamura, S; Koffeman, E; Kohno, T; Kooijman, P; Koop, T; Korzhavina, I A; Kotanski, A; Kötz, U; Kowal, A M; Kowal, M; Kowalski, H; Kramberger, G; Kreisel, A; Krumnack, N; Kuze, M; Kuzmin, V A; Labarga, L; Labes, H; Lainesse, J; Lammers, S; Lelas, D; Levchenko, B B; Levy, A; Li, L; Lightwood, M S; Lim, H; Lim, I T; Limentani, S; Ling, T Y; Liu, X; Löhr, B; Lohrmann, E; Loizides, J H; Long, K R; Longhin, A; Lukina, O Yu; Luzniak, P; Ma, K J; Maddox, E; Magill, S; Mankel, R; Margotti, A; Marini, G; Martin, J F; Mastroberardino, A; Matsuzawa, K; Mattingly, M C K; McCubbin, N A; Melzer-Pellmann, I A; Menary, S R; Metlica, F; Meyer, U; Miglioranzi, S; Milite, M; Mirea, A; Monaco, V; Montanari, A; Musgrave, B; Nagano, K; Namsoo, T; Nania, R; Nguyen, C N; Nigro, A; Ning, Y; Notz, D; Nowak, R J; Nuncio, A E; Oh, B Y; Olkiewicz, K; Pac, M Y; Padhi, S; Palmonari, F; Parenti, A; Park, I H; Patel, S; Paul, E; Pavel, Usan; Pawlak, J M; Pelfer, P G; Pellegrino, A; Pesci, A; Piotrzkowski, K; Plucinsky, P P; Pokrovskiy, N S; Polini, A; Posocco, M; Proskuryakov, A S; Przybycien, M B; Rautenberg, J; Raval, A; Reeder, D D; Ren, Z; Renner, R; Repond, J; Rinaldi, L; Riveline, U; Robins, S; Rosin, M; Ruspa, M; Ryan, P; Sacchi, R; Salehi, H; Sartorelli, G; Savin, A A; Saxon, D H; Schagen, S; Schioppa, M; Schlenstedt, S; Schleper, P; Schmidke, W B; Schneekloth, U; Schörner-Sadenius, T; Sciulli, F; Shcheglova, L M; Skillicorn, I O; Slominski, W; Smith, W H; Soares, M; Solano, A; Son, D; Sosnovtsev, V V; Stairs, D G; Stanco, L; Standage, J; Stifutkin, A; Stonjek, S; Stopa, P; Stösslein, U; Straub, P B; Suchkov, S; Susinno, G; Suszycki, L; Sutiak, J; Sutton, M R; Sztuk, J; Szuba, D; Szuba, J; Tandler, J; Tapper, A D; Targett-Adams, C; Tassi, E; Tawara, T; Terron, J; Tiecke, H G; Tokushuku, K; Tsurugai, T; Turcato, M; Tymieniecka, T; Ukleja, A; Ukleja, J; Vázquez, M; Vlasov, N N; Voss, K C; Walczak, R; Walsh, R; Wang, M; Whitmore, J J; Wichmann, K; Wick, K; Wiggers, L; Wills, H H; Wing, M; Wolf, G; Yamada, S; Yamashita, T; Yamazaki, Y; Yoshida, R; Youngman, C; Zambrana, M; Zawiejski, L; Zeuner, W; Zhautykov, B O; Zichichi, A; Ziegler, A; Zotkin, S A; De Favereau, J; De Wolf, E; Del Peso, J
2004-01-01
Energetic neutrons produced in ep collisions at HERA have been studied with the ZEUS detector in the photoproduction regime at a mean photon-proton center-of-mass energy of 220 GeV. The neutrons carry a large fraction 0.6 < x_L < 0.925 of the incoming proton energy and the four-momentum-transfer squared at the proton-neutron vertex is small, |t| < 0.425 GeV^2. The x_L distribution of the neutrons is measured in bins of t. The (1-x_L) distributions in the bins of t studied satisfy a power law dN/dx_L ~ (1-x_L)^a(t), with the powers a(t) following a linear function of t: a(t) = 1.08 +/- 0.08(stat.) +0.15/-0.28(syst.) - [2.78 +/- 0.32(stat.) +0.51/-0.47(syst.) GeV^-2]t. This result is consistent with the expectations of pion-exchange models, in which the incoming proton fluctuates to a neutron-pion state and the electron interacts with the pion.
Protostring scattering amplitudes
Thorn, Charles B.
2016-11-01
We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.
Rafatian, Ali
Fermilab E769, a high statistics charm hadroproduction experiment, collected approximately 370 times 10^6 events during the fixed target run period of 1987-88. Using the Tagged Photon Spectrometer, the experiment was performed with a 250 GeV beam of mixed hadrons (pi^{+/- }, K^{+/-}, p) interacting with a segmented foil target of Be, Al, Cu, and W. The use of different beam particle types and polarities allowed E769 to explore the flavor dependence of charm hadroproduction while the choice of different target materials afforded the experiment a measurement of the atomic mass dependence. Using samples of 388 +/- 31 D^0/overline{D ^0} and 127 +/- 14 D^{*+/-}(pi ^{+/-}D^0/overline{D ^0}) events produced from pi ^{+/-} beam interactions, the shape parameters of the differential cross section distributions in fractional longitudinal momentum (x _{F}) and in transverse momentum (P_{rm t}) were determined. The final state of D^0 in both samples is the hadronic 4-prong (K^ -pi^+pi^-pi^+) decay mode. Fitting dsigma/dx_{F } distributions to the functional form (1 - x_{F})^{n} yields values of n = 4.2 +/- 0.5 for D^0/overline{D^0} , and n = 2.5 +/- 0.7 for D^{*+/-}. For dsigma/dP_sp{t}{2} distributions, the fit to the functional form exp( -bP_sp{t}{2}) gives values of b = 1.00 +/- 0.09 (GeV/c)^{-2} for D ^0/overline{D^0}, and b = 0.62 +/- 0.10 (GeV/c) ^{-2} for D^{ *+/-}. The difference in n values for the non-leading versus the leading samples of D ^* production are measured to be 1.7 +/- 1.4, indicative a weak leading particle effect. Finally, the asymmetry for leading versus non-leading D^*'s was determined to be 0.20 +/- 0.14.
Protostring Scattering Amplitudes
Thorn, Charles B
2016-01-01
We calculate some tree level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a lightcone worldsheet which supports $s$ integer moded Grassmann fields. In the generalization we supplement this Grassmann worldsheet system with $d=24-s$ transverse coordinate worldsheet fields. The protostring corresponds to $s=24$ and the bosonic string to $s=0$. The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that $s$ is even we calculate the multi-string scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of $s/2$ compactified and $d$ uncompactified bosonic worldsheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then ...
$K^+$-nucleus potentials from $K^+$-nucleon amplitudes
Friedman, E
2016-01-01
Optical potentials for $K^+$-nucleus interactions are constructed from $K^+$-nucleon amplitudes using recently developed algorithm based on $K^+$-N kinematics in the nuclear medium. With the deep penetration of $K^+$ mesons into the nucleus at momenta below 800~MeV/c it is possible to test this approach with greater sensitivity than hitherto done with $K^-$ and pions. The energy-dependence of experimental reaction and total cross sections on nuclei is better reproduced with this approach compared to fixed-energy amplitudes. The inclusion of Pauli correlations in the medium also improves the agreement between calculation and experiment. The absolute scale of the cross sections is reproduced very well for $^6$Li but for C, Si and Ca calculated cross sections are (23$\\pm4$)\\% smaller than experiment, in agreement with earlier analyses. Two phenomenological models that produce such missing strength suggest that the imaginary part of the potential needs about 40\\% enhancement.
K+-nucleus potentials from K+-nucleon amplitudes
Friedman, E.
2016-10-01
Optical potentials for K+-nucleus interactions are constructed from K+-nucleon amplitudes using recently developed algorithm based on K+-N kinematics in the nuclear medium. With the deep penetration of K+ mesons into the nucleus at momenta below 800 MeV / c it is possible to test this approach with greater sensitivity than hitherto done with K- and pions. The energy-dependence of experimental reaction and total cross sections on nuclei is better reproduced with this approach compared to fixed-energy amplitudes. The inclusion of Pauli correlations in the medium also improves the agreement between calculation and experiment. The absolute scale of the cross sections is reproduced very well for 6Li but for C, Si and Ca calculated cross sections are (23 ± 4)% smaller than experiment, in agreement with earlier analyses. Two phenomenological models that produce such missing strength suggest that the imaginary part of the potential needs about 40% enhancement.
Dilepton bremsstrahlung from pion-pion scattering in a relativistic OBE model
Eggers, H C; Gale, C; Haglin, K L
1996-01-01
We have made a detailed and quantitative study of dilepton production via bremsstrahlung of a virtual photon during pion-pion collisions. Most calculations of electromagnetic radiation from strong interaction processes rely on the soft photon approximation (SPA). The conditions underlying this approximation are generally violated when dilepton spectra are calculated in terms of their invariant mass, so that an approach going beyond the SPA becomes necessary. Superseding previous derivations, we derive an exact formula for the bremsstrahlung cross section. The resulting formulation is compared to various forms based on the SPA, the two-particle phase space approximation and R\\"uckl's formula using a relativistic One Boson Exchange (OBE) model. Within the OBE approach, we show that approximations to the bremsstrahlung dilepton cross sections often differ greatly from the exact result; discrepancies become greater both with rising temperature and with invariant mass. Integrated dilepton production rates are over...
Development of the pion tracker for HADES spectrometer
Energy Technology Data Exchange (ETDEWEB)
Lalik, Rafal [Excellence Cluster ' ' Universe' ' , TU Muenchen, Boltzmannstr.2, 85748 Garching (Germany); Collaboration: HADES-Collaboration
2014-07-01
The beam detector for experiments with pion beams at the HADES spectrometer in GSI Darmstadt has been developed. The main goal of this development is to provide efficient event by event reconstruction of secondary pion momenta. Pions are created impacting nitrogen or proton beams on a secondary beryllium target and are then delivered through a chicane to the experimental areas. The expected momentum spread of the secondary pion beam is about 8% whereas simulated resolution of reconstructed momenta is below 0.5%. The challenging issue is to achieve an accurate measurement (on order of per-mile) of each pion in a high intensity (10{sup 8} part./spill) environment along the pion-bean chicane. This translates into a rate of 10{sup 6} pion/spill with a kinetic energy of 1-2 GeV at the HADES target point. The tracking system is based on double-sided silicon strips sensors build in radiation hardness technology, and a n-XYTER ASIC front-end readout. The trigger logic is implemented in the TRB3 boards. The whole system is designed as a standalone, easy scalable and portable. In this talk we are showing status and performance of the system, and recent results obtained in the laboratory and with proton beams at COSY with 2 GeV protons.
Development of the pion tracker for HADES spectrometer
Energy Technology Data Exchange (ETDEWEB)
Lalik, Rafal [Technische Univ. Muenchen, Garching (Germany). Excellence Cluster Universe; Collaboration: HADES-Collaboration
2013-07-01
We are working on the development of the beam detector for experiments with pion beams at HADES spectrometer in GSI Darmstadt. Pions are created impacting nitrogen or proton beams on a secondary beryllium target and are then delivered through a chicane to the experimental areas. The expected momentum spread of the secondary pion beam is about 8 % and the main goal of this beam detector is to deliver information about the pion momentum for each beam particle. The challenging issue is to achieve an accurate measurement (∼ % fj) of each pion in a high intensity (10{sup 8} part./spill) environment along the pion-bean chicane. This translates into a rate of 10{sup 6} pion/spill with a kinetic energy of 1-2 GeV at the HADES target point. We are currently testing a tracker system, based on double-sided silicon strips detectors with higher radiation hardness and n-XYTER ASIC readout. For prototyping we have prepared the acquisition system compatible with the CBM data acquisition system, for the future employment with HADES we are currently working on acquisition based on the novel TRB3 board. In this talk we are showing current status and performance of the system, and recent results obtained in the laboratory and with proton beams.
Nucleon and pion structure with lattice QCD simulations at physical value of the pion mass
Abdel-Rehim, A; Constantinou, M; Dimopoulos, P; Frezzotti, R; Hadjiyiannakou, K; Jansen, K; Kallidonis, Ch; Kostrzewa, B; Koutsou, G; Mangin-Brinet, M; Oehm, M; Rossi, G C; Urbach, C; Wenger, U
2015-01-01
We present results on the nucleon scalar, axial and tensor charges as well as on the momentum fraction, and the helicity and transversity moments. The pion momentum fraction is also presented. The computation of these key observables is carried out using lattice QCD simulations at a physical value of the pion mass. The evaluation is based on gauge configurations generated with two degenerate sea quarks of twisted mass fermions with a clover term. We investigate excited states contributions with the nucleon quantum numbers by analyzing three sink-source time separations. We find that, for the scalar charge, excited states contribute significantly and to a less degree to the nucleon momentum fraction and helicity moment. Our analysis yields a value for the nucleon axial charge agrees with the experimental value and we predict a value of 1.027(62) in the $\\overline{\\text{MS}}$ scheme at 2 GeV for the isovector nucleon tensor charge directly at the physical point. The pion momentum fraction is found to be $\\langl...
Institute of Scientific and Technical Information of China (English)
乔大勇; 杨璇; 夏长锋; 曾琪; 潘春晖; 练彬
2014-01-01
In order to increase the deflection, the effect of comb structure on the twisting amplitude for two-dimensional(2D)microscanner is researched on basis of the nonlinear dynamics theory in this paper,and it can be obtained that the effect of the divergent distribution is superior to parallel distribution. Besides, the samples are fabricated based on silicon-on-insulator(SOI)technology,and then the electromechanical characteristic is tested. The test results demonstrate the microscanner with divergent comb distribution has greater twisting amplitude,which agrees with the theoretical analysis. The microscanner with divergent distribution could generate maximum twisting angles of 12. 3° and 13. 49° under the square wave of 42 V, while the sample with parallel distribution could generate maximum twisting angles of 10. 25° and 11. 68° under the same square wave.%为增大静电驱动二维微扫描镜的机械转角，基于非线性动力学理论研究了不同梳齿结构对其振幅的影响，理论上得到发散型梳齿分布相较于平行型梳齿分布具有更大的机械转角。此外，采用绝缘体上硅( SOI)加工工艺设计并制作了这两种结构的微扫描镜，并对其相关特性进行了测试。测试结果表明：在相同的驱动电压下，发散型结构始终都比平行型结构具有更大的机械转角，与仿真结果基本一致；当加载驱动电压为42 V的方波信号时，发散型结构扫描镜的可动框架和镜面的最大机械转角可以达到12.3°、13.49°，而平行型结构扫描镜的可动框架和镜面的最大机械转角则为10.25°、11.68°。
Neutrinos from PIon Beam Line, nuPIL
Energy Technology Data Exchange (ETDEWEB)
Lagrange, J. B. [Imperial Coll., London; Pasternak, J. [Imperial Coll., London; Bross, A. [Fermilab; Liu, A. [Fermilab
2016-05-05
LBNF-DUNE (Long Baseline Neutrino Facilities - Deep Underground Neutrino Experiment) is a project based at Fermilab to study neutrino oscillations. The current baseline regarding the neutrino production considers the conventional approach: a high energy proton beam hits a target, producing pions that are collected by a horn and that decay in a decay pipe. An alternative solution, called nuPIL (neutrinos from a Pion beam Line) consists of using a beam line to guide the pions to clean the beam and to put instrumentation to monitor it. This paper presents the concept and the first preliminary results.
Remarks on the pion-nucleon sigma-term
Hoferichter, Martin; Kubis, Bastian; Meißner, Ulf-G
2016-01-01
The pion-nucleon $\\sigma$-term can be stringently constrained by the combination of analyticity, unitarity, and crossing symmetry with phenomenological information on the pion-nucleon scattering lengths. Recently, lattice calculations at the physical point have been reported that find lower values by about $3\\sigma$ with respect to the phenomenological determination. We point out that a lattice measurement of the pion-nucleon scattering lengths could help resolve the situation by testing the values extracted from spectroscopy measurements in pionic atoms.
Thermal and Nonthermal Pion Enhancements with Chiral Symmetry Restoration
Zhuang, P
2001-01-01
The pion production by sigma decay and its relation with chiral symmetry restoration in a hot and dense matter are investigated in the framework of the Nambu-Jona-Lasinio model. The decay rate for the process sigma -> 2pion to the lowest order in a 1/N_c expansion is calculated as a function of temperature T and chemical potential mu. The thermal and nonthermal enhancements of pions generated by the decay before and after the freeze-out present only in the crossover region of the chiral symmetry transition. The strongest nonthermal enhancement is located in the vicinity of the endpoint of the first-order transition.
Pion Effect of Nuclear Matter in a Chiral Sigma Model
Institute of Scientific and Technical Information of China (English)
HU Jin-niu; Y.Ogawa; H.Toki; A.Hosaka; SHEN Hong
2009-01-01
We develop a new framework for the study of the nuclear matter based on the linear sigma model.We introduce a completely new viewpoint on the treatment of the nuclear matter with the inclusion of the pion.We extend the relativistic chiral mean field model by using the similar method in the tensor optimized shell model.We also regulate the pion-nucleon interaction by considering the form-factor and short range repulsion effects.We obtain the equation of state of nuclear matter and study the importance of the pion effect.
Azimuthal Dependence of Pion Interferometry at the AGS
Lisa, M A; Alexander, J M; Anderson, M; Best, D; Brady, F P; Case, T; Caskey, W; Cebra, D; Chance, J L; Chung, P; Cole, B; Crowe, K M; Das, A C; Draper, J E; Gilkes, M L; Gushue, S; Heffner, M; Hirsch, A S; Hjort, E L; Huo, L; Justice, M; Kaplan, M; Keane, D; Kintner, J C; Klay, J L; Krofcheck, D; Lacey, R A; Lauret, J; Liu, H; Liu, Y M; McGrath, R; Milosevich, Z; Odyniec, Grazyna Janina; Olson, D L; Panitkin, S Y; Pinkenburg, C H; Porile, N T; Rai, G; Ritter, H G; Romero, J L; Scharenberg, R P; Schröder, L; Srivastava, B; Stone, N T B; Symons, T J M; Wells, R; Whitfield, J; Wienold, T; Witt, R; Wood, L; Zhang Wei Ning
2000-01-01
Two-pion correlation functions, measured as a function of azimuthal emission angle with respect to the reaction plane, provide novel information on the anisotropic shape and orientation of the pion-emitting zone formed in heavy ion collisions. We present the first experimental determination of this information, for semi-central Au+Au collisions at 2-6 AGeV. The source extension perpendicular to the reaction plane is greater than the extension in the plane, and tilt of the pion source in coordinate space is found to be opposite its tilt in momentum space.
Taylor, Tomasz R.
2017-05-01
This a pedagogical introduction to scattering amplitudes in gauge theories. It proceeds from Dirac equation and Weyl fermions to the two pivot points of current developments: the recursion relations of Britto, Cachazo, Feng and Witten, and the unitarity cut method pioneered by Bern, Dixon, Dunbar and Kosower. In ten lectures, it covers the basic elements of on-shell methods.
Target tracking based on frequency spectrum amplitude
Institute of Scientific and Technical Information of China (English)
Guo Huidong; Zhang Xinhua; Xia Zhijun
2006-01-01
The amplitude of frequency spectrum can be integrated with probabilistic data association (PDA) to distinguish the target with clutter echoes, especially in low SNR underwater environment. A new target-tracking algorithm is presented which adopts the amplitude of frequency spectrum to improve target tracking in clutter. The probabilistic density distribution of frequency spectrum amplitude is analyzed. By simulation, the results show that the algorithm is superior to PDA. This approach enhances stability for the association probability and increases the performance of target tracking.
Pions near the chiral critical point
Hippert, M.; Fraga, E. S.; Santos, E. M.
2016-04-01
It is an exciting possibility that the QCD critical point can be found in ultrarelativistic heavy-ion collision experiments (HICs). While quantities such as some event-by-event moments of specific observables should display strong non-monotonic behavior near the critical point and could, hence, be used as signatures of criticality, it is not clear that this behavior could effectively be observed in the highly non-ideal scenario of HICs. We here employ Monte Carlo simulations to test second-order moments of pion observables as possible signatures of the critical point while taking into account some realistic ingredients, similar to the ones found in HICs. We make use of simplified models to introduce spurious contributions and dynamical effects.
Incoherent neutral pion photoproduction on 12C.
Tarbert, C M; Watts, D P; Aguar, P; Ahrens, J; Annand, J R M; Arends, H J; Beck, R; Bekrenev, V; Boillat, B; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R; Downie, E J; Föhl, K; Glazier, D I; Grabmayr, P; Gregor, R; Heid, E; Hornidge, D; Jahn, O; Kashevarov, V L; Knezevic, A; Kondratiev, R; Korolija, M; Kotulla, M; Krambrich, D; Krusche, B; Lang, M; Lisin, V; Livingston, K; Lugert, S; Macgregor, I J D; Manley, D M; Martinez, M; McGeorge, J C; Mekterovic, D; Metag, V; Nefkens, B M K; Nikolaev, A; Novotny, R; Owens, R O; Pedroni, P; Polonski, A; Prakhov, S N; Price, J W; Rosner, G; Rost, M; Rostomyan, T; Schadmand, S; Schumann, S; Sober, D; Starostin, A; Supek, I; Thomas, A; Unverzagt, M; Walcher, Th; Zehr, F
2008-04-04
We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The 12C(gamma,pi(0))(12)C*(4.4 MeV) reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a pi(0) spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. Such data are sensitive to the propagation of the Delta in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a Delta-hole model.
Charged pion production in C+C and Ar+KCl collisions measured with HADES
Tlustý, P; Balanda, A; Bellia, G; Belver, D; Belyaev, A; Blanco, A; Boehmer, M; Boyard, J L; Braun-Munzinger, P; Cabanelas, P; Castro, E; Chernenko, S; Christ, T; Destefanis, M; Díaz, J; Dohrmann, F; Dybczak, A; Fabbietti, L; Fateev, O; Finocchiaro, P; Fonte, P; Friese, J; Fröhlich, I; Galatyuk, T; Garzón, J A; Gernhäuser, R; Gil, A; Gilardi, C; Golubeva, M; Gonzalez-Diaz, D; Grosse, E; Guber, F; Heilmann, M; Hennino, T; Holzmann, R; Ierusalimov, A; Iori, I; Ivashkin, A; Jurkovic, M; Kämpfer, B; Kanaki, K; Karavicheva, T; Kirschner, D; König, I; König, W; Kolb, B W; Kotte, R; Kozuch, A; Krasa, A; Krizek, F; Krücken, R; Kühn, W; Kugler, A; Kurepin, A; Lamas-Valverde, J; Lang, S; Lange, J S; Lapidus, K; Liu, T; Lopes, L; Lorenz, M; Maier, L; Mangiarotti, A; Marin, J; Markert, J; Metag, V; Michalska, B; Michel, J; Mishra, D; Moriniere, E; Mousa, J; Müntz, C; Naumann, L; Novotny, R; Otwinowski, J; Pachmayer, Y C; Palka, M; Parpottas, Y; Pechenov, V; Pechenova, O; Cavalcanti, T Perez; Pietraszko, J; Przygoda, W; Ramstein, B; Reshetin, A; Rustamov, A; Sadovskii, A; Salabura, P; Schmah, A; Simon, R; Sobolev, Yu G; Spataro, S; Spruck, B; Ströbele, H; Stroth, J; Sturm, C; Sudol, M; Tarantola, A; Teilab, K; Traxler, M; Trebacz, R; Tsertos, H; Veretenkin, I; Wagner, V; Weber, M; Wisniowski, M; Wüstenfeld, J; Yurevich, S; Zanevsky, Y; Zhou, P; Zumbruch, P
2009-01-01
Results of a study of charged pion production in 12C+12C collisions at incident beam energies of 1A GeV and 2A GeV, and 40Ar+natKCl at 1.76AGeV, using the spectrometer HADES at GSI, are presented. We have performed a measurement of the transverse momentum distributions of pi+- mesons covering a fairly large rapidity interval, in case of the C+C collision system for the first time. The yields, transverse mass and angular distributions are compared with a transport model as well as with existing data from other experiments.
Single-pion production in pp collisions at 0.95 GeV/c (II)
Energy Technology Data Exchange (ETDEWEB)
Abd El-Samad, S. [Atomic Energy Authority NRC Cairo, Cairo (Egypt); Bilger, R.; Clement, H.; Dietrich, M.; Doroshkevich, E.; Ehrhardt, K.; Erhardt, A.; Kress, J.; Meier, R.; Wagner, G.J.; Weidlich, U.; Zhang, G. [Physikalisches Institut der Universitaet Tuebingen, Tuebingen (Germany); Brinkmann, K.T.; Freiesleben, H.; Jaekel, R.; Jakob, B.; Karsch, L.; Kuhlmann, E.; Schulte-Wissermann, M.; Sun, G.Y. [Technische Universitaet Dresden, Dresden (Germany); Dshemuchadse, S. [Technische Universitaet Dresden, Dresden (Germany); Forschungszentrum Rossendorf, Dresden (Germany); Eyrich, W.; Hauffe, J.; Schroeder, W.; Stinzing, F.; Waechter, J.; Wagner, M.; Wirth, S. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen-Nuernberg (Germany); Filippi, A.; Marcello, S. [University of Torino (Italy); INFN, Sezione di Torino, Torino (Italy); Fritsch, M. [Ruhr-Universitaet Bochum, Bochum (Germany); Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen-Nuernberg (Germany); Geyer, R.; Gillitzer, A.; Hesselbarth, D.; Kilian, K.; Marwinski, S.; Morsch, H.P.; Ritman, J.; Roderburg, E. [Forschungszentrum Juelich, Juelich (Germany); Moeller, K.; Naumann, L. [Forschungszentrum Rossendorf, Dresden (Germany); Schoenmeier, P. [Technische Universitaet Dresden, Dresden (Germany); Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen-Nuernberg (Germany); Wilms, A. [Ruhr-Universitaet Bochum, Bochum (Germany)
2009-03-15
The single-pion production reactions pp{yields}d{pi}{sup +}, pp{yields}np{pi}{sup +} and pp{yields}pp{pi}{sup 0} were measured at a beam momentum of 0.95GeV/c (T{sub p}{approx}400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and discussion of the np{pi}{sup +} channel, since the results on the other channels have already been published previously. The total and differential cross-sections obtained are compared to theoretical calculations. In contrast to the pp{pi}{sup 0} channel we observe in the np{pi}{sup +} channel a strong influence of the {delta} excitation. In particular, the pion angular distribution exhibits a (3 cos{sup 2}{theta}+1)-dependence, typical for a pure s-channel {delta} excitation and identical to that observed in the d{pi}{sup +} channel. Since the latter is understood by a s-channel resonance in the {sup 1} D{sub 2}pn partial wave, we discuss an analogous scenario for the pn{pi}{sup +} channel. (orig.)
Single-Pion Production in pp Collisions at 0.95 GeV/c (II)
El-Samad, S Abd; Brinkmann, K Th; Clement, H; Dietrich, M; Doroshkevich, E; Dshemuchadse, S; Ehrhardt, K; Erhardt, A; Eyrich, W; Filippi, A; Freiesleben, H; Fritsch, M; Geyer, R; Gillitzer, A; Hauffe, J; Hesselbarth, D; Jaekel, R; Jakob, B; Karsch, L; Kilian, K; Kress, J; Kuhlmann, E; Marcello, S; Marwinski, S; Meier, R; Möller, K; Morsch, H P; Naumann, Lutz; Ritman, J; Roderburg, E; Schoenmeier, P; Schulte-Wissermann, M; Schroeder, W; Stinzing, F; Sun, G Y; Waechter, J; Wagner, G J; Wagner, M; Weidlich, U; Wilms, A; Wirth, S; Zhang, G; Zupranski, P
2008-01-01
The single-pion production reactions $pp\\to d\\pi^+$, $pp\\to np\\pi^+$ and $pp\\to pp\\pi^0$ were measured at a beam momentum of 0.95 GeV/c ($T_p \\approx$ 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. Main emphasis is put on the presentation and discussion of the $np\\pi^+$ channel, since the results on the other channels have already been published previously. The total and differential cross sections obtained are compared to theoretical calculations. In contrast to the $pp\\pi^0$ channel we find in the $np\\pi^+$ channel a strong influence of the $\\Delta$ excitation already at this energy close to threshold. In particular we find a $(3 cos^2\\Theta + 1)$ dependence in the pion angular distribution, typical for a pure s-channel $\\Delta$ excitation a...
Double pion photoproduction off nuclei - are there effects beyond final-state interaction?
Maghrbi, Y; Lugert, S; Ahrens, J; Annand, J R M; Arends, H J; Beck, R; Bekrenev, V; Boillat, B; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R; Downie, E J; Dexler, P; Fil'kov, L V; Fix, A; Glazier, D I; Heid, E; Hornidge, D; Jahn, O; Jaegle, I; Kashevarov, V L; Keshelashvili, I; Knezevic, A; Kondratiev, A; Korolija, M; Kotulla, M; Krambrich, D; Krusche, B; Lang, M; Lisin, V; Livingston, K; MacGregor, I J D; Manley, D M; Martinez, M; McGeorge, J C; Mekterovic, D; Metag, V; Nefkens, B M K; Nikolaev, A; Novotny, R; Ostrick, M; Pedroni, P; Pheron, F; Polonski, A; Prakhov, S N; Price, J W; Rosner, G; Rost, M; Rostomyan, T; Schadmand, S; Schumann, S; Sober, D; Starostin, S; Supek, I; Thomas, A; Unverzagt, M; Watts, D P; Werthmueller, D; Zehr, F
2013-01-01
Photoproduction of $\\pi^{0}\\pi^{0}$ and $\\pi^{0}\\pi^{\\pm}$ pairs from nuclei has been measured over a wide mass range ($^2$H, $^{7}$Li, $^{12}$C, $^{40}$Ca, and $^{\\rm nat}$Pb) for photon energies from threshold to 600 MeV. The experiments were performed at the MAMI accelerator in Mainz, using the Glasgow photon tagging spectrometer and a 4$\\pi$ electromagnetic calorimeter consisting of the Crystal Ball and TAPS detectors. A shift of the pion-pion invariant mass spectra for heavy nuclei to small invariant masses has been observed for $\\pi^0$ pairs but also for the mixed-charge pairs. The precise results allow for the first time a model-independent analysis of the influence of pion final-state interactions. The corresponding effects are found to be large and must be carefully considered in the search for possible in-medium modifications of the $\\sigma$-meson. Results from a transport model calculation reproduce the shape of the invariant-mass distributions for the mixed-charge pairs better than for the neutral...
Exclusive measurement of two-pion production in the dd --> 4Hepipi reaction
Keleta, S; Bashkanov, M; Berlowski, M; Bogoslawsky, D; Calén, H; Clement, H; Demirors, L; Ekström, C; Fransson, K; Geren, L; Gustafsson, L; Höistad, B; Ivanov, G; Jacewicz, M; Jiganov, E; Johansson, T; Khakimova, O; Kren, F; Kullander, S; Kupsc, A; Kuzmin, A; Lindberg, K; Marciniewski, P; Morosov, B; Oelert, W; Pauly, C; Petren, H; Petukhov, Yu P; Povtorejko, A; Pricking, A; Ruber, R J M Y; Schonning, K; Scobel, W; Shafigullin, R; Shwartz, B; Skorodko, T; Sopov, V; Stepaniak, J; Tegner, P -E; Engblom, P Thorngren; Tikhomirov, V; Turowiecki, A; Wagner, G J; Wilkin, C; Wolke, M; Zabierowski, J; Zartova, I; Zlomanczuk, Yu
2009-01-01
The results from the first kinematically complete measurement of the dd --> 4Hepipi reaction are reported. The aim was to investigate a long standing puzzle regarding the origin of the peculiar pipi-invariant mass distributions appearing in double pion production in light ion collisions, the so-called ABC effect. The measurements were performed at the incident deuteron energies of 712 MeV and 1029 MeV, with the WASA detector assembly at CELSIUS in Uppsala, Sweden. We report the observation of a characteristic enhancement at low pipi-invariant mass at 712 MeV, the lowest energy yet. At the higher energy, in addition to confirming previous experimental observations, our results reveal a strong angular dependence of the pions in the overall centre of mass system. The results are qualitatively reproduced by a theoretical model, according to which the ABC effect is described as resulting from a kinematical enhancement in the production of the pion pairs from two parallel and independent NN--> dpi sub-processes.
Single-pion production in pp collisions at 0.95 GeV/c (II)
Abd El-Samad, S.; Bilger, R.; Brinkmann, K.-Th.; Clement, H.; Dietrich, M.; Doroshkevich, E.; Dshemuchadse, S.; Ehrhardt, K.; Erhardt, A.; Eyrich, W.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Geyer, R.; Gillitzer, A.; Hauffe, J.; Hesselbarth, D.; Jaekel, R.; Jakob, B.; Karsch, L.; Kilian, K.; Kress, J.; Kuhlmann, E.; Marcello, S.; Marwinski, S.; Meier, R.; Möller, K.; Morsch, H. P.; Naumann, L.; Ritman, J.; Roderburg, E.; Schönmeier, P.; Schulte-Wissermann, M.; Schroeder, W.; Stinzing, F.; Sun, G. Y.; Wächter, J.; Wagner, G. J.; Wagner, M.; Weidlich, U.; Wilms, A.; Wirth, S.; Zhang, G.; Zupranski, P.
2009-03-01
The single-pion production reactions pp rightarrow d π+_{} , pp rightarrow np π+_{} and pp rightarrow pp π0_{} were measured at a beam momentum of 0.95GeV/c ( T p ≈ 400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and discussion of the np π+_{} channel, since the results on the other channels have already been published previously. The total and differential cross-sections obtained are compared to theoretical calculations. In contrast to the pp π0_{} channel we observe in the np π+_{} channel a strong influence of the Δ excitation. In particular, the pion angular distribution exhibits a (3 cos2 Θ + 1) -dependence, typical for a pure s -channel Δ excitation and identical to that observed in the d π+_{} channel. Since the latter is understood by a s -channel resonance in the 1 D 2 pn partial wave, we discuss an analogous scenario for the pn π+_{} channel.
Ratios of Elastic Scattering of Pions from 3H and 3He
Briscoe, W J; Carter, R W C; Dhuga, K S; Matthews, S K; Nicholas, N J; Greene, S J; Nefkens, B M K; Price, J W; Isenhower, L D; Sadler, M E; Slaus, I; Supek, I
2002-01-01
We have measured the elastic-scattering ratios of normalized yields for charged pions from 3H and 3He in the backward hemisphere. At 180 MeV, we completed the angular distribution begun with our earlier measurements, adding six data points in the angular range of 119 deg to 169 deg in the pi-nucleus center of mass. We also measured an excitation function with data points at 142, 180, 220, and 256 MeV incident pion energy at the largest achievable angle for each energy between 160 deg and 170 deg in the pi-nucleus center of mass. This excitation function corresponds to the energies of our forward-hemisphere studies. The data, taken as a whole, show an apparent role reversal of the two charge-symmetric ratios r1 and r2 in the backward hemisphere. Also, for data > 100 deg we observe a strong dependence on the four-momentum transfer squared (-t) for all of the ratios regardless of pion energy or scattering angle, and we find that the superratio R data match very well with calculations based on the forward-hemisph...
Gauge invariant unitary theory for pion photoproduction
Energy Technology Data Exchange (ETDEWEB)
van Antwerpen, C.H.M.; Afnan, I.R. [Department of Physics, The Flinders University of South Australia, Bedford Park, South Australia, 5042 (Australia)
1995-08-01
The Ward-Takahashi identities are central to the gauge invariance of the photoproduction amplitude. Here we demonstrate that unitarity and in particular the inclusion of both the {pi}{ital N} and {gamma}{pi}{ital N} thresholds on equal footing yields a photoproduction amplitude that satisfies both two-body unitarity and the generalized Ward-Takahashi identities. The final amplitude is a solution of a set of coupled channel integral equations for the reactions {pi}{ital N}{r_arrow}{pi}{ital N} and {gamma}{ital N}{r_arrow}{pi}{ital N}.
Gauge invariant unitary theory for pion photoproduction
van Antwerpen, C. H. M.; Afnan, I. R.
1995-08-01
The Ward-Takahashi identities are central to the gauge invariance of the photoproduction amplitude. Here we demonstrate that unitarity and in particular the inclusion of both the πN and γπN thresholds on equal footing yields a photoproduction amplitude that satisfies both two-body unitarity and the generalized Ward-Takahashi identities. The final amplitude is a solution of a set of coupled channel integral equations for the reactions πN-->πN and γN-->πN.
Isospin breaking in the pion-nucleon scattering lengths
Hoferichter, Martin; Meißner, Ulf-G
2009-01-01
We analyze isospin breaking through quark mass differences and virtual photons in the pion-nucleon scattering lengths in all physical channels in the framework of covariant baryon chiral perturbation theory.
On the role of secondary pions in spallation targets
Energy Technology Data Exchange (ETDEWEB)
Mancusi, Davide [Paris-Saclay Univ., Gif-sur-Yvette (France). Den-Service d' Etude des Reacteurs et de Mathematiques Appliquees (SERMA); Lo Meo, Sergio [ENEA, Research Centre ' ' Ezio Clementel' ' , Bologna (Italy); INFN, Bologna (Italy); Colonna, Nicola [INFN, Bari (Italy); Boudard, Alain; David, Jean-Christophe; Leray, Sylvie [Paris-Saclay Univ., Gif-sur-Yvette (France). IRFU, CEA; Cortes-Giraldo, Miguel Antonio; Lerendegui-Marco, Jorge [Sevilla Univ. (Spain). Facultad de Fisica; Cugnon, Joseph [Liege Univ. (Belgium). AGO Dept.; Massimi, Cristian [INFN, Bologna (Italy); Bologna Univ. (Italy). Physics and Astronomy Dept.; Vlachoudis, Vasilis [European Organization for Nuclear Research (CERN), Geneva (Switzerland)
2017-05-15
We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the nTOF lead spallation target, irradiated with 20 GeV/c protons, neutral pions are involved in the production of ∝ 90% of the high-energy photons; charged pions participate in ∝ 40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets. (orig.)
Dynamical model of electroweak pion production in the resonance region
Sato, T; Kubodera, K; Lee, T S H
2006-01-01
In this report, we will briefly review the dynamical model of pion electroweak production reactions in the $\\Delta$ resonance region and report on our study of neutrino-nucleus reactions based on this model.
Cumulative pion production via successive collisions in nuclear medium
Motornenko, A
2016-01-01
Production of pions in proton-nucleus (p+A) reactions outside of a kinematical boundary of proton-nucleon collisions, the so-called cumulative effect, is studied. The kinematical restrictions on pions emitted in backward direction in the target rest frame are analyzed. It is shown that cumulative pion production requires a presence of massive baryonic resonances that are produced during successive collisions of projectile with nuclear nucleons. After each successive collision the mass of created resonance may increase and, simultaneously, its longitudinal velocity decreases. Simulations within Ultra relativistic Quantum Molecular Dynamics model reveals that successive collisions of baryonic resonances with nuclear nucleons plays the dominant role in cumulative pion production in p+A reactions.
Quark and pion effective couplings from polarization effects
Braghin, Fabio L
2016-01-01
A flavor SU(2) effective model for pions and quarks is derived by considering polarization effects departing from the usual quark-quark effective interaction induced by dressed gluon exchange, i.e. a global color model for QCD. For that, the quark field is decomposed into a component that yields light mesons and the quark-antiquark condensate, being integrated out by means of the auxiliary field method, and another component which yields constituent quarks. Within a longwavelength and weak quark field expansion (or large quark effective mass expansion) of a quark determinant, the leading terms are found up to the second order in a zero order derivative expansion, by neglecting vector mesons that are considerably heavier than the pion. Pions are considered in the structureless limit and, besides the chiral invariant pion self interaction terms that reproduce previously derived expressions, symmetry breaking terms are also presented. The leading chiral quark-quark effective couplings are also found correspondin...
Study of $\\tau$ Decays to Six Pions and Neutrino
Anastassov, A; Eckhart, E; Gan, K K; Gwon, C; Hart, T; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pedlar, T K; Schwarthoff, H; Thayer, J B; Von Törne, E; Zoeller, M M; Richichi, S J; Severini, H; Skubic, P L; Undrus, A; Chen, S; Fast, J; Hinson, J W; Lee, J; Miller, D H; Shibata, E I; Shipsey, I P J; Pavlunin, V; Cronin-Hennessy, D; Lyon, A L; Thorndike, E H; Jessop, C P; Savinov, V; Coan, T E; Fadeev, V; Maravin, Y; Narsky, I; Stroynowski, R; Ye, J; Wlodek, T; Artuso, M; Ayad, R; Boulahouache, C; Bukin, K; Dambasuren, E; Karamov, S; Majumder, G; Moneti, G C; Mountain, R; Schuh, S; Skwarnicki, T; Stone, S; Viehhauser, G; Wang, J C; Wolf, A; Wu, J; Kopp, S E; Mahmood, A H; Csorna, S E; Danko, I; McLean, K W; Xu, Z; Godang, R; Bonvicini, G; Cinabro, D; Dubrovin, M; McGee, S; Zhou, G J; Lipeles, E; Pappas, S P; Schmidtler, M; Shapiro, A; Sun, W M; Weinstein, A J; Würthwein, F; Jaffe, D E; Masek, G E; Paar, H P; Potter, E M; Prell, S; Asner, D M; Eppich, A; Hill, T S; Morrison, R J; Briere, R A; Chen, G P; Ford, W T; Gritsan, A; Roy, J D; Smith, J G; Alexander, J P; Baker, R; Bebek, C; Berger, B E; Berkelman, K; Blanc, F; Boisvert, V; Cassel, David G; Drell, P S; Ecklund, K M; Ehrlich, R; Foland, A D; Gaidarev, P B; Galik, R S; Gibbons, L K; Gittelman, B; Gray, S W; Hartill, D L; Heltsley, B K; Hopman, P I; Hsu, L; Jones, C D; Kreinick, D L; Lohner, M; Magerkurth, A; Meyer, T O; Mistry, N B; Nordberg, E; Patterson, J R; Peterson, D; Riley, D; Romano, A; Thayer, J G; Urner, D; Valant-Spaight, B L; Warburton, A; Avery, P; Prescott, C; Rubiera, A I; Stöck, H; Yelton, J; Brandenburg, G; Ershov, A; Gao, Y S; Kim, D Y J; Wilson, R; Bergfeld, T; Eisenstein, B I; Ernst, J; Gladding, G E; Gollin, G D; Hans, R M; Johnson, E; Karliner, I; Marsh, M A; Palmer, M; Plager, C; Sedlack, C; Selen, M; Thaler, J J; Williams, J; Edwards, K W; Janicek, R; Patel, P M; Sadoff, A J; Ammar, R; Bean, A; Besson, D; Zhao, X; Anderson, S; Frolov, V V; Kubota, Y; Lee, S J; Mahapatra, R; O'Neill, J J; Poling, R A; Riehle, T; Smith, A; Stepaniak, C J; Urheim, J; Ahmed, S; Alam, M S; Athar, S B; Jian, L; Ling, L; Saleem, M; Timm, S; Wappler, F
2001-01-01
The $\\tau$ decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are ${\\cal B}(\\tau^-\\to 2\\pi^-\\pi^+3\\pi^0\
On the role of secondary pions in spallation targets
Mancusi, Davide; Colonna, Nicola; Boudard, Alain; Cortés-Giraldo, Miguel Antonio; Cugnon, Joseph; David, Jean-Christophe; Leray, Sylvie; Lerendegui-Marco, Jorge; Massimi, Cristian; Vlachoudis, Vasilis
2016-01-01
We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the n_TOF lead spallation target, irradiated with 20-GeV/c protons, neutral pions are involved in the production of ~90% of the high-energy photons; charged pions participate in ~40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets.
Weak Boson Production Amplitude Zeros; Equalities of the Helicity Amplitudes
Mamedov, F
2002-01-01
We investigate the radiation amplitude zeros exhibited by many Standard Model amplitudes for triple weak gauge boson production processes. We show that $WZ\\gamma$ production amplitudes have especially rich structure in terms of zeros, these amplitudes have zeros originating from several different sources. It is also shown that TYPE I current null zone is the special case of the equality of the specific helicity amplitudes.
Energy Technology Data Exchange (ETDEWEB)
Blomberg, Adam [Temple Univ., Philadelphia, PA (United States)
2016-12-01
Non-spherical components of the nucleon wave function are measured through p(e,e'p)π^{0} experiment at the Δ^{+}(1232) resonance for Q^{2} = 0.04, 0.09, and 0.13 (GeV=c)^{2} utilizing the Jefferson National Accelerator Facility (JLab) pulsed beam and Hall A spectrometers. The new data extend the measurements of the Coulomb quadrupole amplitude to the lowest momentum transfer ever reached. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations that include pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements indicate that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. The Coulomb to magnetic multipole ratio (CMR) and generalized polarizability (GP) of the nucleon are also measured through virtual Compton scattering (VCS) for Q^{2} = 0.2(GeV=c)^{2} utilizing the Mainz Microtron (MAMI) continuous beam and A1 spectrometers. This data represents the first low Q^{2} GP measurement at the Δ^{+}(1232) resonance. The GP measurement explores a region where previous data and theoretical calculations disagree. The CMR measurement will be the first VCS extraction to compare with world data generated through pion electroproduction. The Dispersion Relation (DR) model used for the VCS extraction provides a new theoretical framework for the data signal and backgrounds that is largely independent from the pion electroproduction models. The independence of the DR from the traditional models provides a strong crosscheck on the ability of the models to isolate the data signal.
Energy Technology Data Exchange (ETDEWEB)
Hilt, Marius
2011-12-13
This thesis is concerned with pion photoproduction (PPP) and pion electroproduction (PEP) in the framework of manifestly Lorentz-invariant baryon chiral perturbation theory. For that purpose two different approaches are used. Firstly, a one-loop-order calculation up to chiral order O(q{sup 4}) including pions and nucleons as degrees of freedom, is performed to describe the energy dependence of the reactions over a large range. To improve the dependence on the virtuality of the photon in PEP, in a second approach vector mesons are included as explicit degrees of freedom. The latter calculation includes one-loop contributions up to chiral order O(q{sup 3}). Only three of the four physical processes of PPP and PEP can be accessed experimentally. These reactions are measured at several different facilities, e.g. Mainz, Bonn, or Saskatoon. The data obtained there are used to explore the limits of chiral perturbation theory. This thesis is the first complete manifestly Lorentz-invariant calculation up to order O(q{sup 4}) for PPP and PEP, and the first calculation ever for these processes including vector mesons explicitly. Beside the calculation of physical observables, a partial wave decomposition is performed and the most important multipoles are analyzed. They may be extracted from the calculated amplitudes and allow one to examine the nucleon and {delta} resonances. The number of diagrams one has to calculate is very large. In order to handle these expressions, several routines were developed for the computer algebra system Mathematica. For the multipole decomposition, two different programs are used. On the one hand, a modified version of the so-called {chi}MAID has been employed. On the other hand, similar routines were developed for Mathematica. In the end, the different calculations are compared with respect to their applicability to PPP and PEP.
Periods and Superstring Amplitudes
Stieberger, S
2016-01-01
Scattering amplitudes which describe the interaction of physical states play an important role in determining physical observables. In string theory the physical states are given by vibrations of open and closed strings and their interactions are described (at the leading order in perturbation theory) by a world-sheet given by the topology of a disk or sphere, respectively. Formally, for scattering of N strings this leads to N-3-dimensional iterated real integrals along the compactified real axis or N-3-dimensional complex sphere integrals, respectively. As a consequence the physical observables are described by periods on M_{0,N} - the moduli space of Riemann spheres of N ordered marked points. The mathematical structure of these string amplitudes share many recent advances in arithmetic algebraic geometry and number theory like multiple zeta values, single-valued multiple zeta values, Drinfeld, Deligne associators, Hopf algebra and Lie algebra structures related to Grothendiecks Galois theory. We review the...
Quantitative Seismic Amplitude Analysis
Dey, A. K.
2011-01-01
The Seismic Value Chain quantifies the cyclic interaction between seismic acquisition, imaging and reservoir characterization. Modern seismic innovation to address the global imbalance in hydrocarbon supply and demand requires such cyclic interaction of both feed-forward and feed-back processes. Currently, the seismic value chain paradigm is in a feed-forward mode. Modern seismic data now have the potential to yield the best images in terms of spatial resolution, amplitude accuracy, and incre...
Di-photon resonance and Dark Matter as heavy pions
Redi, Michele; Tesi, Andrea; Vigiani, Elena
2016-05-13
We analyse confining gauge theories where the 750 GeV di-photon resonance is a composite techni-pion that undergoes anomalous decays into SM vectors. These scenarios naturally contain accidentally stable techni-pions Dark Matter candidates. The di-photon resonance can acquire a larger width by decaying into Dark Matter through the CP-violating $\\theta$-term of the new gauge theory reproducing the cosmological Dark Matter density as thermal relic.
The Onset of Quark-Hadron Duality in Pion Electroproduction
Navasardyan, T; Ahmidouch, A; Angelescu, T; Arrington, J; Asaturyan, R; Baker, O K; Benmouna, N; Bertoncini, C; Blok, H P; Bosted, P E; Breuer, H; Böglin, W; Christy, M E; Connell, S H; Cui, Y; Dalton, M M; Danagulyan, S; Day, D; Dodario, T; Dunne, J A; Dutta, D; Ent, R; Fenker, H C; Frolov, V V; Gan, L; Gaskell, D; Hafidi, K; Hinton, W; Holt, R J; Horn, T; Huber, G M; Hungerford, E; Jiang, X; Jones, M; Joo, K; Kalantarians, N; Kelly, J J; Keppel, C E; Khayari, N E; Kinney, E R; Kubarovski, V; Li, Y; Liang, Y; Malace, S; Markowitz, P; McGrath, E; McKee, P; Meekins, D G; Mkrtchyan, H; Moziak, B; Niculescu, G; Niculescu, I; Opper, A K; Ostapenko, T; Reimer, P; Reinhold, J; Roche, J; Rock, S E; Schulte, E; Segbefia, E; Smith, C; Smith, G R; Stoler, P; Tadevosyan, V; Tang, L; Ungaro, M; Uzzle, A; Vidakovic, S; Villano, A; Vulcan, W F; Wang, M; Warren, G; Wesselmann, F; Wojtsekhowski, B; Wood, S A; Xu, C; Yuan, L; Zheng, X; Zhu, H
2007-01-01
A large data set of charged-pion electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark-to- pion production mechanisms.
The Electromagnetic Mass Differences of Pions and Kaons
Donoghue, J F; Donoghue, John F.; Perez, Antonio F.
1997-01-01
We use the Cottingham method to calculate the pion and kaon electromagnetic mass differences with as few model dependent inputs as possible. The constraints of chiral symmetry at low energy, QCD at high energy and experimental data in between are used in the dispersion relation. We find excellent agreement with experiment for the pion mass difference. The kaon mass difference exhibits a strong violation of the lowest order prediction of Dashen's theorem, in qualitative agreement with several other recent calculations.
Effects of Nonlocal One-Pion-Exchange Potential in Deuteron
Forest, J. L.
1999-01-01
The off-shell aspects of the one-pion-exchange potential (OPEP) are discussed. Relativistic Hamiltonians containing relativistic kinetic energy, relativistic OPEP with various off-shell behaviors and Argonne $v_{18}$ short-range parameterization are used to study the deuteron properties. The OPEP off-shell behaviors depend on whether a pseudovector or pseudoscalar pion-nucleon coupling is used and are characterized by a parameter $\\mu$. We study potentials having $\\mu$=-1, 0 and +1 and we fin...
The transverse spin structure of the pion at short distances
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Szymanowski, Lech [Soltan Inst. for Nuclear Studies, Warsaw (Poland); Ecole Polytechnique, CNRS, Palaiseau (France). Centre de Physique Theorique; Paris-Sud Univ., CNRS, Orsay (France). Lab. de Physique Theorique
2010-03-15
We study the form factors of the quark tensor currents in the pion at large squared momentum transfer Q{sup 2}. It turns out that certain form factors can be evaluated using collinear factorization, whereas others receive important contributions from the end-point regions of the longitudinal quark momenta in the pion. We derive simple analytic expressions for the dominant terms at high Q{sup 2} and illustrate them numerically. (orig.)
Stopping pions in high-energy nuclear cascades.
Jones, W. V.; Johnson, D. P.; Thompson, J. A.
1973-01-01
Results of Monte Carlo calculations for the number and energy spectra of charged pions from nuclear-electromagnetic cascades developing in rock are presented for primary hadron energies ranging from 3 to 3000 GeV. These spectra are given as functions of the longitudinal depth in the absorber and the lateral distance from the cascade axis. The number of charged pions which stop in the absorber increases with the primary energy of the hadron initiating the cascade.
Di-photon resonance and Dark Matter as heavy pions
Redi, Michele; Tesi, Andrea; Vigiani, Elena
2016-01-01
We analyse confining gauge theories where the 750 GeV di-photon resonance is a composite techni-pion that undergoes anomalous decays into SM vectors. These scenarios naturally contain accidentally stable techni-pions Dark Matter candidates. The di-photon resonance can acquire a larger width by decaying into Dark Matter through the CP-violating $\\theta$-term of the new gauge theory reproducing the cosmological Dark Matter density as thermal relic.
The transverse spin structure of the pion at short distances
Diehl, Markus
2010-01-01
We study the form factors of the quark tensor currents in the pion at large squared momentum transfer Q^2. It turns out that certain form factors can be evaluated using collinear factorization, whereas others receive important contributions from the end-point regions of the longitudinal quark momenta in the pion. We derive simple analytic expressions for the dominant terms at high Q^2 and illustrate them numerically.
Pion transverse charge density from timelike form factor data
Energy Technology Data Exchange (ETDEWEB)
Gerald Miller, Mark Strikman, Christian Weiss
2011-01-01
The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from e+e- annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of ~10% at a distance b ~ 0.1 fm, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width rho meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion's partonic wave function, which can be probed in other high-momentum transfer processes.
Single pion electro- and neutrino production on heavy targets
Energy Technology Data Exchange (ETDEWEB)
Paschos, E. A. [Theoretische Physik III, University of Dortmund, D-44221 Dortmund (Germany); Schienbein, I. [Laboratoire de Physique Subatomique et de Cosmologie, Universite Joseph Fourier/CNRS-IN2P3, 53 Avenue des Martyrs, F-38026 Grenoble (France); Yu, J.Y. [Southern Methodist University, Dallas, Texas 75275 (United States)
2007-04-15
We present a calculation of single pion electroproduction cross sections on heavy targets in the kinematic region of the {delta}(1232) resonance. Final state interactions of the pions are taken into account using the pion multiple scattering model of Adler, Nussinov and Paschos (ANP model). For electroproduction and neutral current reactions we obtain results for carbon, oxygen, argon and iron targets and find a significant reduction of the W-spectra for {pi}{sup 0} as compared to the free nucleon case. On the other hand, the charged pion spectra are only little affected by final state interactions. Measurements of such cross sections with the CLAS detector at JLAB could help to improve our understanding of pion rescattering effects and serve as important/valuable input for calculations of single pion neutrino production on heavy targets relevant for current and future long baseline neutrino experiments. Two ratios, in Eq. (3.8) and (3.10), will test important properties of the model. (authors)
Gravitational wave from dark sector with dark pion
Tsumura, Koji; Yamada, Masatoshi; Yamaguchi, Yuya
2017-07-01
In this work, we investigate the spectra of gravitational waves produced by chiral symmetry breaking in dark quantum chromodynamics (dQCD) sector. The dark pion (π) can be a dark matter candidate as weakly interacting massive particle (WIMP) or strongly interacting massive particle (SIMP). For a WIMP scenario, we introduce the dQCD sector coupled to the standard model (SM) sector with classical scale invariance and investigate the annihilation process of the dark pion via the 2π → 2 SM process. For a SIMP scenario, we investigate the 3π → 2π annihilation process of the dark pion as a SIMP using chiral perturbation theory. We find that in the WIMP scenario the gravitational wave background spectra can be observed by future space gravitational wave antennas. On the other hand, when the dark pion is the SIMP dark matter with the constraints for the chiral perturbative limit and pion-pion scattering cross section, the chiral phase transition becomes crossover and then the gravitational waves are not produced.
Dispersion relations with crossing symmetry for pipi D and F wave amplitudes
Kaminski, R.
2011-01-01
A set of once subtracted dispersion relations with imposed crossing symmetry condition for the pipi D- and F-wave amplitudes is derived and analyzed. An example of numerical calculations in the effective two pion mass range from the threshold to 1.1 GeV is presented. It is shown that these new dispersion relations impose quite strong constraints on the analyzed pipi interactions and are very useful tools to test the pipi amplitudes. One of the goals of this work is to provide a complete set o...
Topographic quantitative EEG amplitude in recovered alcoholics.
Pollock, V E; Schneider, L S; Zemansky, M F; Gleason, R P; Pawluczyk, S
1992-05-01
Topographic measures of electroencephalographic (EEG) amplitude were used to compare recovered alcoholics (n = 14) with sex- and age-matched control subjects. Delta, alpha, and beta activity did not distinguish the groups, but regional differences in theta distribution did. Recovered alcoholics showed more uniform distributions of theta amplitudes in bilateral anterior and posterior regions compared with controls. Because a minimum of 5 years had elapsed since the recovered alcoholic subjects fulfilled DSM-III-R criteria for alcohol abuse or dependence, it is unlikely these EEG theta differences reflect the effects of withdrawal.
Fatigue Reliability under Multiple-Amplitude Loads
DEFF Research Database (Denmark)
Talreja, R.
1979-01-01
A method to determine the fatigue of structures subjected to multiple-amplitude loads is presented. Unlike the more common cumulative damage methods, which are usually based on fatigue life data, the proposed method is based on tensile strength data. Assuming the Weibull distribution...... for the initial tensile strength and the fatigue life, the probability distributions for the residual tensile strength in both the crack initiation and the crack propagation stages of fatigue are determined. The method is illustrated for two-amplitude loads by means of experimental results obtained by testing...
Neutron skin of (208)pb from coherent pion photoproduction.
Tarbert, C M; Watts, D P; Glazier, D I; Aguar, P; Ahrens, J; Annand, J R M; Arends, H J; Beck, R; Bekrenev, V; Boillat, B; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R; Downie, E J; Foehl, K; Grabmayr, P; Gregor, R; Heid, E; Hornidge, D; Jahn, O; Kashevarov, V L; Knezevic, A; Kondratiev, R; Korolija, M; Kotulla, M; Krambrich, D; Krusche, B; Lang, M; Lisin, V; Livingston, K; Lugert, S; MacGregor, I J D; Manley, D M; Martinez, M; McGeorge, J C; Mekterovic, D; Metag, V; Nefkens, B M K; Nikolaev, A; Novotny, R; Owens, R O; Pedroni, P; Polonski, A; Prakhov, S N; Price, J W; Rosner, G; Rost, M; Rostomyan, T; Schadmand, S; Schumann, S; Sober, D; Starostin, A; Supek, I; Thomas, A; Unverzagt, M; Walcher, Th; Zana, L; Zehr, F
2014-06-20
Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.) fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.) fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.) fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.
The neutron skin of $^{208}$Pb from coherent pion photoproduction
Tarbert, C M; Glazier, D I; Aguar, P; Ahrens, J; Annand, J R M; Arends, H J; Beck, R; Bekrenev, V; Boillat, B; Braghieri, A; Branford, D; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R; Downie, E J; Foehl, K; Grabmayr, P; Gregor, R; Heid, E; Hornidge, D; Jahn, O; Kashevarov, V L; Knezevic, A; Kondratiev, R; Korolija, M; Kotulla, M; Krambrich, D; Krusche, B; Lang, M; Lisin, V; Livingston, K; Lugert, S; MacGregor, I J D; Manley, D M; Martinez, M; McGeorge, J C; Mekterovic, D; Metag, V; Nefkens, B M K; Nikolaev, A; Novotny, R; Owens, R O; Pedroni, P; Polonski, A; Prakhov, S N; Price, J W; Rosner, G; Rost, M; Rostomyan, T; Schadmand, S; Schumann, S; Sober, D; Starostin, A; Supek, I; Thomas, A; Unverzagt, M; Walcher, Th; Zehr, F
2013-01-01
Information on the size and shape of the neutron skin on $^{208}$Pb has been extracted from coherent pion photoproduction cross sections measured using the Crystal Ball together with the Glasgow tagger at the MAMI electron beam facility. Exploiting an interpolated fit of a theoretical model to the measured cross sections the half-height radius and diffuseness of the neutron distribution are found to be 6.77$\\pm 0.03(stat)$ fm and 0.55$\\pm 0.01(stat)$$^{+0.00}_{-0.025}(sys)$ fm respectively, corresponding to a neutron skin thickness $\\Delta r_{np}$=0.19$\\pm 0.03(stat)$$^{+0.00}_{-0.03}(sys)$ fm. The results give the first successful extraction of a neutron skin with an electromagnetic probe and indicate the skin of $^{208}$Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron rich matter.
Pion-induced production of the $Z_c(3900)$ off nuclear target
Huang, Yin; Liu, Xiang; Zhang, Hong Fei; Xie, Ju Jun; Chen, Xu Rong
2015-01-01
We investigate the possibility to study the charmonium-like state $Z_c(3900)$ through the pion-induced production off nuclear target. By using high-energy pion beam, the $Z_c(3900)$ can be produced off proton or nucleus though the Primakoff effect. The production amplitude is calculated in an effective Lagrangian approach combined with the vector dominance model. The total cross sections of the $p(\\pi^-, Z^-_c(3900))$ and $p(\\pi^-, Z^-_c(3900)\\to J/\\psi\\pi^-)$ reactions are calculated, which order of magnitude is about 0.1 and 0.01nb, respectively, with an assumption of branch ratio 10\\% for the $Z_c(3900)$ decay in $J/\\psi\\pi$ channel. If proton target is replaced by nuclear target, the production of the $Z_c(3900)$ enhances obviously. The predicted total cross sections for the $A(\\pi^-, Z^-_c(3900))$ and $A(\\pi^-, Z^-_c(3900)\\to J/\\psi\\pi^-)$ reactions with $A=^{12}$C or $^{208}$Pb are on the order of magnitude of 100 and 10 nb, respectively, which is about one thousand times larger than the cross sections ...
Pion polarizabilities from a γ γ →π π analysis
Dai, Ling-Yun; Pennington, M. R.
2016-12-01
We present results for pion polarizabilities predicted using dispersion relations from our earlier amplitude analysis of world data on two photon production of meson pairs. The helicity-zero polarizabilities are rather stable and insensitive to uncertainties in cross-channel exchanges. The need is first to confirm the recent result on (α1-β1) for the charged pion by COMPASS at CERN to an accuracy of 10% by measuring the γ γ →π+π- cross section to an uncertainty of 1%. Then the same polarizability, but for π0, is fixed to be (α1-β1)π0=(0.9 ±0.2 )×10-4 fm3 . By analyzing the correlation between uncertainties in the meson polarizability and those in γ γ cross sections, we suggest experiments need to measure these cross sections between √{s }≃350 and 600 MeV. The π0π0 cross section then makes the (α2-β2)π0 the easiest helicity-two polarizability to determine.
Aspects of the ETH model of the pion-nucleon interaction
Matsinos, Evangelos
2013-01-01
The ETH model of the pion-nucleon ($\\pi N$) interaction contains $t$-channel $\\sigma$- and $\\rho$-exchange graphs, as well as the $s$- and $u$-channel contributions with all the well-established $s$ and $p$ baryon states with masses below $2$ GeV as virtual particles; the model amplitudes obey crossing symmetry and isospin invariance. In the present work, we give all the analytical expressions for the model contributions to the $K$-matrix elements up to (and including) the $f$ waves. We also revisit the subject of the $\\pi N$ $\\Sigma$ term and obtain a prediction for the scalar form factor $\\sigma(2 m_c^2)$ ($m_c$ is the mass of the charged pion) from the results of a recent partial-wave analysis of meson-factory $\\pi^\\pm p$ elastic-scattering measurements below $100$ MeV: $\\sigma(2 m_c^2) = 69.2 \\pm 2.1$ MeV. After correcting a few flaws in Olsson's 2000 paper, we obtain almost the same result when using his method, featuring the evaluation of $\\sigma(2 m_c^2)$ (predominantly) from low-energy constants of th...
Institute of Scientific and Technical Information of China (English)
Chen Xiao-Fan; Yang Xue-Dong; Hah Ling
2004-01-01
A two-pion correlation function at small relative momentum for pion sources with transverse and longitudinal expansions in relativistic heavy ion collisions is obtained using two-pion interferometry at small relative momentum,and the relations between the real and apparent parameters of the pion source are given. The relations can be used to extract both the temperature and the transverse and longitudinal expansion velocities of pion sources and to verify the correctness of relativistic transformation T' = T√1- v2 of temperature in relativistic statistical mechanics and thermodynamics.
Nucleon polarisabilities at and beyond physical pion masses
Energy Technology Data Exchange (ETDEWEB)
Griesshammer, Harald W. [The George Washington University, Institute for Nuclear Studies, Department of Physics, Washington, DC (United States); McGovern, Judith A. [The University of Manchester, School of Physics and Astronomy, Manchester (United Kingdom); Phillips, Daniel R. [Ohio University, Department of Physics and Astronomy and Institute of Nuclear and Particle Physics, Athens, OH (United States)
2016-05-15
We examine the results of Chiral Effective Field Theory (χEFT) for the scalar- and spin-dipole polarisabilities of the proton and neutron, both for the physical pion mass and as a function of m{sub π}. This provides chiral extrapolations for lattice QCD polarisability computations. We include both the leading and subleading effects of the nucleon's pion cloud, as well as the leading ones of the Δ (1232)-resonance and its pion cloud. The analytic results are complete at N{sup 2}LO in the δ counting for pion masses close to the physical value, and at leading order for pion masses similar to the Delta-nucleon mass splitting. In order to quantify the truncation error of our predictions and fits as 68% degree-of-belief intervals, we use a Bayesian procedure recently adapted to EFT expansions. At the physical point, our predictions for the spin polarisabilities are, within respective errors, in good agreement with alternative extractions using experiments and dispersion-relation theory. At larger pion masses we find that the chiral expansion of all polarisabilities becomes intrinsically unreliable as m{sub π} approaches about 300 MeV -as has already been seen in other observables. χEFT also predicts a substantial isospin splitting above the physical point for both the electric and magnetic scalar polarisabilities; and we speculate on the impact this has on the stability of nucleons. Our results agree very well with emerging lattice computations in the realm where χEFT converges. Curiously, for the central values of some of our predictions, this agreement persists to much higher pion masses. We speculate on whether this might be more than a fortuitous coincidence. (orig.)
Measurement of Inverse Pion Photoproduction at Energies Spanning the N(1440) Resonance
Shafi, A; Strakovsky, I I; Briscoe, W J; Nefkens, B M K; Allgower, C E; Arndt, R A; Bekrenev, V; Bennhold, C; Clajus, M; Comfort, J R; Craig, K; Grosnick, D P; Isenhower, D; Knecht, N; Koetke, D D; Kulbardis, A; Kozlenko, N; Kruglov, S; Lolos, G J; Lopatin, I; Manley, D M; Manweiler, R; Marusic, A; McDonald, S; Olmsted, J; Papandreou, Z; Peaslee, D; Phaisangittisakul, N; Price, J W; Ramírez, A F; Sadler, M; Spinka, H; Stanislaus, T D S; Starostin, A; Staudenmaier, H M; Supek, I; Tippens, W B; Workman, R L; Workman, and R.L.
2004-01-01
Differential cross sections for the process pi^- p -> gamma n have been measured at Brookhaven National Laboratory's Alternating Gradient Synchrotron with the Crystal Ball multiphoton spectrometer. Measurements were made at 18 pion momenta from 238 to 748 MeV/c, corresponding to E_gamma for the inverse reaction from 285 to 769 MeV. The data have been used to evaluate the gamma n multipoles in the vicinity of the N(1440) resonance. We compare our data and multipoles to previous determinations. A new three-parameter SAID fit yields 36 +/- 7 (GeV)^-1/2 X 10^-3 for the A^n_1/2 amplitude of the P_11.
Fanelli, C; Hamilton, D J; Salme, G; Wojtsekhowski, B; Ahmidouch, A; Annand, J R M; Baghdasaryan, H; Beaufait, J; Bosted, P; Brash, E J; Butuceanu, C; Carter, P; Christy, E; Chudakov, E; Danagoulian, S; Day, D; Degtyarenko, P; Ent, R; Fenker, H; Fowler, M; Frlez, E; Gaskell, D; Gilman, R; Horn, T; Huber, G M; de Jager, C W; Jensen, E; Jones, M K; Kelleher, A; Keppel, C; Khandaker, M; Kohl, M; Kumbartzki, G; Lassiter, S; Li, Y; Lindgren, R; Lovelace, H; Luo, W; Mack, D; Mamyan, V; Margaziotis, D J; Markowitz, P; Maxwell, J; Mbianda, G; Meekins, D; Meziane, M; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Mulholland, J; Nelyubin, V; Pentchev, L; Perdrisat, C F; Piasetzky, E; Prok, Y; Puckett, A J R; Punjabi, V; Shabestari, M; Shahinyan, A; Slifer, K; Smith, G; Solvignon, P; Subedi, R; Wesselmann, F R; Wood, S; Ye, Z; Zheng, X
2015-01-01
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The WACS polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of \\cma$= 70^\\circ$. The longitudinal transfer \\KLL, measured to be $0.645 \\pm 0.059 \\pm 0.048$, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is $\\sim$3 times larger than predicted by the GPD-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Renormalizing the Lippmann-Schwinger equation for the one pion exchange potential
Eiras, D; Eiras, Dolors; Soto, Joan
2003-01-01
We address the question whether the cut-off dependence, which has to be introduced in order to properly define the Lippmann-Schwinger equation for the one pion exchange potential plus local (delta-function) potentials, can be removed (up to inverse powers of it) by a suitable tuning of the various (bare) coupling constants. We prove that this is indeed so both for the spin singlet and for the spin triplet channels. However, the latter requires such a strong cut-off dependence of the coupling constant associated to the non-local term which breaks orbital angular momentum conservation, that the renormalized amplitude lacks from partial wave mixing. We argue that this is an indication that this term must be treated perturbatively.
Two-pion exchange and strong form-factors in covariant field theories
Ramalho, G; Peña, M T
1999-01-01
In this work improvements to the application of the Gross equation to nuclear systems are tested. In particular we evaluate the two pion exchange diagrams, including the crossed-box diagram, using models developed within the spectator-on-mass-shell covariant formalism. We found that the form factors used in these models induce spurious contributions that violate the unitary cut requirement. We tested then some alternative form-factors in order to preserve the unitarity condition. With this new choice, the difference between the exact and the spectator-on-mass-shell amplitudes is of the order of the one boson scalar exchange, supporting the idea that this difference may be parameterized by this type of terms.
Hadronic Light by Light Contributions to the Muon Anomalous Magnetic Moment With Physical Pions
Jin, Luchang; Christ, Norman; Hayakawa, Masashi; Izubuchi, Taku; Lehner, Christoph
2015-01-01
The current measurement of muonic $g - 2$ disagrees with the theoretical calculation by about 3 standard deviations. Hadronic vacuum polarization (HVP) and hadronic light by light (HLbL) are the two types of processes that contribute most to the theoretical uncertainty. The current value for HLbL is still given by models. I will describe results from a first-principles lattice calculation with a 139 MeV pion in a box of 5.5 fm extent. Our current numerical strategies, including noise reduction techniques, evaluating the HLbL amplitude at zero external momentum transfer, and important remaining challenges, in particular those associated with finite volume effects, will be discussed.
Transverse target single-spin asymmetry in inclusive electroproduction of charged pions and kaons
Energy Technology Data Exchange (ETDEWEB)
Airapetian, A. [Giessen Univ. (Germany). 2. Physikalisches Inst.; Michigan Univ., Ann Arbor, MI (United States). Randall Laboratory of Physics; Akopov, N. [Yerevan Physics Institute (Argentina); Akopov, Z. [DESY Hamburg (Germany)] [and others; Collaboration: HERMES Collaboration
2013-10-15
Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle {psi} about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum P{sub T} relative to the direction of the incident beam, and the Feynman variable x{sub F}. The sin {psi} amplitudes are positive for {pi}{sup +} and K{sup +}, slightly negative for {pi}{sup -} consistent with zero for K{sup -}, with particular P{sub T} but weak x{sub F} dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer.
High-Precision Determination of the Pion-Nucleon σ Term from Roy-Steiner Equations
Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.
2015-08-01
We present a determination of the pion-nucleon (π N ) σ term σπ N based on the Cheng-Dashen low-energy theorem (LET), taking advantage of the recent high-precision data from pionic atoms to pin down the π N scattering lengths as well as of constraints from analyticity, unitarity, and crossing symmetry in the form of Roy-Steiner equations to perform the extrapolation to the Cheng-Dashen point in a reliable manner. With isospin-violating corrections included both in the scattering lengths and the LET, we obtain σπ N=(59.1 ±1.9 ±3.0 ) MeV =(59.1 ±3.5 ) MeV , where the first error refers to uncertainties in the π N amplitude and the second to the LET. Consequences for the scalar nucleon couplings relevant for the direct detection of dark matter are discussed.
Exclusive production of pion and kaon meson pairs in two photon collisions at LEP
ALEPH Collaboration; Heister, A.; Schael, S.; Barate, R.; Brunelière, R.; de Bonis, I.; Decamp, D.; Goy, C.; Jezequel, S.; Lees, J.-P.; Martin, F.; Merle, E.; Minard, M.-N.; Pietrzyk, B.; Trocmé, B.; Bravo, S.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Martinez, M.; Pacheco, A.; Ruiz, H.; Colaleo, A.; Creanza, D.; de Filippis, N.; de Palma, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Tricomi, A.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Abbaneo, D.; Barklow, T.; Buchmüller, O.; Cattaneo, M.; Clerbaux, B.; Drevermann, H.; Forty, R. W.; Frank, M.; Gianotti, F.; Hansen, J. B.; Harvey, J.; Hutchcroft, D. E.; Janot, P.; Jost, B.; Kado, M.; Mato, P.; Moutoussi, A.; Ranjard, F.; Rolandi, L.; Schlatter, D.; Sguazzoni, G.; Teubert, F.; Valassi, A.; Videau, I.; Badaud, F.; Dessagne, S.; Falvard, A.; Fayolle, D.; Gay, P.; Jousset, J.; Michel, B.; Monteil, S.; Pallin, D.; Pascolo, J. M.; Perret, P.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Kraan, A. C.; Nilsson, B. S.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Brient, J.-C.; Machefert, F.; Rougé, A.; Videau, H.; Ciulli, V.; Focardi, E.; Parrini, G.; Antonelli, A.; Antonelli, M.; Bencivenni, G.; Bossi, F.; Capon, G.; Cerutti, F.; Chiarella, V.; Laurelli, P.; Mannocchi, G.; Murtas, G. P.; Passalacqua, L.; Kennedy, J.; Lynch, J. G.; Negus, P.; O'Shea, V.; Thompson, A. S.; Wasserbaech, S.; Cavanaugh, R.; Dhamotharan, S.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Putzer, A.; Stenzel, H.; Tittel, K.; Wunsch, M.; Beuselinck, R.; Cameron, W.; Davies, G.; Dornan, P. J.; Girone, M.; Hill, R. D.; Marinelli, N.; Nowell, J.; Rutherford, S. A.; Sedgbeer, J. K.; Thompson, J. C.; White, R.; Ghete, V. M.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bouhova-Thacker, E.; Bowdery, C. K.; Clarke, D. P.; Ellis, G.; Finch, A. J.; Foster, F.; Hughes, G.; Jones, R. W. L.; Pearson, M. R.; Robertson, N. A.; Smizanska, M.; van der Aa, O.; Delaere, C.; Leibenguth, G.; Lemaitre, V.; Blumenschein, U.; Hölldorfer, F.; Jakobs, K.; Kayser, F.; Kleinknecht, K.; Müller, A.-S.; Renk, B.; Sander, H.-G.; Schmeling, S.; Wachsmuth, H.; Zeitnitz, C.; Ziegler, T.; Bonissent, A.; Coyle, P.; Curtil, C.; Ealet, A.; Fouchez, D.; Payre, P.; Tilquin, A.; Ragusa, F.; David, A.; Dietl, H.; Ganis, G.; Hüttmann, K.; Lütjens, G.; Männer, W.; Moser, H.-G.; Settles, R.; Villegas, M.; Wolf, G.; Boucrot, J.; Callot, O.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jacholkowska, A.; Serin, L.; Veillet, J.-J.; Azzurri, P.; Bagliesi, G.; Boccali, T.; Foà, L.; Giammanco, A.; Giassi, A.; Ligabue, F.; Messineo, A.; Palla, F.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Tenchini, R.; Venturi, A.; Verdini, P. G.; Awunor, O.; Blair, G. A.; Cowan, G.; Garcia-Bellido, A.; Green, M. G.; Jones, L. T.; Medcalf, T.; Misiejuk, A.; Strong, J. A.; Teixeira-Dias, P.; Clifft, R. W.; Edgecock, T. R.; Norton, P. R.; Tomalin, I. R.; Ward, J. J.; Bloch-Devaux, B.; Boumediene, D.; Colas, P.; Fabbro, B.; Lançon, E.; Lemaire, M.-C.; Locci, E.; Perez, P.; Rander, J.; Tuchming, B.; Vallage, B.; Litke, A. M.; Taylor, G.; Booth, C. N.; Cartwright, S.; Combley, F.; Hodgson, P. N.; Lehto, M.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Grupen, C.; Hess, J.; Ngac, A.; Prange, G.; Borean, C.; Giannini, G.; He, H.; Putz, J.; Rothberg, J.; Armstrong, S. R.; Berkelman, K.; Cranmer, K.; Ferguson, D. P. S.; Gao, Y.; González, S.; Hayes, O. J.; Hu, H.; Jin, S.; Kile, J.; McNamara, P. A.; Nielsen, J.; Pan, Y. B.; von Wimmersperg-Toeller, J. H.; Wiedenmann, W.; Wu, J.; Wu, S. L.; Wu, X.; Zobernig, G.; Dissertori, G.
2003-09-01
Exclusive production of /π and K meson pairs in two photon collisions is measured with ALEPH data collected between 1992 and 2000. Cross-sections are presented as a function of cosθ* and invariant mass, for cosθ*<0.6 and invariant masses between 2.0 and 6.0 GeV/c2 (2.25 and 4.0 GeV/c2) for pions (kaons). The shape of the distributions are found to be well described by QCD predictions but the data have a significantly higher normalization.
Exclusive production of pion and kaon meson pairs in two photon collisions at LEP
Heister, A; Antonelli, A; Antonelli, M; Armstrong, S R; Awunor, O; Azzurri, P; Badaud, F; Bagliesi, G; Barate, R; Barklow, Timothy L; Bencivenni, G; Berkelman, K; Beuselinck, R; Blair, G A; Bloch-Devaux, B; Blondel, A; Blumenschein, U; Boccali, T; Bonissent, A; Booth, C N; Borean, C; Bossi, F; Boucrot, J; Bouhova-Thacker, E; Boumediene, D E; Bowdery, C K; Brandt, S; Bravo, S; Brient, J C; Brunelière, R; Buchmüller, O L; Böhrer, A; Callot, O; Cameron, W; Capon, G; Cartwright, S; Casado, M P; Cattaneo, M; Cavanaugh, R J; Cerutti, F; Chiarella, V; Chmeissani, M; Ciulli, V; Clarke, D P; Clerbaux, B; Clifft, R W; Colaleo, A; Colas, P; Combley, F; Cowan, G; Coyle, P; Cranmer, K; Creanza, D; Crespo, J M; Curtil, C; David, A; Davier, M; Davies, G; De Bonis, I; De Filippis, N; De Palma, M; Delaere, C; Dessagne, S; Dhamotharan, S; Dietl, H; Dissertori, G; Dornan, P J; Drevermann, H; Duflot, L; Décamp, D; Ealet, A; Edgecock, T R; Ellis, G; Fabbro, B; Falvard, A; Fayolle, D; Ferguson, D P S; Fernández-Bosman, M; Fernández, E; Finch, A J; Focardi, E; Forty, R W; Foster, F; Fouchez, D; Foà, L; Frank, M; Ganis, G; Gao, Y; García-Bellido, A; Garrido, L; Gay, P; Geweniger, C; Ghete, V M; Giammanco, A; Giannini, G; Gianotti, F; Giassi, A; Girone, M; Girtler, P; González, S; Goy, C; Green, M G; Grivaz, J F; Grupen, C; Hanke, P; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Harvey, J; Hayes, O J; He, H; Hepp, V; Hess, J; Heusse, P; Hill, R D; Hodgson, P N; Hu, H; Huang, X; Hughes, G; Hutchcroft, D E; Hölldorfer, F; Hüttmann, K; Iaselli, G; Jacholkowska, A; Jakobs, K; Janot, P; Jin, S; Jones, L T; Jones, R W L; Jost, B; Jousset, J; Jézéquel, S; Kado, M; Kayser, F; Kennedy, J; Kile, J; Kleinknecht, K; Kluge, E E; Kneringer, E; Kraan, A C; Kuhn, D; Kyriakis, A; Lançon, E; Laurelli, P; Lees, J P; Lehto, M H; Leibenguth, G; Lemaire, M C; Lemaître, V; Ligabue, F; Lin, J; Litke, A M; Locci, E; Lynch, J G; Lütjens, G; Machefert, F P; Maggi, G; Maggi, M; Mannocchi, G; Marinelli, N; Markou, C; Martin, F; Martínez, M; Mato, P; McNamara, P A; Medcalf, T; Merle, E; Messineo, A; Michel, B; Minard, M N; Misiejuk, A; Monteil, S; Moser, H G; Moutoussi, A; Murtas, G P; Männer, W; Müller, A S; Negus, P; Ngac, A; Nielsen, J; Nilsson, B S; Norton, P R; Nowell, J; Nuzzo, S; O'Shea, V; Ouyang, Q; Pacheco, A; Palla, Fabrizio; Pallin, D; Pan, Y B; Parrini, G; Pascolo, J M; Passalacqua, L; Payre, P; Pearson, M R; Perret, P; Pietrzyk, B; Prange, G; Putzer, A; Pérez, P; Pütz, J; Ragusa, F; Rander, J; Ranieri, A; Ranjard, F; Raso, G; Renk, B; Robertson, N A; Rolandi, Luigi; Rothberg, J E; Rougé, A; Rudolph, G; Ruggieri, F; Ruiz, H; Rutherford, S A; Sander, H G; Sanguinetti, G; Schael, S; Schlatter, W D; Schmeling, S; Sciabà, A; Sedgbeer, J K; Selvaggi, G; Serin, L; Settles, Ronald; Sguazzoni, G; Silvestris, L; Simopoulou, Errietta; Smizanska, M; Spagnolo, R; Stenzel, H; Strong, J A; Taylor, G; Teixeira-Dias, P; Tempesta, P; Tenchini, A; Teubert, F; Thompson, A S; Thompson, J C; Thompson, L F; Tilquin, A; Tittel, K; Tomalin, I R; Tricomi, A; Trocmé, B; Tuchming, B; Valassi, Andrea; Vallage, B; Vayaki, Anna; Veillet, J J; Venturi, P; Verdini, P G; Videau, H L; Videau, I; Villegas, M; Von Wimmersperg-Töller, J H; Wachsmuth, H W; Wang, T; Ward, J J; Wasserbaech, S R; White, R; Wiedenmann, W; Wolf, G; Wu, J; Wu Sau Lan; Wu, X; Wunsch, M; Xie, Y; Xu, R; Xue, S; Zachariadou, K; Zeitnitz, C; Zhang, J; Zhang, L; Zhao, W; Ziegler, T; Zito, G; Zobernig, G; van der Aa, O
2003-01-01
Exclusive production of $\\pi$ and K meson pairs in two photon collisions is measured with ALEPH data collected between 1992 and 2000. Cross sections are presented as a function of \\cos\\theta^* and invariant mass, for |\\cos\\theta^* |< 0.6 and invariant masses between 2.0 and 6.0 \\mathrm{GeV}/c^2 (2.25 and 4.0 \\mathrm{GeV}/c^2) for pions (kaons). The shape of the distributions are found to be well described by QCD predictions but the data have a significantly higher normalisation.
Precise photoproduction of the charged top-pions at the LHC with forward detector acceptances
Sun, Hao; Yue, Chong-Xing
2014-04-01
We study the photoproduction of the charged top-pion predicted by the top triangle moose (TTM) model (a deconstructed version of the topcolor-assisted technicolor TC2 model) via the processes at the 14 TeV Large Hadron Collider (LHC) including next-to-leading order (NLO) QCD corrections. Our results show that the production cross sections and distributions are sensitive to the free parameters and . A typical QCD correction value is and this does not depend much on as well as the forward detector acceptances.
Precise photoproduction of the charged top-pions at the LHC with forward detector acceptances
Sun, Hao
2014-01-01
We study the photoproduction of the charged top-pion predicted by the top triangle moose ($TTM$) model (a deconstructed version of the topcolor-assisted technicolor $TC2$ model) via the processes $pp\\rightarrow p \\gamma p \\rightarrow \\pi^\\pm_t t +X$ at the 14 $TeV$ Large Hadron Collider ($LHC$) including next-to-leading order ($NLO$) $QCD$ corrections. Our results show that the production cross sections and distributions are sensitive to the free parameters $\\sin\\omega$ and $M_{\\pi_t}$. Typical $QCD$ correction value is $7\\% \\sim 11\\%$ and does not depend much on $\\sin\\omega$ as well as the forward detector acceptances.
Generalized vector form factors of the pion in a chiral quark model
Broniowski, Wojciech
2008-01-01
Generalized vector form factors of the pion, related to the moments of the generalized parton distribution functions, are evaluated in the Nambu--Jona-Lasinio model with the Pauli-Villars regularization. The lowest moments (the electromagnetic and the gravitational form factors) are compared to recent lattice data, with fair agreement. Predictions for higher-order moments are also made. Relevant features of the generalized form factors in the chiral quark models are highlighted and the role of the QCD evolution for the higher-order GFFs is stressed.
Measurement of the inclusive production of neutral pions and charged particles on the Z0 resonance
Adeva, B.; Adriani, O.; Aguilar-Benitez, M.; Akbari, H.; Alcaraz, J.; Aloisio, A.; Alverson, G.; Alviggi, M. G.; An, Q.; Anderhub, H.; Anderson, A. L.; Andreev, V. P.; Angelov, T.; Antonov, L.; Antreasyan, D.; Arce, P.; Arefiev, A.; Azemoon, T.; Aziz, T.; Baba, P. V. K. S.; Bagnaia, P.; Bakken, J. A.; Baksay, L.; Ball, R. C.; Banerjee, S.; Bao, J.; Barone, L.; Bay, A.; Becker, U.; Behrens, J.; Beingessner, S.; Bencze, Gy. L.; Berdugo, J.; Berges, P.; Bertucci, B.; Betev, B. L.; Biland, A.; Bizzarri, R.; Blaising, J. J.; Blömeke, P.; Blumenfeld, B.; Bobbink, G. J.; Bocciolini, M.; Bock, R.; Böhm, A.; Borgia, B.; Bourilkov, D.; Bourquin, M.; Boutigny, D.; Bouwens, B.; Branson, J. G.; Brock, I. C.; Bruyant, F.; Buisson, C.; Bujak, A.; Burger, J. D.; Burq, J. P.; Busenitz, J.; Cai, X. D.; Capell, M.; Carbonara, F.; Cardenal, P.; Carminati, F.; Cartacci, A. M.; Cerrada, M.; Cesaroni, F.; Chang, Y. H.; Chaturvedi, U. K.; Chemarin, M.; Chen, A.; Chen, C.; Chen, G. M.; Chen, H. F.; Chen, H. S.; Chen, M.; Chen, M. L.; Chen, W. Y.; Chiefari, G.; Chien, C. Y.; Chollet, F.; Civinini, C.; Clare, I.; Clare, R.; Cohn, H. O.; Coignet, G.; Colino, N.; Commichau, V.; Conforto, G.; Contin, A.; Crijns, F.; Cui, X. Y.; Dai, T. S.; D'Alessandro, R.; de Asmundis, R.; Degré, A.; Deiters, K.; Dénes, E.; Denes, P.; Denotaristefani, F.; Dhina, M.; Dibitonto, D.; Diemoz, M.; Diez-Hedo, F.; Dimitrov, H. R.; Dionisi, C.; Diviá, R.; Dova, M. T.; Drago, E.; Driever, T.; Duchesneau, D.; Duinker, P.; Duran, I.; El Mamouni, H.; Engler, A.; Eppling, F. J.; Erné, F. C.; Extermann, P.; Fabbretti, R.; Faber, G.; Fabre, M.; Falciano, S.; Fan, Q.; Fan, S. J.; Fackler, O.; Fay, J.; Fehlmann, J.; Ferguson, T.; Fernandez, G.; Ferroni, F.; Fesefeldt, H.; Field, J.; Filthaut, F.; Finocchiaro, G.; Fisher, P. H.; Forconi, G.; Foreman, T.; Freudenreich, K.; Friebel, W.; Fukushima, M.; Gailloud, M.; Galaktionov, Yu.; Gallo, E.; Ganguli, S. N.; Garcia-Abia, P.; Gau, S. S.; Gele, D.; Gentile, S.; Glaubman, M.; Goldfarb, S.; Gong, Z. F.; Gonzales, E.; Gordeev, A.; Göttlicher, P.; Goujon, D.; Gratta, G.; Grinnell, C.; Gruenewald, M.; Guanziroli, M.; Guo, J. K.; Gurtu, A.; Gustafson, H. R.; Gutay, L. J.; Haan, H.; Hasan, A.; Hauschildt, D.; He, C. F.; Hebbeker, T.; Hebert, M.; Herten, G.; Herten, U.; Hervé, A.; Hilgers, K.; Hofer, H.; Hoorani, H.; Hsu, L. S.; Hu, G.; Hu, G. Q.; Ille, B.; Ilyas, M. M.; Innocente, V.; Isiksal, E.; Janssen, H.; Jin, B. N.; Jones, L. W.; Kasser, A.; Khan, R. A.; Kamyshkov, Yu.; Karyotakis, Y.; Kaur, M.; Khokhar, S.; Khoze, V.; Kienzle-Focacci, M. N.; Kinnison, W.; Kirkby, D.; Kittel, W.; Klimentov, A.; König, A. C.; Kornadt, O.; Koutsenko, V.; Krammer, R. W.; Kramer, T.; Krastev, V. R.; Krenz, W.; Krizmanic, J.; Kumar, K. S.; Kumar, V.; Kunin, A.; Lalieu, V.; Landi, G.; Lanske, D.; Lanzano, S.; Lebrun, P.; Lecomte, P.; Lecoq, P.; Le Coultre, P.; Lee, D.; Leedom, I.; Le Goff, J. M.; Leistam, L.; Leiste, R.; Lenti, M.; Leonardi, E.; Lettry, J.; Levchenko, P. M.; Leytens, X.; Li, C.; Li, H. T.; Li, J. F.; Li, L.; Li, P. J.; Li, Q.; Lli, X. G.; Liao, J. Y.; Lin, Z. Y.; Linde, F. L.; Lindemann, B.; Linnhofer, D.; Liu, R.; Liu, Y.; Lohmann, W.; Longo, E.; Lu, Y. S.; Lubbers, J. M.; Lübelsmeyer, K.; Luci, C.; Luckey, D.; Ludovici, L.; Lue, X.; Luminari, L.; Ma, W. G.; MacDermott, M.; Magahiz, R.; Maire, M.; Malhotra, P. K.; Malik, R.; Malinin, A.; Manña, C.; Mao, D. N.; Mao, Y. F.; Maolinbay, M.; Marchesini, P.; Marchionni, A.; Martin, B.; Martin, J. P.; Martinez-Laso, L.; Marzano, F.; Massaro, G. G. G.; Matsuda, T.; Mazumdar, K.; McBride, P.; McMahon, T.; McNally, D.; Meinholz, Th.; Merk, M.; Merola, L.; Meschini, M.; Metzger, W. J.; Mi, Y.; Mills, G. B.; Mir, Y.; Mirabelli, G.; Mnich, J.; Möller, M.; Monteleoni, B.; Morand, G.; Morand, R.; Morganti, S.; Moulai, N. E.; Mount, R.; Müller, S.; Nagy, E.; Napolitano, M.; Newman, H.; Neyer, C.; Niaz, M. A.; Niessen, L.; Nowak, H.; Pandoulas, D.; Plasil, F.; Passaleva, G.; Paternoster, G.; Patricelli, S.; Pei, Y. J.; Perret-Gallix, D.; Perrier, J.; Pevsner, A.; Pieri, M.; Piroué, P. A.; Plyaskin, V.; Pohl, M.; Pojidaev, V.; Produit, N.; Qian, J. M.; Qureshi, K. N.; Raghavan, R.; Rahal-Callot, G.; Razis, P.; Read, K.; Ren, D.; Ren, Z.; Reucroft, S.; Ricker, A.; Riemann, S.; Rind, O.; Rippich, C.; Rizvi, H. A.; Roe, B. P.; Röhner, M.; Röhner, S.; Roeser, U.; Romero, L.; Rose, J.; Rosier-Lees, S.; Rosmalen, R.; Rosselet, Ph.; Rubbia, A.; Rubio, J. A.; Rubio, M.; Ruckstuhl, W.; Rykaczewski, H.; Sachwitz, M.; Salicio, J.; Sanders, G.; Sarakinos, M. S.; Sartorelli, G.; Sauvage, G.; Savin, A.; Schegelsky, V.; Schmiemann, K.; Schmitz, D.; Schmitz, P.; Schneegans, M.; Schopper, H.; Schotanus, D. J.; Shotkin, S.; Schreiber, H. J.; Schulte, R.; Schulte, S.; Schultze, K.; Schütte, J.; Schwenke, J.
1991-04-01
We present a study of the inclusive production of neutral pions and charged particles from 112 000 hadronic Z0 decays. The measured inclusive momentum distributions can be reproduced by parton shower Monte Carlo programs and also by an analytical QCD calculation. Comparing our results to e+e- data between √s = 9 and 91 GeV, we findfind that the evolution of the spectra with center of mass energy is consistent with the QCD predictions. Supported by the German Bundesministerium für Forschung und Technologie.
Antiproton--proton annihilation into pion pairs within effective meson theory
Wang, Ying; Tomasi-Gustafsson, Egle
2015-01-01
Antiproton--proton annihilation into light mesons is revisited in the few GeV energy domain, in view of a global description of the existing data. An effective meson model is developed, with mesonic and baryonic degrees od freedom in $s$, $t$, and $u$ channels. Regge factors are added to reproduce the proper energy behavior and the forward and backward peaked behavior. A comparison with existing data and predictions for angular distributions and energy dependence are done for charged and neutral pion pair production.
Isospin Dependence of Pion Absorption on Nucleon Pairs at Tπ=65 MeV
Moinester, M. A.; Gill, D. R.; Vincent, J.; Ashery, D.; Levenson, S.; Alster, J.; Altman, A.; Lichtenstadt, J.; Piasetzky, E.; Aniol, K. A.; Johnson, R. R.; Roser, H. W.; Tacik, R.; Gyles, W.; Barnett, B.; Sobie, R. J.; Gubler, H. P.
1984-04-01
Angular distributions of differential cross sections were measured for the first time for pion absorption on a T=1, S=0 nucleon pair and for absorption on a T=0, S=1 pair in the 3He nucleus. A large isospin dependence is observed in the differential cross sections. The ratio of cross sections σ(3He(π+,2p))σ(3He(π-,pn)) is 15.2+/-1.2. The results show evidence of an isoscalar component of the final state in the reaction 3He(π-,pn)n, which cannot be mediated by Δ resonance formation.
Thermal excitation of heavy nuclei with 5-15 GeV/c antiproton, proton and pion beams
Beaulieu, L; Hsi, W C; Lefort, T; Pienkowski, L; Korteling, R G; Wang, G; Back, B B; Bracken, D S; Breuer, H; Cornell, E A; Gimeno-Nogues, F; Ginger, D S; Gushue, S; Huang, M J; Laforest, R; Lynch, W G; Martin, E; Morley, K B; Ramakrishnan, E; Remsberg, L P; Rowland, D; Ruangma, A; Tsang, M B; Viola, V E; Winchester, E M; Xi, H; Yennello, S J
1999-01-01
Excitation-energy distributions have been derived from measurements of 5.0-14.6 GeV/c antiproton, proton and pion reactions with $^{197}$Au target nuclei, using the ISiS 4$\\pi$ detector array. The maximum probability for producing high excitation-energy events is found for the antiproton beam relative to other hadrons, $^3$He and $\\bar{p}$ beams from LEAR. For protons and pions, the excitation-energy distributions are nearly independent of hadron type and beam momentum above about 8 GeV/c. The excitation energy enhancement for $\\bar{p}$ beams and the saturation effect are qualitatively consistent with intranuclear cascade code predictions. For all systems studied, maximum cluster sizes are observed for residues with E*/A $\\sim$ 6 MeV.
Measurement of pion double charge exchange on carbon-13, carbon-14, magnesium-26, and iron-56
Energy Technology Data Exchange (ETDEWEB)
Seidl, P.A.
1985-02-01
Cross sections for the /sup 13,14/C,/sup 26/Mg,/sup 56/Fe(..pi../sup +/,..pi../sup -/)/sup 13,14/O,/sup 26/Si,/sup 56/Ni reactions were measured with the Energetic Pion Channel and Spectrometer at the Clinton P. Anderson Meson Physics Facility for 120 less than or equal to T/sub ..pi../ less than or equal to 292 MeV and 0 less than or equal to theta less than or equal to 50. The double isobaric analog states (DIAS) are of primary interest. In addition, cross sections for transitions to /sup 14/O(0/sup +/, 5.92 MeV), /sup 14/O(2/sup +/, 7.77 MeV), /sup 56/Ni(gs), /sup 13/O(gs), and /sup 13/O(4.21 MeV) are presented. The /sup 13/O(4.21 MeV) state is postulated to have J/sup ..pi../ = 1/2/sup -/. The data are compared to previously measured double-charge-exchange cross sections on other nuclei, and the systematics of double charge exchange on T greater than or equal to 1 target nuclei leading to the DIAS are studied. Near the ..delta../sub 33/ resonance, cross sections for the DIAS transitions are in disagreement with calculations in which the reaction is treated as sequential charge exchange through the free pion-nucleon amplitude, while for T/sub ..pi../ > 200 MeV the anomalous features of the 164 MeV data are not apparent. This is evidence for significant higher order contributions to the double-charge-exchange amplitude near the reasonable energy. Two theoretical approaches that include two nucleon processes are applied to the DIAS data. 64 references.
Pion-Nucleon Scattering in Kadyshevsky Formalism and Higher Spin Field Quantization
Wagenaar, J W
2009-01-01
This thesis contains two parts. The first part deals with pion-nucleon/meson-baryon scattering in the Kadyshevsky formalism. This formalism is introduced and discussed. Problems may arise when derivative couplings and/or higher spin fields are used, especially when compared to the results in the Feynman formalism: unwanted contact terms pop-up. These terms are cancelled using the Gross and Jackiw or Takahashi and Umezawa method. The final results in both formalisms are therefore equal, causal and covariant. Formal incorporation of pair suppression in the baryon exchange sector is achieved using a method based on the Takahashi and Umezawa method. For the resulting tree level amplitudes, we have shown, to our knowledge for the first time, that they are causal, covariant and n-independent. Moreover, the amplitudes are just a factor 1/2 of the usual Feynman expressions. The amplitudes contain only posititve energy initial and final states, although it should be mentioned that negative energy is present inside an ...
Nucleon Polarisabilities at and Beyond Physical Pion Masses
Griesshammer, Harald W; Phillips, Daniel R
2015-01-01
We examine the results of Chiral Effective Field Theory ($\\chi$EFT) for the scalar and spin-dipole polarisabilities of the proton and neutron for the physical pion mass and as a function of $m_\\pi$, thereby providing chiral extrapolations for lattice-QCD polarisability computations. We include both the leading and sub-leading effects of the nucleon's pion cloud, as well as the leading ones of the $\\Delta(1232)$ resonance and its pion cloud. The analytic results are complete at N${}^2$LO in the $\\delta$-counting for pion masses close to the physical value, and at leading order for pion masses similar to the Delta-nucleon mass splitting. In order to quantify the truncation error of our predictions and fits as 68% degree-of-belief confidence intervals, we use a Bayesian procedure recently adapted to EFT expansions. At the physical point, our predictions for the spin polarisabilities are, within respective errors, in good agreement with alternative extractions using experiments and dispersion-relation theory. At ...
Comparisons of pion simulations for the MOLLER experiment
Lunde, Dominic; Moller Collaboration
2016-09-01
The MOLLER experiment at Jefferson Lab will measure the parity-violating asymmetry in Møller scattering, the scattering of electrons from electrons. A precise measurement of this parity-violating asymmetry will allow us to determine the weak charge of the electron with a precision that improves over the E158 experiment at SLAC. The experiment will scatter electrons from a 11 GeV beam from atomic electrons in a liquid hydrogen target. The detected particles will include inelastically produced pions, which will be a background to our measurements. In this work we investigate the validity and accuracy of two available pion physics models in order to estimate the uncertainty in the size of the pion background in the simulation. Currently there are two methods of pion models implemented. The LUND model is based on the Pythia event generator and has been used with success in simulations for the SoLID experiment. The Wiser model is based on data from previous pion scattering experiments. Comparison of the rates, cross sections, particle momentum, scattering angles, and other parameters show that both models produce consistent results for the parameters that were studied in this work, within the range of energies and scattering angles of interest to the MOLLER experiment. The work was supported in part by the National Science Foundation under Grant Nos. PHY-1359364 and PHY-1405857.
Gauge invariance and the electromagnetic current of composite pions
Energy Technology Data Exchange (ETDEWEB)
Frank, M.R. [Hampton Univ., VA (United States). Dept. of Physics]|[Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Tandy, P.C. [Kent State Univ., OH (United States). Center for Nuclear Research
1993-03-24
The Global Color-symmetry Model of QCD is extended to deal with a background electromagnetic field, and the associated conserved current is identified for the finite size {bar q}q pion modes at tree level. A well-defined truncation issued that factorizes the bilocal pion field into a local field variable and a hadronic form factor having a ladder Bethe-Salpeter content. The associated pion charge form factor is formulated. These developments are used to provide an illustration of how an effective hadronic action containing form factors may be electromagnetically coupled in a gauge invariant way that is accountable to its field substructure. In particular, the Ward-Takahashi identity for the photon vertex appropriate to the localized pion fields is seen to contain the hadronic form factors. In this context, gauge invariance of the effective hadronic action also requires recognition of the fact that the free inverse propagator for the localized pion field gauge transforms due to the substructure field content that has been absorbed into it.
Binding energy of the $X(3872)$ at unphysical pion masses
Baru, V; Filin, A A; Gegelia, J; Nefediev, A V
2015-01-01
Chiral extrapolation of the $X(3872)$ binding energy is investigated using the modified Weinberg formulation of chiral effective field theory for the $D \\bar{D}^*$ scattering. Given its explicit renormalisability, this approach is particularly useful to explore the interplay of the long- and short-range $D \\bar{D}^*$ forces in the $X(3872)$ from studying the light-quark (pion) mass dependence of its binding energy. In particular, the parameter-free leading-order calculation shows that the $X$-pole disappears for unphysical large pion masses. On the other hand, without contradicting the naive dimensional analysis, the higher-order pion-mass-dependent contact interaction can change the slope of the binding energy at the physical point yielding the opposite scenario of a stronger bound $X$ at pion masses larger than its physical value. An important role of the pion dynamics and of the 3-body $D\\bar{D}\\pi$ effects for chiral extrapolations of the $X$-pole is emphasised. The results of the present study should be ...
Helenius, Ilkka; Paukkunen, Hannu
2014-01-01
In this talk, we present NLO pQCD predictions for inclusive pion and direct photon nuclear modifications in p+Pb collisions at mid- and forward rapidities at the LHC. In addition to the minimum bias predictions, we also address the centrality dependence with spatially dependent nuclear PDFs. To understand which regions of the nuclear momentum fraction $x_2$ these observables predominantly probe, we present also the underlying $x_2$ distributions at different rapidities. We are led to conclude that the isolated photons at forward rapidities are more sensitive to the small-$x_2$ dynamics than the inclusive pions.
Neutral Pion Double Helicity Asymmetry in Polarized Proton-Proton Collisions at √s=200 GeV at STAR
Leight, William
2012-03-01
One of the primary goals of the spin physics program at the STAR experiment is to constrain the polarized gluon distribution function δ(g)(x,Q^2) by measuring the double helicity asymmetry, ALL, of various final-state channels. Neutral pions are a potentially powerful final state because they are copiously produced in p+p collisions and have few backgrounds. STAR can identify neutral pions using its large-acceptance electromagnetic calorimeter, combined with a track veto from the STAR Time Projection Chamber. I will present progress towards measuring an ALL for neutral pions using ˜14 pb-1 of integrated luminosity taken during the 2009 200 GeV p+p run.