The pion pole term in electroproduction of off-mass-shell pions

International Nuclear Information System (INIS)

McKellar, B.H.; Ellis, R.G.

1983-01-01

The dependence of the invariant amplitudes for electroproduction of off-mass-shell pions on the pion Born term is investigated when current algebra Ward identities and PCAC are used to determine pion electroproduction invariant amplitudes. The authors show that an amplitude satisfying the Ward identities can be constructed starting from the usual Born terms which do not satisfy them and that this same amplitude will be obtained for a large class of input Born terms

Distortion of two-pion interferometry by multipion correlations

International Nuclear Information System (INIS)

Zhang, W.N.; Liu, Y.M.; Wang, S.; Liu, Q.J.; Jiang, J.; Keane, D.; Shao, Y.; Chu, S.Y.; Fung, S.Y.

1993-01-01

Multipion correlations arising from the symmetrization of the n-pion wave function affect the extracted information from two-pion correlation measurements. The influence of multipion correlations on a sample of like-pion pairs can be expressed as a multipion correlation factor, the distribution of which offers good sensitivity to the multipion correlation effect. Analyses of the multipion correlation factor for two Bevalac streamer chamber data samples of 2.1A GeV Ne+Pb and 1.8A GeV Ar+Pb collisions show that the multipion correlation effect in the former sample is greater than in the latter. This result mainly arises from the fact that the pion source for Ne projectiles is smaller than for Ar projectiles. The residual correlations in the reference sample are related to the multipion correlation factor in multipion events, which can be expressed as a residual correlation factor. The influence of multipion correlations on two-pion interferometry analyses arises from the ratio of the residual correlation factor to the multipion correlation factor

Some bounds on pion-scattering amplitudes and their applications

International Nuclear Information System (INIS)

Chung, B.K.; Vinh Mau, R.

1976-01-01

If one uses the method introduced by Meinam and further developed by Martin, together with unitarity crossing symmetry and analyticity, upper and lower bounds to the πdeg πged scattering amplitudes inside the Mandelstam triangle are obtained in terms of the scattering lengths. These bounds are used to set a lower bound to the renormalized pion coupling constant lambda. In terms of the D-wave scattering length a 2 , the results are a 0 greater than or equal to -23.18 square root a 2 + 129.07a 2 and -7.71 square root a 2 less than or equal to lambda less than or equal to 7.71 square root a 2 +2.5a 2 . For a 2 =7.10 -4 they yield a 2 greater than or equal to -0.52 and lambda less than or equal to 0.20 where the pion, mass is set equal to unity

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

Charge-odd and single-spin effects in two pion production in ep bar collisions

International Nuclear Information System (INIS)

Galynskij, M.V.; Kuraev, E.A.; Shajkhatdenov, B.G.; Ratcliffe, P.G.

2000-01-01

We consider two-photon and Bremsstrahlung mechanisms for the production of two charged pions in high-energy electron (proton) scattering off a transversely polarised proton. Interference between the relevant amplitudes generates a charge-odd contribution to the cross section for the process. In a kinematics with a jet moving along electron spin-independent part may be used for determination of phase differences for pion-pion scattering in the states with orbital momentum 0 or 2 and 1 whereas in a kinematics with a jet moving along proton spin-dependent part may be used to explain the experimental data for single-spin correlations in the production of negatively charged pions. We also discuss the backgrounds and estimate the accuracy of the results at less than 10% level. In addition simplified formulae derived for specific kinematics, with small total transverse pion momentum, are given

Exclusive electroproduction of two pions at HERA

CERN Document Server

Abramowicz, H.

2012-01-25

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...

Low energy pion-pion phase shifts from chiral perturbation theory

International Nuclear Information System (INIS)

Borges, J. Sa; Barbosa, J. Soares; Oguri, V.

1997-01-01

The low energy pion-pion S- and P- experimental phase-shifts are fitted with chiral perturbation theory (Ch PT) amplitude. The low energy pion-pion S- and P- experimental phase-shifts. The parameters l 1 and l 2 of the one loop corrected amplitude are fixed and the corresponding values of the scattering lengths are calculated. We propose that the present method is the best way to fix Ch P T parameters. The unitarization program of current algebra is also discussed. (author)

In-medium pion valence distributions in a light-front model

Energy Technology Data Exchange (ETDEWEB)

Melo, J.P.B.C. de, E-mail: joao.mello@cruzeirodosul.edu.br [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo (Brazil); Tsushima, K. [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo (Brazil); Ahmed, I. [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo (Brazil); National Center for Physics, Quaidi-i-Azam University Campus, Islamabad 45320 (Pakistan)

2017-03-10

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.

The pseudo-scalar form factor of the nucleon, the sigma-like term, and the L0+ amplitude for charged pion electro-production near threshold

International Nuclear Information System (INIS)

Cheoun, Myung Ki; Kim, K.S.

2007-01-01

The pseudo-scalar form factor, which represents the pseudo-scalar quark density distribution due to finite quark masses on the nucleon, is shown to manifest itself with the induced pseudo-scalar form factor in the L 0 + amplitude for the charged pion electro-production. Both form factors show their own peculiar momentum dependence. Under the approximation on which the Goldberger-Treiman relation holds, a sum of both form factors' contributions accounts for the t-channel contribution in the charged pion electro-production near threshold

Pion and kaon valence-quark parton quasidistributions

Science.gov (United States)

Xu, Shu-Sheng; Chang, Lei; Roberts, Craig D.; Zong, Hong-Shi

2018-05-01

Algebraic Ansätze for the Poincaré-covariant Bethe-Salpeter wave functions of the pion and kaon are used to calculate their light-front wave functions, parton distribution amplitudes, parton quasidistribution amplitudes, valence parton distribution functions, and parton quasidistribution functions (PqDFs). The light-front wave functions are broad, concave functions, and the scale of flavor-symmetry violation in the kaon is roughly 15%, being set by the ratio of emergent masses in the s - and u -quark sectors. Parton quasidistribution amplitudes computed with longitudinal momentum Pz=1.75 GeV provide a semiquantitatively accurate representation of the objective parton distribution amplitude, but even with Pz=3 GeV , they cannot provide information about this amplitude's end point behavior. On the valence-quark domain, similar outcomes characterize PqDFs. In this connection, however, the ratio of kaon-to-pion u -quark PqDFs is found to provide a good approximation to the true parton distribution function ratio on 0.4 ≲x ≲0.8 , suggesting that with existing resources computations of ratios of parton quasidistributions can yield results that support empirical comparison.

Pion production in nuclei

International Nuclear Information System (INIS)

Afnan, I.R.; Thomas, A.W.

1976-01-01

A method has been suggested for relating μ-capture in nuclei to pion absorption through partially conserved axial vector current hypothesis. The success of the method relies heavily on the knowledge of the pion absorption amplitude at a momentum transfer equal to the μ-meson mass. That is we need to know the pion absorption amplitude off the mass-shell. The simplest nucleus for which this suggestion can be examined is μ-capture in deuterium. The Koltum-Reitan model is used to determine the pion absorption amplitude off the mass shell. In particular the senstivity of this off-mass-shell extrapolution to details of the N-N interaction is studied. (author)

Precise tests for the unitarized pion photoproduction impulse amplitude in exclusive nuclear reactions

International Nuclear Information System (INIS)

Wittman, R.

1986-07-01

An impulse amplitude for pion photoproduction, suitable for the nuclear problem, is constructed with improved background dynamics and unitarity. The superior features of the amplitude are demonstrated at energies between threshold (E/sub γ/ = 150 MeV) and the Δ(1232) resonance energy (E/sub γ/ = 320 MeV) by discussing their effects on partial cross sections relevant to exclusive transitions in the 1p-shell. The specific reactions of 13 C(γ,π - ) 13 N/sub g.s./ and 14 N(γ,π + ) 14 C/sub g.s./ are discussed in light of these more general partial cross sections. The nuclear structure of the A = 14 system helps to enhance the effects considered. At or near resonance, very sizable (20 to 30%) effects arise both from the unitarity and from the refined treatment of the pionic final state interaction generated in the Δ-hole approach. Other examples of charged pion photoproduction reactions for 1p-shell nuclei are discussed briefly. Future theoretical improvements and experimental possibilities are suggested. 61 refs., 58 figs

Dispersion relation for hadronic light-by-light scattering: two-pion contributions

Energy Technology Data Exchange (ETDEWEB)

Colangelo, Gilberto [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, 3012 Bern (Switzerland); Hoferichter, Martin [Institute for Nuclear Theory, University of Washington, Seattle, WA 98195-1550 (United States); Kavli Institute for Theoretical Physics, University of California,Santa Barbara, CA 93106 (United States); Procura, Massimiliano [Theoretical Physics Department, CERN, Geneva (Switzerland); Stoffer, Peter [Helmholtz-Institut für Strahlen- und Kernphysik (Theory)and Bethe Center for Theoretical Physics, University of Bonn, 53115 Bonn (Germany); Department of Physics, University of California at San Diego, La Jolla, CA 92093 (United States)

2017-04-27

In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon (g−2){sub μ}, including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of γ{sup ∗}γ{sup ∗}→ππ. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, a{sub μ}{sup π-box}=−15.9(2)×10{sup −11}. As an application of the partial-wave formalism, we present a first calculation of ππ-rescattering effects in HLbL scattering, with γ{sup ∗}γ{sup ∗}→ππ helicity partial waves constructed dispersively using ππ phase shifts derived from the inverse-amplitude method. In this way, the isospin-0 part of our calculation can be interpreted as the contribution of the f{sub 0}(500) to HLbL scattering in (g−2){sub μ}. We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its S-wave rescattering corrections reads a{sub μ}{sup π-box}+a{sub μ,J=0}{sup ππ,π-pole} {sup LHC}=−24(1)×10{sup −11}.

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}, 32two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, vertical stroke F(M{sub {pi}}{sub {pi}}) vertical stroke, assuming that the studied mass range includes the contributions of the {rho}, {rho}{sup '} and {rho}'' vector-meson states. The masses and widths of the resonances were obtained and the Q{sup 2} dependence of the cross-section ratios {sigma}({rho}{sup '} {yields} {pi}{pi})/{sigma}({rho}) and {sigma}({rho}'' {yields} {pi}{pi})/{sigma}({rho}) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e{sup +}e{sup -} {yields} {pi}{sup +}{pi}{sup -}. (orig.)

Hard exclusive pion electroproduction at backward angles with CLAS

Science.gov (United States)

Park, K.; Guidal, M.; Gothe, R. W.; Pire, B.; Semenov-Tian-Shansky, K.; Laget, J.-M.; Adhikari, K. P.; Adhikari, S.; Akbar, Z.; Avakian, H.; Ball, J.; Balossino, I.; Baltzell, N. A.; Barion, L.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Cao, F. T.; Carman, D. S.; Celentano, A.; Charles, G.; Chetry, T.; Ciullo, G.; Clark, L.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Defurne, M.; Deur, A.; Djalali, C.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fersch, R.; Filippi, A.; Garçon, M.; Ghandilyan, Y.; Gilfoyle, G. P.; Girod, F. X.; Golovatch, E.; Griffioen, K. A.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Heddle, D.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jenkins, D.; Johnston, S.; Joo, K.; Kabir, M. L.; Keller, D.; Khachatryan, G.; Khachatryan, M.; Khandaker, M.; Kim, W.; Klein, F. J.; Kubarovsky, V.; Kuhn, S. E.; Lanza, L.; Livingston, K.; MacGregor, I. J. D.; Markov, N.; McKinnon, B.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Paolone, M.; Paremuzyan, R.; Pasyuk, E.; Phelps, W.; Pogorelko, O.; Poudel, J.; Price, J. W.; Prok, Y.; Protopopescu, D.; Ripani, M.; Rizzo, A.; Rossi, P.; Sabatié, F.; Salgado, C.; Schumacher, R. A.; Sharabian, Y.; Skorodumina, Iu.; Smith, G. D.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Strakovsky, I. I.; Strauch, S.; Taiuti, M.; Tan, J. A.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Wei, X.; Zachariou, N.; Zhang, J.

2018-05-01

We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, ep →e‧ nπ+, above the resonance region at backward pion center-of-mass angles. The φπ* -dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs). These non-perturbative objects are defined as matrix elements of three-quark-light-cone-operators and characterize partonic correlations with a particular emphasis on baryon charge distribution inside a nucleon.

Various models for pion probability distributions from heavy-ion collisions

International Nuclear Information System (INIS)

Mekjian, A.Z.; Mekjian, A.Z.; Schlei, B.R.; Strottman, D.; Schlei, B.R.

1998-01-01

Various models for pion multiplicity distributions produced in relativistic heavy ion collisions are discussed. The models include a relativistic hydrodynamic model, a thermodynamic description, an emitting source pion laser model, and a description which generates a negative binomial description. The approach developed can be used to discuss other cases which will be mentioned. The pion probability distributions for these various cases are compared. Comparison of the pion laser model and Bose-Einstein condensation in a laser trap and with the thermal model are made. The thermal model and hydrodynamic model are also used to illustrate why the number of pions never diverges and why the Bose-Einstein correction effects are relatively small. The pion emission strength η of a Poisson emitter and a critical density η c are connected in a thermal model by η/n c =e -m/T <1, and this fact reduces any Bose-Einstein correction effects in the number and number fluctuation of pions. Fluctuations can be much larger than Poisson in the pion laser model and for a negative binomial description. The clan representation of the negative binomial distribution due to Van Hove and Giovannini is discussed using the present description. Applications to CERN/NA44 and CERN/NA49 data are discussed in terms of the relativistic hydrodynamic model. copyright 1998 The American Physical Society

Elastic I=3 /2 p -wave nucleon-pion scattering amplitude and the Δ (1232) resonance from Nf=2+1 lattice QCD

DEFF Research Database (Denmark)

Andersen, Christian Walther; Bulava, John; Hörz, Ben

2018-01-01

We present the first direct determination of meson-baryon resonance parameters from a scattering amplitude calculated using lattice QCD. In particular, we calculate the elastic I=3/2, p-wave nucleon-pion amplitude on a single ensemble of Nf=2+1 Wilson-clover fermions with mπ=280 MeV and mK=460 Me......V. At these quark masses, the Δ(1232) resonance pole is found close to the N-π threshold and a Breit-Wigner fit to the amplitude gives gΔNπBW=19.0(4.7) in agreement with phenomenological determinations.......We present the first direct determination of meson-baryon resonance parameters from a scattering amplitude calculated using lattice QCD. In particular, we calculate the elastic I=3/2, p-wave nucleon-pion amplitude on a single ensemble of Nf=2+1 Wilson-clover fermions with mπ=280 MeV and mK=460 Me...

One, two and three pion production in pd collisions at 19 GeV/c

International Nuclear Information System (INIS)

Bakken, V.; Jacobsen, T.; Olsson, J.E.; Johansson, H.; Lundborg, P.; Sellden, B.; Maekelae, J.; Pimiae, H.; Sundell, E.

1976-04-01

Cross sections for coherent and non-coherent production of one, two and three pions in pd reactions at 19 GeV/c are presented. The mass distribution of the two pion non-coherent channels are studied. Strong single Δ(1236) and also some double Δ production are observed. Clear evidence for rho production is seen. (Auth.)

Exclusive production of pion pairs in γ*γ collisions at Large Q2

International Nuclear Information System (INIS)

Diehl, M.

2000-01-01

The authors perform a QCD analysis of the exclusive production of two mesons in γ*γ collisions in the kinematical domain of large photon virtuality Q and small hadronic invariant mass W. This reaction is dominated by a scale invariant mechanism which factorizes into a perturbative subprocess, γ*γ -> q anti q or γ*γ -> gg, and a generalized two-meson distribution amplitude. The authors develop in detail the phenomenology of this process at e + e - colliders. Using a simple model for the two-pion distribution amplitude, based on its general properties, the authors estimate the cross section for the kinematics accessible at BABAR, BELLE, CLEO and LEP

Dynamical pion production via parametric resonance from disoriented chiral condensates

Science.gov (United States)

Hiro-Oka, Hideaki; Minakata, Hisakazu

2000-04-01

We discuss a dynamical mechanism of pion production from disoriented chiral condensates. It leads to an explosive production of pions via the parametric resonance mechanism, which is similar to the reheating mechanism in inflationary cosmology. Classically it is related with the instability in the solutions of the Mathieu equation and we explore the quantum aspects of the mechanism. We show that nonlinearities and back reactions can be ignorable for a sufficiently long time under the small amplitude approximations of background σ oscillations, which may be appropriate for the late stage of a nonequilibrium phase transition. It allows us to obtain an explicit quantum state of the produced pions and σ, the squeezed state of BCS type. Single particle distributions and two pion correlation functions are computed within these approximations. The results obtained illuminate the characteristic features of multipion states produced through the parametric amplification mechanism. In particular, two pion correlations of various charge combinations contain back-to-back correlations which cannot be masked by the identical particle interference effect. We suggest that the parametric resonance mechanism might be a cause of the long lasting amplification of low-momentum modes in linear sigma model simulations.

On the use of distributions of stopping pions as an indicator of the spatial distribution of the high-LET dose in negative pion radiotherapy

International Nuclear Information System (INIS)

Brenner, D.J.

1991-01-01

A semi-empirical across the treatment volume of a therapeutic negative pion beam. Such beams deliver dose partially at high LET (through alphas and heavier particles produced both directly in pion stars and via intermediate star-produced neutrons), and partially at low LET (through scattering of pions, electrons and muons, as well as protons produced directly from pion stars and via intermediate neutrons). The problem is how to understand the spatial distribution of the high-LET dose, which is responsible for the potentially improved biological response in the treatment volume

Determination of amplitudes in neutral pion photoproduction and comparison with partial waves analysis in the energy range of 1.3 to 2.1 GeV

International Nuclear Information System (INIS)

Forozani, G.

2004-01-01

The magnitude of four independent amplitudes are obtained pion photoproduction in the energy range of 1300 to 2100 MeV incident photon. Different cross section and three polarization parameters are required for such amplitudes reconstruction at different pion scattering angles. Results of the direct amplitudes reconstruction have been compared with the solution of partial wave analysis SM95 and SM00K at all energies. This analysis indicates that we have a fair agreement between the present work and the results of partial wave analysis at many angles

Determination of amplitudes in neutral pion photoproduction and comparison with partial waves analysis in the energy range of 1.3 to 2.1 GeV

International Nuclear Information System (INIS)

Forozani, G.

2004-01-01

The magnitude of four independent amplitudes are obtained in neutral pion photoproduction in the energy range of 1300 to 2100 MeV incident photon. Differential gross section and three polarization parameters are required for such amplitudes reconstruction at different pion scattering angles. Results of the direct amplitudes reconstruction have been compared with the solution of partial wave analysis SM95 and SM00K at all energies. This analysis indicates that we have a fair agreement between the present work and the results of partial wave analysis at meny angles (Author)

Pion, pion-pion, and pion-nucleus interactions

CERN Document Server

Mukhin, K N; Tikhonov, V N

2002-01-01

This survey is devoted to describing the early studies of 1.1. Gurevich on pion physics that were performed by the photoemulsion method and the studies of the pion-pion interaction that were made by his colleagues on the basis of the hydrogen-bubble-chamber and the magnetic-spectrometer method (as well-as on the basis of the photoemulsion method). Two approaches-an extrapolation of experimental data from the physical region to the pion pole and a theoretical calculation based on the Roy integral equations-are used to deduce information about the pion-pion interaction. The first results obtained for pion-pion and pion-nucleus interactions in the experiments that are being currently performed in Brookhaven and at CERN ( pi pi interaction) and at TRIUMF (Canada) and in Brookhaven (pion-nucleus interaction) are presented, along with the existing theoretical concepts in these realms of physics. (80 refs).

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.

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.)

The two-nucleon system above pion threshold

International Nuclear Information System (INIS)

Poepping, H.; Sauer, P.U.; Zhang Xizhen

1987-01-01

A force model is presented for the description of the two-nucleon system below and above pion threshold and its coupled inelastic channels with one pion. It uses Δ-isobar and pion degrees of freedom in addition to the nucleonic one. The force model is based on a hamiltonian approach within the framework of noncovariant quantum mechanics. It extends the traditional approach with purely nucleonic potentials in isospin-triplet partial waves. It is constructed to remain valid up to 500 MeV c.m. energy. The characteristics of the force model is its mechanism for pion production and pion absorption which is mediated by the Δ-isobar. Even without any fit of phenomenological parameters the force model is able to account for the experimental data of elastic nucleon-nucleon scattering' of the inelastic reactions pp ↔ π + d and of elastic pion-deuteron scattering with satisfactory accuracy. No need for the introduction of dibaryon degrees of freedom has been found yet. The force model is a realistic one in the two-nucleon system. In many-nucleon systems it forms the unifying basis for a microscopic description of nuclear structure and nuclear reactions at low and intermediate energies. (orig.)

Virtual-pion and two-photon production in pp scattering

International Nuclear Information System (INIS)

Scholten, O.; Korchin, A.Yu.

2002-01-01

Two-photon production in pp scattering is proposed as a means of studying virtual-pion emission. Such a process is complementary to real-pion emission in pp scattering. The virtual-pion signal is embedded in a background of double-photon bremsstrahlung. We have developed a model to describe this background process and show that in certain parts of phase space the virtual-pion signal gives significant contributions. In addition, through interference with the two-photon bremsstrahlung background, one can determine the relative phase of the virtual-pion process

The ρ-meson light-cone distribution amplitudes from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Braun, Vladimir M.; Bruns, Peter C.; Collins, Sara [Institut für Theoretische Physik, Universität Regensburg,Universitätsstraße 31, 93040 Regensburg (Germany); Gracey, John A. [Theoretical Physics Division, Department of Mathematical Sciences, University of Liverpool, P.O. Box 147, Liverpool, L69 3BX (United Kingdom); Gruber, Michael; Göckeler, Meinulf; Hutzler, Fabian; Pérez-Rubio, Paula; Schäfer, Andreas; Söldner, Wolfgang [Institut für Theoretische Physik, Universität Regensburg,Universitätsstraße 31, 93040 Regensburg (Germany); Sternbeck, André [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena,Max-Wien-Platz 1, 07743 Jena (Germany); Wein, Philipp [Institut für Theoretische Physik, Universität Regensburg,Universitätsstraße 31, 93040 Regensburg (Germany)

2017-04-13

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{sub π}L=6.7 and pion masses down to m{sub π}=150 MeV. Bare lattice results are renormalized non-perturbatively using a variant of the RI{sup ′}-MOM scheme and converted to the (MS)-bar 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{sub ρ}{sup T}/f{sub ρ}=0.629(8) and the values of the second Gegenbauer moments a{sub 2}{sup ∥}=0.132(27) and a{sub 2}{sup ⊥}=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 expanding pion liquid and the pion spectra

International Nuclear Information System (INIS)

Ayala, A.

1999-01-01

We compute the pion inclusive momentum distribution in heavy-ion collisions for energies at the Alternating Gradient Synchrotron (AGS), assuming thermal equilibrium and accounting for density and expansion effects at freeze out. 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 transverse mass 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. (Author)

Exclusive production of pion pairs in {gamma}*{gamma} collisions at Large Q{sup 2}

Energy Technology Data Exchange (ETDEWEB)

Diehl, M.

2000-03-15

The authors perform a QCD analysis of the exclusive production of two mesons in {gamma}*{gamma} collisions in the kinematical domain of large photon virtuality Q and small hadronic invariant mass W. This reaction is dominated by a scale invariant mechanism which factorizes into a perturbative subprocess, {gamma}*{gamma} {r{underscore}arrow} q{anti q} or {gamma}*{gamma} {r{underscore}arrow} gg, and a generalized two-meson distribution amplitude. The authors develop in detail the phenomenology of this process at e{sup +}e{sup {minus}} colliders. Using a simple model for the two-pion distribution amplitude, based on its general properties, the authors estimate the cross section for the kinematics accessible at BABAR, BELLE, CLEO and LEP.

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); Collaboration: PANDA-Collaboration

2016-07-01

We address the feasibility of accessing proton to pion Transition Distribution Amplitudes with the future PANDA detector at the FAIR facility. 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 vertical stroke cosθ{sub π{sup 0}} vertical stroke > 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. The cross sections obtained with the simulations are used to test QCD factorization at the leading order by measuring scaling laws and fitting angular distributions.

A Nakanishi-based model illustrating the covariant extension of the pion GPD overlap representation and its ambiguities

Science.gov (United States)

Chouika, N.; Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.

2018-05-01

A systematic approach for the model building of Generalized Parton Distributions (GPDs), based on their overlap representation within the DGLAP kinematic region and a further covariant extension to the ERBL one, is applied to the valence-quark pion's case, using light-front wave functions inspired by the Nakanishi representation of the pion Bethe-Salpeter amplitudes (BSA). This simple but fruitful pion GPD model illustrates the general model building technique and, in addition, allows for the ambiguities related to the covariant extension, grounded on the Double Distribution (DD) representation, to be constrained by requiring a soft-pion theorem to be properly observed.

Disoriented chiral condensates and anomalous production of pions

International Nuclear Information System (INIS)

Martinis, M.; Mikuta-Martinis, V.; Crnugelj, J.

1999-01-01

The leading-particle effect and the factorization property of the scattering amplitude in the impact parameter space are used to study semiclassical production of pions in the central region. The mechanism is related to the isospin-uniform solution of the nonlinear σ-model coupled to quark degrees of freedom. The multipion exchange potential between two quarks is derived. It is shown that the soft chiral pion Bremsstrahlung also leads to anomalously large fluctuations in the ratio of neutral to charged pion.. We show that only direct production of pions in the form of an isoscalar coherent pulse without isovector pairs can lead to large neutral-charged fluctuations. (Authors)

Connected and disconnected contractions in pion-pion scattering

Science.gov (United States)

Acharya, Neramballi Ripunjay; Guo, Feng-Kun; Meißner, Ulf-G.; Seng, Chien-Yeah

2017-09-01

We show that the interplay of chiral effective field theory and lattice QCD can be used in the evaluation of so-called disconnected diagrams, which appear in the study of the isoscalar and isovector channels of pion-pion scattering and have long been a major challenge for the lattice community. By means of partially-quenched chiral perturbation theory, we distinguish and analyze the effects from different types of contraction diagrams to the pion-pion scattering amplitude, including its scattering lengths and the energy-dependence of its imaginary part. Our results may be used to test the current degree of accuracy of lattice calculation in the handling of disconnected diagrams, as well as to set criteria for the future improvement of relevant lattice computational techniques that may play a critical role in the study of other interesting QCD matrix elements.

Gluon distributions in nucleons and pions at a low resolution scale

International Nuclear Information System (INIS)

Christiansen, H.R.

2000-10-01

In this paper we study the gluon distribution functions in nucleons and pions at a low resolution Q 2 scale. This is an important issue since parton densities at low Q 2 have always been taken as an external input which is adjusted through DGLAP evolution to fit the experimental data at higher scales. Here, in the framework of a model recently developed, it is shown that the hypothetical cloud of neutral pions surrounding nucleons and pions appears to be responsible for the characteristic valence-like gluon distributions needed at the initial low scale. As an additional result, we get the remarkable prediction that neutral and charged ions have different intrinsic sea flavor contents. (author)

B→ππ form factors from light-cone sum rules with B-meson distribution amplitudes

Energy Technology Data Exchange (ETDEWEB)

Cheng, Shan; Khodjamirian, Alexander [Theoretische Physik 1, Naturwissenschaftlich-Technische Fakultät,Department Physik, Universität Siegen,Walter-Flex-Strasse 3, 57068 Siegen (Germany); Virto, Javier [Albert Einstein Center for Fundamental Physics,Institute for Theoretical Physics, University of Bern,Sidlerstrasse 5, CH-3012 Bern (Switzerland)

2017-05-30

We study B→ππ form factors using QCD light-cone sum rules with B-meson distribution amplitudes. These form factors describe the semileptonic decay B→ππℓν̄{sub ℓ}, and constitute an essential input in B→ππℓ{sup +}ℓ{sup −} and B→πππ decays. We employ the correlation functions where a dipion isospin-one state is interpolated by the vector light-quark current. We obtain sum rules where convolutions of the P-wave B̄{sup 0}→π{sup +}π{sup 0} form factors with the timelike pion vector form factor are related to universal B-meson distribution amplitudes. These sum rules are valid in the kinematic regime where the dipion state has a large energy and a low invariant mass, and reproduce analytically the known light-cone sum rules for B→ρ form factors in the limit of ρ-dominance and zero width, thus providing a systematics for so far unaccounted corrections to B→ρ transitions. Using data for the pion vector form factor, we estimate finite-width effects and the contribution of excited ρ-resonances to the B→ππ form factors. We find that these contributions amount up to ∼20% in the small dipion mass region where they can be effectively regarded as a nonresonant (P-wave) background to the B→ρ transition.

Light Meson Distribution Amplitudes

CERN Document Server

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.

Probing the 'nutcracker' by two-pion correlation

International Nuclear Information System (INIS)

Hirano, Tetsufumi; Morita, Kenji

2001-01-01

We investigate the 'nutcracker' phenomenon by studying two-pion correlation functions of non-central relativistic heavy-ion collisions. We apply the full (3+1)-dimensional hydro-dynamic model with first order phase transition. Based on numerical results which shows the 'nutcracked' freeze-out hypersurface, we calculate the two-pion correlation functions. In the case of snapshot hypersurfaces which clearly show the nut-shell structure, we find a interesting behavior at high relative momenta. We discuss the possibility of observing the phenomenon in heavy ion experiments. (author)

Pionic retardation effects in two-pion-exchange three-nucleon forces

International Nuclear Information System (INIS)

Coon, S.A.; Friar, J.L.

1986-01-01

Those two-pion-exchange three-nucleon forces which arise from nuclear processes that involve only pions and nucleons are calculated. Among the processes which contribute are pion seagulls (e.g., nucleon-antinucleon pair terms) and overlapping, retarded pion exchanges. The resulting potential is shown to be a (v/c) 2 relativistic correction, and satisfies nontrivial constraints from special relativity. The relativistic ambiguities found before in treatments of relativistic corrections to the one-pion-exchange nuclear charge operator and two-body potential are also present in the three-nucleon potential. The resulting three-nucleon force differs from the original Tucson-Melbourne potential only in the presence of several new nonlocal terms, and in the specification of the choice of ambiguity parameters in the latter potential

Pionic retardation effects in two-pion-exchange three-nucleon forces

Science.gov (United States)

Coon, S. A.; Friar, J. L.

1986-09-01

Those two-pion-exchange three-nucleon forces which arise from nuclear processes that involve only pions and nucleons are calculated. Among the processes which contribute are pion seagulls (e.g., nucleon-antinucleon pair terms) and overlapping, retarded pion exchanges. The resulting potential is shown to be a (v/c)2 relativistic correction, and satisfies nontrivial constraints from special relativity. The relativistic ambiguities found before in treatments of relativistic corrections to the one-pion-exchange nuclear charge operator and two-body potential are also present in the three-nucleon potential. The resulting three-nucleon force differs from the original Tucson-Melbourne potential only in the presence of several new nonlocal terms, and in the specification of the choice of ambiguity parameters in the latter potential.

Pionic retardation effects in two-pion-exchange three-nucleon forces

Energy Technology Data Exchange (ETDEWEB)

Coon, S.A.; Friar, J.L.

1986-09-01

Those two-pion-exchange three-nucleon forces which arise from nuclear processes that involve only pions and nucleons are calculated. Among the processes which contribute are pion seagulls (e.g., nucleon-antinucleon pair terms) and overlapping, retarded pion exchanges. The resulting potential is shown to be a (v-italic/c-italic)/sup 2/ relativistic correction, and satisfies nontrivial constraints from special relativity. The relativistic ambiguities found before in treatments of relativistic corrections to the one-pion-exchange nuclear charge operator and two-body potential are also present in the three-nucleon potential. The resulting three-nucleon force differs from the original Tucson-Melbourne potential only in the presence of several new nonlocal terms, and in the specification of the choice of ambiguity parameters in the latter potential.

Conformal symmetry and pion form factor: Soft and hard contributions

International Nuclear Information System (INIS)

Choi, Ho-Meoyng; Ji, Chueng-Ryong

2006-01-01

We discuss a constraint of conformal symmetry in the analysis of the pion form factor. The usual power-law behavior of the form factor obtained in the perturbative QCD analysis can also be attained by taking negligible quark masses in the nonperturbative quark model analysis, confirming the recent AdS/CFT correspondence. We analyze the transition from soft to hard contributions in the pion form factor considering a momentum-dependent dynamical quark mass from an appreciable constituent quark mass at low momentum region to a negligible current quark mass at high momentum region. We find a correlation between the shape of nonperturbative quark distribution amplitude and the amount of soft and hard contributions to the pion form factor

Forward pion-nucleon charge exchange reaction and Regge constraints

International Nuclear Information System (INIS)

Huang Fei; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meibner, U.-G.

2009-01-01

We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude. (authors)

Roy-Steiner-equation analysis of pion-nucleon scattering

Science.gov (United States)

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.

Interplay between one-body and two-body dynamics in the subthreshold pion production at intermediate energies

International Nuclear Information System (INIS)

Cassing, W.

1984-12-01

The role of the time-dependent mean field in subthreshold pion production by first chance nucleon-nucleon collisions is studied for heavy-ion reactions at intermediate energies in a finite two-center shell model. It is found that the energy distribution of the nucleons for overlapping ions can roughly be approximated by shifted groundstate momentum distributions using a quasi-free dispersion relation. The absolute cross sections for the production of neutron pions can be reproduced from 35 MeV/u to 150 MeV/u. (orig.)

Diphoton generalized distribution amplitudes

International Nuclear Information System (INIS)

El Beiyad, M.; Pire, B.; Szymanowski, L.; Wallon, S.

2008-01-01

We calculate the leading order diphoton generalized distribution amplitudes by calculating the amplitude of the process γ*γ→γγ in the low energy and high photon virtuality region at the Born order and in the leading logarithmic approximation. As in the case of the anomalous photon structure functions, the γγ generalized distribution amplitudes exhibit a characteristic lnQ 2 behavior and obey inhomogeneous QCD evolution equations.

Theory of the low-energy pion-nucleon interaction

International Nuclear Information System (INIS)

Banerjee, M.K.; Cammarata, J.B.

1978-01-01

A once-subtracted form of the Low equation for the pion-nucleon scattering amplitude is derived, with partial conservation of axial-vector current used to define the amplitude when one pion is off the mass shell. The static approximation is not made and both the seagull terms and the antinucleon contribution (z graphs) are retained. The theory is applied to calculate the S-wave amplitudes in the elastic scattering region. Good agreement is found with the phase shift fits to the data when we use vertical-barg/sub π/(4M 2 ) vertical-bar = 11.69 and 25.5 MeV for the πN sigma commutator. The implications of this work for the analysis of low-energy elastic scattering of pions form nuclei are discussed. In particular, we point out how this work establishes the presence of a Laplacian term in the pion-nucleus optical potential with a magnitude that is fixed from the value of the sigma commutator

Pion observables and QCD

International Nuclear Information System (INIS)

Roberts, C.D.

1995-01-01

Herein the application of the DSE approach to the calculation of pion observables is described using: the π-π scattering lengths (a 0 0 , a 2 0 , a 1 1 , a 0 2 , a 2 2 ) and associated partial wave amplitudes; the π 0 → γγ decay width; and the charged pion form factor, F π (q 2 ), as illustrative examples. Since this approach provides a straightforward, microscopic description of dynamical chiral symmetry breaking (DχSB) and confinement, the calculation of pion observables is a simple and elegant illustrative example of its power and efficacy. (orig.)

Experimental access to Transition Distribution Amplitudes with the P¯ANDA experiment at FAIR

Science.gov (United States)

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

Photoproduction of pions on nuclear in chiral bag model with account of motion effects of recoil nucleon

International Nuclear Information System (INIS)

Dorokhov, A.E.; Kanokov, Z.; Musakhanov, M.M.; Rakhimov, A.M.

1989-01-01

Pion production on a nucleon is studied in the chiral bag model (CBM). A CBM version is investigated in which the pions get into the bag and interact with quarks in a pseudovector way in the entire volume. Charged pion photoproduction amplitudes are found taking into account the recoil nucleon motion effects. Angular and energy distributions of charged pions, polarization of the recoil nucleon, multipoles are calculated. The recoil effects are shon to give an additional contribution to the static approximation of order of 10-20%. At bag radius value R=1 in the calculations are consistent with the experimental data

Inelastic pion scattering by 13C at low energies

International Nuclear Information System (INIS)

Mitchell, J.H.

1987-03-01

Angular distributions for inelastically scattered pions were obtained for several states in 13 C at an incident energy of 65 MeV. The data include results from both π + and π - measurements. In addition, π - measurements were made at T/sub π/ = 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 + 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

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.

The pion form factor from first principles

International Nuclear Information System (INIS)

Heide, J. van der

2004-01-01

We calculate the electromagnetic form factor of the pion in quenched lattice QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the O(a) improved current. We calculate form factor for pion masses down to mπ = 380 MeV. We compare the mean square radius for the pion extracted from our form factors to the value obtained from the 'Bethe Salpeter amplitude'. Using (quenched) chiral perturbation theory, we extrapolate our results towards the physical pion mass

Neutrino production of single pions: Dipole description

International Nuclear Information System (INIS)

Kopeliovich, B. Z.; Schmidt, Ivan; Siddikov, M.

2011-01-01

The light-cone distribution amplitudes for the axial current are derived within the instanton vacuum model, which incorporates nonperturbative effects including spontaneous chiral symmetry breaking. This allows one to extend applicability of the dipole approach, usually used in the perturbative domain, down to Q 2 →0, where the partially conserved axial current imposes a relation between the neutrino-production cross section and the one induced by pions. A dramatic breakdown of the Adler relation for diffractive neutrino production of pions, caused by absorptive corrections, was revealed recently by Kopeliovich et al.. Indeed, comparing with the cross section predicted by the dipole phenomenology at Q 2 →0 on a proton target we confirmed the sizable deviation from the value given by the Adler relation, as was estimated by Kopeliovich et al. within a simplified two-channel model. The dipole approach also confirms that in the black-disk limit, where the absorptive corrections maximize, the diffractive cross section ceases, on the contrary to the expectation based on the partially conserved axial current.

Corrections to the one-pion exchange amplitudes for the reaction np→pΔsub(33)sup(deg)

International Nuclear Information System (INIS)

Ferraz De Camargo, A.; Laville, J.L.

1978-01-01

A simple modified one-pion exchange model is applied to the analysis of the reaction np→pΔsub(33)sup(deg) from 1.39 to 1.90GeV/c. It is shown that important corrections to the evasive amplitudes can account for the turnover observed in the differential cross-section and rather good fits are obtained. Such corrections do not agree with the prescription known as ''poor man's absorption''. The results for the density matrix elements are briefly discussed

Pion photoproduction in the Skyrme model and low-energy theorem

International Nuclear Information System (INIS)

Saito, Sakae; Takeuchi, Fuminaka; Uehara, Masayuki

1993-01-01

We investigate pion photoproduction on the nucleon in the Skyrme model. We employ the formulation, which was recently developed by Hayashi et al., that the full pion field is treated as an interpolating field between asymptotic in and out fields. It is shown that the amplitude of the pion photoproduction is correctly given by the direct and the crossed baryon-pole terms, and the equal-time commutator terms between the axial-vector current and the electromagnetic current and between the pion field and the latter. We show that the lowest-order Kroll-Ruderman and the pion pole terms are reproduced, and that the seagull terms inherent to the Skyrme model are present. Further, the threshold behavior of the amplitude is discussed. (orig.)

Low-energy photo- and electroproduction for physical pions

International Nuclear Information System (INIS)

MacMullen, J.T.

1979-02-01

The Ward identities of current algebra are combined with gauge invariance constraints, on-shell PCAC and the Bjorken limit to obtain the low-energy expressions of the pion photo- and electroproduction invariant amplitudes for physical pions

Pion-pair production by two photons

International Nuclear Information System (INIS)

Terazawa, Hidezumi.

1994-07-01

The cross section for pion-pair production by two photons is calculated approximately by using the low energy theorem previously derived from partially-conserved-axial-vector-current hypothesis and current algebra, and found to agree very well with the experimental data recently obtained by the Mark II, TPC/Two-Gamma and CLEO Collaborations. (author)

Distribution amplitudes of vector mesons

Energy Technology Data Exchange (ETDEWEB)

Braun, V.M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Broemmel, D. [Deutsches Elektronen-Synchrotron, Hamburg (Germany); Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

2007-11-15

Results are presented for the lowest moment of the distribution amplitude for the K{sup *} vector meson. Both longitudinal and transverse moments are investigated. We use two flavours of O(a) improved Wilson fermions, together with a non-perturbative renormalisation of the matrix element. (orig.)

Invariant mass dependence of two-pion inclusive correlation functions

International Nuclear Information System (INIS)

Berger, E.L.; Singer, R.; Thomas, G.H.; Kafka, T.

1976-06-01

High energy two-particle inclusive correlations are studied as a function of the invariant mass M of the pair. Using data from 205 GeV/c pp interactions, one compares the correlation functions C(M) for (+-) and (--) pairs of produced pions. Strong positive correlations are observed in both distributions in the form of a broad threshold enhancement at small M. The decrease of C(M) as M increases is interpreted in the Mueller-Regge framework. From the M dependence of C +- one extracts an effective trajectory intercept of roughly α(0) approximately equal to 0.5 +- 0.1, consistent with the (rho,f) pair. For the exotic (--) system, one finds a low intercept, α(0) approximately equal to -0.5. A rho resonance signal is observed above background in C +- (M). Near threshold, effects suggestive of Bose symmetry are seen but are not conclusive. In an exclusive picture, one relates most of the correlation in the threshold region to resonances involving three or more pions. One also examines the joint correlations in M and the azimuthal angle phi

Analysis of the pion-kaon sigma term and related topics

International Nuclear Information System (INIS)

Frink, M.; Kubis, B.; Meissner, U.G.

2002-01-01

We calculate the one-loop contributions to the difference Δ πK between the isoscalar on-shell pion-kaon scattering amplitude at the Cheng-Dashen point and the scalar form factor Γ K (2M 2 π ) 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. (orig.)

Analysis of the pion-kaon sigma term and related topics

Energy Technology Data Exchange (ETDEWEB)

Frink, M.; Kubis, B.; Meissner, U.G. [Forschungszentrum Juelich, Institut fuer Kernphysik (Theorie), Juelich (Germany)

2002-09-01

We calculate the one-loop contributions to the difference {delta}{sub {pi}}{sub K} between the isoscalar on-shell pion-kaon scattering amplitude at the Cheng-Dashen point and the scalar form factor {gamma}{sub K} (2M{sup 2}{sub {pi}}) 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. (orig.)

Exclusive channels in semi-inclusive production of pions and kaons

International Nuclear Information System (INIS)

Markus Diehl; Wolfgang Kugler; Andreas Schaefer; Christian Weiss

2005-01-01

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

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.

Low-energy pion-nucleon scattering

International Nuclear Information System (INIS)

Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

1998-01-01

An analysis of low-energy charged pion-nucleon data from recent π ± p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f 2 =0.0756±0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P 31 and P 13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided. copyright 1998 The American Physical Society

Pion-nucleus scatter and the Pauli principle

International Nuclear Information System (INIS)

Dover, C.B.; Lemmer, R.H.

1976-01-01

A density expansion of the pion self-energy for pions in nuclear matter is reexamined. It is shown that a single hole-line expansion of the self-energy (i) is equivalent to using a strongly quenched πN scattering amplitude in the medium, and (ii) results in an inconsistent treatment of the virtual pions necessarily present in a field-theoretic description of the problem. Exchange of intermediate pions gives rise to nucleon-nucleon, as well as pion-nucleon scattering diagrams that both contribute to the pion self-energy in an essential way. The nucleon-nucleon scattering proceeds, for instance, via a one-pion-exchange potential that is, however, highly nonstatic for energy transfers between nucleons close to the incident energy. Such interactions are singled out automatically for special treatment in a field-theory approach to the problem, and should not be introduced in an ad hoc manner as part of an empirical NN interaction in nuclear matter. We evaluate the coherent and charge exchange contributions to the pion-nucleus optical potential, proportional to the total density and the neutron-proton density difference, respectively. The Pauli principle is found to provide a small correction to the coherent part, both in the hole-line and density expansion formalisms. However, the charge exchange part of the potential is almost completely damped at low energies in the hole-line expansion, while the inclusion of backward-going graphs (random-phase-approximation-type correlations) restores it to its value based on free space πN charge exchange amplitudes (i.e., no net Pauli effect)

Pion-pair formation and the pion dispersion relation in a hot pion gas

Energy Technology Data Exchange (ETDEWEB)

Chanfay, G. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire; Alm, T. [Rostock Univ. (Germany); Schuck, P. [Grenoble-1 Univ., 38 (France). Inst. des Sciences Nucleaires; Welke, G. [Wayne State Univ., Detroit, MI (United States). Dept. of Physics and Astronomy

1996-09-01

The possibility of pion-pair formation in a hot pion gas, based on the bosonic gap equation, is pointed out and discussed in detail. The critical temperature for condensation of pion pairs (Evans-Rashind transition) is determined as a function of the pion density. As for fermions, this phase transition is signaled by the appearance of a pole in the two-particle propagator. In Bose systems there exists a second, lower critical temperature, associated with the appearance of the single-particle condensate. Between the two critical temperatures the pion dispersion relation changes from the usual quasiparticle dispersion to a Bogoliubov-like dispersion relation at low momenta. This generalizes the non-relativistic results for an attractive Bose gas by Evans et al. Possible consequences for the inclusive pion spectra measured in heavy-ion collisions at ultra-relativistic energies are discussed. 21 refs.

Can pions created in high-energy heavy-ion collisions produce a Centauro-type effect?

International Nuclear Information System (INIS)

Martinis, M.; Mikuta-Martinis, V.; Crnugelj, J.

1995-01-01

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. We show that the Centauro-type effect is strongly suppressed if a large number of pions are produced in isovector pairs. Our conclusion is supported through the calculation of two pion correlation parameters, f 2 0- and f 2 00 , as well as f 2, n - 0 and the average number of neutral pions (left-angle n 0 right-angle n- ) a a function of negative pions (n - ) produced

Multi-pion production

International Nuclear Information System (INIS)

Beavis, D.; Fung, S.Y.; Gorn, W.; Keane, D.; Liu, Y.M.; Poe, R.T.; VanDalen, G.; Vient, M.

1984-01-01

Preliminary analysis of pion production in 1.2 GeV/nucleon Kr-RbBr collisions is presented. The negative pion multiplicity is consistent with a convolution of Poisson distributions and a freeze-out density between 1/3 and 1/2 normal nuclear density is extracted. Global negative pion kinematic variables are used to search for possible structure in the multi-pion emission. No evidence for structured emission or conservation constraints is found. Pion interferometry analysis gives a source radius of 5.4 +- 1.2 Fermi and a freeze-out density of .3 +- .2 times normal nuclear density. 10 refs., 5 figs

Forward amplitude in pion deuteron

International Nuclear Information System (INIS)

Ferreira, E.M.; Munguia, G.A.P.; Rosa, L.P.; Thome, Z.D.

1979-06-01

The data on total cross section for πd scattering is analysed in terms of a single scattering calculation with Fermi motion dependence, in order to obtain a criterion to fix the value of the energy entering the two body meson nucleon amplitude. It is found that the prescription derived from the non-relativistic three body kinematics gives reasonable results. The introduction of a shift in the energy value, possibly representing nuclear binding effects, leads to a very good fitting of the data. The results are compared with those obtained in direct calculations of Faddeev equations and with the Brueckner model of fixed scatterers. (Author) [pt

Two-pion correlations in heavy ion collisions

International Nuclear Information System (INIS)

Zajc, W.A.

1982-08-01

An application of intensity interferometry to relativistic heavy ion collisions is reported. Specifically, the correlation between two like-charged pions is used to study the reactions Ar+KCl→2π/sup +-/+X and Ne+NaF→2π - +X. Source sizes are obtained that are consistent with a simple geometric interpretation. Lifetimes are less well determined but are indicative of a faster pion production process than predicted by Monte Carlo cascade calculations. There appears to be a substantial coherent component of the pion source, although measurement is complicated by the presence of final state interactions. Additionally, the generation of spectra of uncorrelated events is discussed. In particular, the influence of the correlation function on the background spectrum is analyzed, and a prescription for removal of this influence is given. A formulation to describe the statistical errors in the background is also presented. Finally, drawing from the available literature, a self-contained introduction to Bose-Einstein correlations and the Hanbury-Brown - Twiss effect is provided, with an emphasis on points of contact between classical and quantum mechanical descriptions

Perturbative renormalizability of chiral two-pion exchange in nucleon-nucleon scattering

International Nuclear Information System (INIS)

Pavon Valderrama, M.

2011-01-01

We study the perturbative renormalizability of chiral two-pion exchange for singlet and triplet channels within effective field theory, provided that the one-pion exchange piece of the interaction has been fully iterated. We determine the number of counterterms/subtractions needed to obtain finite results when the cutoff is removed, resulting in three counterterms for the singlet channel and six for the triplet. The results show that perturbative chiral two-pion exchange reproduce the data up to a center-of-mass momentum of k∼200-300 MeV in the singlet channel and k∼300-400 MeV in the triplet.

Pion-nucleon scattering: from chiral perturbation theory to Roy-Steiner equations

Science.gov (United States)

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.*

Pion transverse momentum dependent parton distributions in the Nambu and Jona-Lasinio model

Energy Technology Data Exchange (ETDEWEB)

Noguera, Santiago [Departament de Fisica Teòrica and IFIC, Universitat de València - CSIC,E-46100 Burjassot (Spain); Scopetta, Sergio [Dipartimento di Fisica e Geologia, Università degli Studi di Perugia,via A. Pascoli, I - 06123 Perugia (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, via A. Pascoli, I - 06123 Perugia (Italy)

2015-11-16

An explicit evaluation of the two pion transverse momentum dependent parton distributions at leading twist is presented, in the framework of the Nambu-Jona Lasinio model with Pauli-Villars regularization. The transverse momentum dependence of the obtained distributions is generated solely by the dynamics of the model. Using these results, the so called generalized Boer-Mulders shift is studied and compared with recent lattice data. The obtained agreement is very encouraging, in particular because no additional parameter has been introduced. A more conclusive comparison would require a precise knowledge of the QCD evolution of the transverse momentum dependent parton distributions under scrutiny.

Production of a pion in association with a high-Q2 dilepton pair in antiproton-proton annihilation at GSI-FAIR

International Nuclear Information System (INIS)

Lansberg, J. P.; Pire, B.; Szymanowski, L.

2007-01-01

We evaluate the cross section for pp→l + l - π 0 in the forward direction and for a large lepton pair invariant mass. In this kinematical region, the leading-twist amplitude factorizes into a short-distance matrix element, long-distance antiproton-distribution amplitudes, and proton to pion transition distribution amplitudes (TDAs). Using a modeling inspired from the chiral limit for these TDAs, we obtain a first estimate of this cross section, which demonstrates that this process can be measured at GSI-FAIR

Two-nucleon S10 amplitude zero in chiral effective field theory

Science.gov (United States)

Sánchez, M. Sánchez; Yang, C.-J.; Long, Bingwei; van Kolck, U.

2018-02-01

We present a new rearrangement of short-range interactions in the S10 nucleon-nucleon channel within chiral effective field theory. This is intended to address the slow convergence of Weinberg's scheme, which we attribute to its failure to reproduce the amplitude zero (scattering momentum ≃340 MeV) at leading order. After the power counting scheme is modified to accommodate the zero at leading order, it includes subleading corrections perturbatively in a way that is consistent with renormalization-group invariance. Systematic improvement is shown at next-to-leading order, and we obtain results that fit empirical phase shifts remarkably well all the way up to the pion-production threshold. An approach in which pions have been integrated out is included, which allows us to derive analytic results that also fit phenomenology surprisingly well.

Analysis of stationary power/amplitude distributions for multiple channels of sampled FBGs.

Science.gov (United States)

Xing, Ya; Zou, Xihua; Pan, Wei; Yan, Lianshan; Luo, Bin; Shao, Liyang

2015-08-10

Stationary power/amplitude distributions for multiple channels of the sampled fiber Bragg grating (SFBG) along the grating length are analyzed. Unlike a uniform FBG, the SFBG has multiple channels in the reflection spectrum, not a single channel. Thus, the stationary power/amplitude distributions for these multiple channels are analyzed by using two different theoretical models. In the first model, the SFBG is regarded as a set of grating sections and non-grating sections, which are alternately stacked. A step-like distribution is obtained for the corresponding power/amplitude of each channel along the grating length. While, in the second model, the SFBG is decomposed into multiple uniform "ghost" gratings, and a continuous distribution is obtained for each ghost grating (i.e., each channel). After a comparison, the distributions obtained in the two models are identical, and the equivalence between the two models is demonstrated. In addition, the impacts of the duty cycle on the power/amplitude distributions of multiple channels of SFBG are presented.

Determination of backward pion nucleon scattering amplitudes

International Nuclear Information System (INIS)

Pietarinen, E.

1978-04-01

Backward C(sup(+-))πN amplitudes are determined from πN→Nπ and NantiN→2π differential cross sections in such a way that they are consistent with the analyticity properties and information of the unphysical ππ→NantiN amplitudes. Combining the result with forward C(sup(+-)) amplitudes positive and negative parity resonances are extracted. An error analysis of the amplitudes is performed. (author)

Effect of two-pion exchange in nucleon-nucleon scattering in high partial waves

International Nuclear Information System (INIS)

Harun ar Rashid, A.M.; Chaudhury, T.K.

1983-01-01

The work of Brown and Durso (Phys. Lett. 35B, 120 (1971)) on the soft-pion determination of the intermediate range nucleon-nucleon interaction is extended by using the most general form of the ΔNπ interaction which involves an arbitrary parameter Z. It is shown that both the annihilation channel helicity amplitude fsub(+)sup((O))(t) as well as peripheral proton-proton scattering phase shifts seem to favour Z=1/2. (author)

Transverse-target single-spin azimuthal asymmetry in hard exclusive electroproduction of single pions at HERMES

International Nuclear Information System (INIS)

Hristova, I.

2007-12-01

We present the analysis of data taken in the years 2002-2004 with the 27.56 GeV positron beam of the HERA storage ring at DESY and the internal transversely polarised hydrogen fixed target of the HERMES experiment. Events with a scattered positron and a produced pion are selected. Exclusive production of single pions, e + p→e +' nπ + , is ensured by requiring the missing mass in the event to be equal to the mass of the neutron, which is not detected. The cross section for this process depends on the Bjorken scaling variable, the four-momentum transfer, and the transverse four-momentum transfer, whose average values for our sample are left angle x right angle =0.12, left angle Q 2 right angle =2.3 GeV 2 , left angle t' right angle =-0.18 GeV 2 , respectively, and two azimuthal angles: the angle φ between the scattering and production planes (their common line contains the virtual photon), and the angle φ S between the scattering plane and the target polarisation vector. The hard scattering is selected by requiring Q 2 >1 GeV 2 . The asymmetry, also called transverse-target single-spin azimuthal asymmetry, is defined as the ratio of the difference to the sum of the cross sections for positive and negative target polarisation. It is characterised by six azimuthal sine modulations, whose amplitudes can vary from -1 to 1. We measure the asymmetry from a sample of 2093 events with a signal-to-background ratio of 1: 1. At average kinematics, the values of the amplitudes are found to be small or consistent with zero, except for the amplitude A sinφ S UT,meas =0.38±0.06(stat) +0.12 -0.06 (syst). The amplitude of main interest for comparison with theory, A sin(φ-φ S ) UT,meas =0.09±0.05(stat) +0.10 -0.03 (syst), after correction for the background contribution becomes A sin(φ-φ S ) UT,bg.cor =0.22 ±0.13(stat) +0.10 -0.04 (syst). As a function of t', the measured values of this amplitude increase as √(-t') and at larger vertical stroke t' vertical stroke the

Effect of pion mean-field on properties of pions and kaons from heavy-ion collisions

International Nuclear Information System (INIS)

Zheng Yuming; Chu Zili; Wang Hui; Sa Benhao

1996-01-01

The Relativistic Vlasov-Uehling-Uhlenbeck (RVUU) model is used to study the properties of pions and kaons produced in heavy ion collisions. We include the nuclear medium effect on kaon and pion in the model, and simulate pion production and subthreshold kaon production in Kr + Zr reactions at 1 GeV/u. The calculated results show that the attractive pion optical potential changes the final-state pion momentum spectrum, enhancing the yield of pions with low transverse momenta. At the same time it also increases the kaon abundance and modifies the kaon momentum distribution

On two-particle correlations of identical pions

International Nuclear Information System (INIS)

Podgoretskij, M.I.

1991-01-01

The pion generation processes, in which the interference term describing the correlations of identical pions seems to be negative, have been analyzed. It is shown that similar processes can take place, in particular, in nuclear collisions at intermediate energies

Pion-nucleus forward scattering amplitudes at Δ(3,3) energies for π+---12C, 40Ca and 48Ca

International Nuclear Information System (INIS)

Dragoset, W.H. Jr.

1978-01-01

Using the LAMPF P 3 channel, small angle elastic cross sections and total cross sections were measured for π +- -- 12 C, 40 Ca and 48 Ca at incident pion kinetic energies spanning the energy region of the Δ(3,3) resonance. The sigma/sub EL/ experiment employed a spectrometer consisting of two magnets and six MWPC to measure scattering angles and momenta. For the sigma/sub T/ experiment six MWPC were positioned about the target in the beam to measure the deflection or absorption of the incident pions. Both experiments monitored the Jacobian cusp of the π → μ + ν decay to achieve absolute normalization. The two complementary data sets allowed the nuclear forward scattering amplitudes, f/sub N/(0), to be completely determined. The sigma/sub EL/ data were fit by a phenomenological small angle scattering model developed by Bethe and modified by West and Yennie. Due to the presence of nuclear-Coulomb interference in the elastic cross sections, both the magnitude and sign of Re f/sub N/ were determined by the fits. The Re f/sub N/ results were used in the sigma/sub T/ analysis to calculate corrections for the nuclear and nuclear-Coulomb interference amplitudes. Im f/sub N/ was calculated from the sigma/sub T/ results via the optical theorem. The overall self-consistencies of the data were checked by inserting IM f/sub N/ as a fixed parameter into the sigma/sub EL/ fits and comparing the resulting Re f/sub N/ to the original Re f/sub N/. It was determined that Re f/sub N/(0) has a zero near 180 MeV for both 12 C and 40 Ca. For 48 Ca, however, the Re f/sub N/ obtained by fitting with the West-Yennie formula was quite charge dependent and did not exhibit a zero in the energy range investigated. The differences in the 40 Ca, 48 Ca total cross sections were compared to a simple Kisslinger optical model calculation. The model indicated that the RMS neutron radius of 48 Ca exceeds the proton radius by 0.10 +- 0.06 fm

Organizational procedure for the study of pion production and absorption processes on nuclei

International Nuclear Information System (INIS)

Banerjee, M.K.; Walker, G.E.

1983-01-01

For nuclear processes involving pions, such as pion production/absorption or exchange currents, it is shown that a natural organization involves adoption of the πNN vertex function g/sub π/(q 2 )#betta# 5 tau/sub α/, where q is the pion four-momentum and g/sub π/(m/sub π/ 2 )approx. =13.4 is the renormalized pion-nucleon coupling constant. The result is independent of the form and details of any fundamental interaction Lagrangian. The difference between g/sub π/(q 2 )#betta# 5 tau/sub α/ and the fully-dressed πNN vertex function contributes to amplitudes involving more bosons, e.g., scattering amplitudes (πN→πN), production amplitudes (πN→ππN), etc. Such contributions are mediated through either seagull-like terms or P11 intermediate states. It is pointed out that it is neither necessary nor practical to calculate these partial contributions to scattering and production amplitudes. One can always exploit other approaches, theoretical and phenomenological, to make reasonably good models for the full amplitudes. The usual procedure of including the effects of negative energy parts of the nucleon propagator in interaction potentials, exchange currents, etc., is easily included in the present organization. The result is that from scattering amplitudes, etc; the positive energy nucleon poles are deleted but Z graphs are included

Radiative pion-proton scattering

International Nuclear Information System (INIS)

Ho-Kim, Q.; Lavine, J.P.

1977-01-01

The results are presented of a non-relativistic calculation of the π +- proton bremsstrahlung cross section at the pion kinetic energy of 298 MeV for backward photon angles. The pion-nucleon interaction is given by models that are based on the p-wave Chew-Low theory. An interaction current is included in an attempt to make the overall bremsstrahlung amplitude gauge-invariant. The predicted cross sections show little of the expected resonance, and are in fair agreement with the data. The authors have also calculated the cross sections at other kinetic energies, and have studied effects of the off-mass-shell electromagnetic vertex. (Auth.)

Collective flow of pions in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Russkikh, V.N.; Ivanov, Yu.B.

1995-02-01

The transverse-momentum distributions of pions in the Au(1 GeV/nucleon)+Au collisions are analyzed. The calculations are carried out within relativistic meanfield one- and two-fluid models. The rapidity distributions of the mean transverse momentum of pions are found to be fairly sensitive to the nuclear equation of state and, especially, to the stopping power. It is shown that the collective flow of pions in the reaction plane always correlates with the 'hot' flow of nucleons (i.e. those emitted from hot regions of nuclear system), while not always, with the total nucleon flow. This 'hot' nucleon flow can be experimentally singled out by selecting nucleons with sufficiently high transverse momenta. We predict that the 'hot' nucleon flow selected in this way will always correlate with the pion flow. Available experimental data on transverse-momentum spectra of pions are compared with calculations employing various equations of state and stopping power. (orig.)

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.

Two-pion production in photon-induced reactions

Indian Academy of Sciences (India)

A deeper understanding of the situation is anticipated from a detailed experimental study of meson photoproduction from nuclei in exclusive reactions. In the energy regime above the (1232) resonance, the dominant double pion production channels are of particular interest. Double pion photoproduction from nuclei is ...

Analytic coupling and Sudakov effects in exclusive processes: pion and γ*γ→π0 form factors

International Nuclear Information System (INIS)

Stefanis, N.G.

2000-01-01

We develop and discuss in technical detail an infrared-finite factorization and optimized renormalization scheme for calculating exclusive processes, which enables the inclusion of transverse degrees of freedom without entailing suppression of calculated observables, like form factors. This is achieved by employing an analytic, i.e., infrared stable, running strong-coupling α s (Q 2 ) which removes the Landau singularity at Q 2 =Λ QCD 2 by a minimum power-behaved correction. The ensuing contributions to the cusp anomalous dimension - related to the Sudakov form factor - and to the quark anomalous dimension - which controls evolution - lead to an enhancement at high Q 2 of the hard part of exclusive amplitudes, calculated in perturbative QCD, while simultaneously improving its scaling behavior. The phenomenological implications of this framework are analyzed by applying it to the pion's electromagnetic form factor, including the NLO contribution to the hard-scattering amplitude, and also to the pion-photon transition at LO. For the pion wave function, an improved ansatz of the Brodsky-Huang-Lepage type is employed, which includes an effective (constituent-like) quark mass, m q =0.33 GeV. Predictions for both form factors are presented and compared to the experimental data, applying Brodsky-Lepage-Mackenzie commensurate scale setting. We find that the perturbative hard part prevails at momentum transfers above about 20 GeV 2 , while at lower Q 2 values the pion form factor is dominated by Feynman-type contributions. The theoretical prediction for the γ * γ→π 0 form factor indicates that the true pion distribution amplitude may be somewhat broader than the asymptotic one. (orig.)

Minkowski space pion model inspired by lattice QCD running quark mass

Energy Technology Data Exchange (ETDEWEB)

Mello, Clayton S. [Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP (Brazil); Melo, J.P.B.C. de [Laboratório de Física Teórica e Computacional – LFTC, Universidade Cruzeiro do Sul, 01506-000 São Paulo, SP (Brazil); Frederico, T., E-mail: tobias@ita.br [Instituto Tecnológico de Aeronáutica, DCTA, 12.228-900 São José dos Campos, SP (Brazil)

2017-03-10

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.

Minkowski space pion model inspired by lattice QCD running quark mass

Directory of Open Access Journals (Sweden)

Clayton S. Mello

2017-03-01

Full Text Available 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.

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

First amplitude analysis of resonant structures in the 5-pion continuum at COMPASS

International Nuclear Information System (INIS)

Neubert, Sebastian

2012-01-01

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 ∝ 1.6 GeV/c 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 π - π + π - π + π - 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 2 . A partial wave decomposition of the 5π 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 π 2 (1670) and π(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 π 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 search for the subtle effects that would indicate new physics beyond the

Reconstruction of far-field tsunami amplitude distributions from earthquake sources

Science.gov (United States)

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.

Large-angle theory for pion-nucleus scattering at high energies

International Nuclear Information System (INIS)

Hoock, D.W. Jr.

1978-01-01

An approximate solution for high-energy, projectile-nucleus, multiple scattering is developed from the exact Watson series and applied to pion scattering for 12 C and 4 He. Agreement with measured differential cross sections available from the literature for the range 150 to 260 MeV pion laboratory energies is surprisingly good. The approximation method expands the propagators of the Watson series about the transverse component of the momentum transfer. Contributions of each of the first two terms to double scattering from a Gaussian potential are compared to the exact solution. The purely plane-wave propagation produces a scattering amplitude that agrees to order (k 0 a) -1 with the exact solution at the forward and backward directions at high energies. The second (off-axis) propagation term produces an amplitude that is one order smaller at forward angles and two orders smaller at 180 0 than the exact amplitude. At intermediate angles it is of the same order. The general multiple-scattering series is approximated with selection of plane-wave propagation as the fundamental process at large and small angles. This model suggests that a single nucleon accepts most of the momentum transfer for backward scattering. The resulting multiple-scattering formula agrees with the well-known high-energy eikonal theory at small angles and the backward-angle scattering formula of Chen at exactly 180 0 . A lowest-order formula that includes off-axis propagation is also derived. Predicted differential cross sections are found to be sensitive to nucleon motion and binding. For 4 He the effect of the nuclear potential on the pion kinetic energy is also examined and found to produce significant changes in the predicted cross sections

Transverse-target single-spin azimuthal asymmetry in hard exclusive electroproduction of single pions at HERMES

Energy Technology Data Exchange (ETDEWEB)

Hristova, I.

2007-12-15

We present the analysis of data taken in the years 2002-2004 with the 27.56 GeV positron beam of the HERA storage ring at DESY and the internal transversely polarised hydrogen fixed target of the HERMES experiment. Events with a scattered positron and a produced pion are selected. Exclusive production of single pions, e{sup +}p{yields}e{sup +'}n{pi}{sup +}, is ensured by requiring the missing mass in the event to be equal to the mass of the neutron, which is not detected. The cross section for this process depends on the Bjorken scaling variable, the four-momentum transfer, and the transverse four-momentum transfer, whose average values for our sample are left angle x right angle =0.12, left angle Q{sup 2} right angle =2.3 GeV{sup 2}, left angle t' right angle =-0.18 GeV{sup 2}, respectively, and two azimuthal angles: the angle {phi} between the scattering and production planes (their common line contains the virtual photon), and the angle {phi}{sub S} between the scattering plane and the target polarisation vector. The hard scattering is selected by requiring Q{sup 2}>1 GeV{sup 2}. The asymmetry, also called transverse-target single-spin azimuthal asymmetry, is defined as the ratio of the difference to the sum of the cross sections for positive and negative target polarisation. It is characterised by six azimuthal sine modulations, whose amplitudes can vary from -1 to 1. We measure the asymmetry from a sample of 2093 events with a signal-to-background ratio of 1: 1. At average kinematics, the values of the amplitudes are found to be small or consistent with zero, except for the amplitude A{sup sin{phi}{sub SUT,meas}}=0.38{+-}0.06(stat){sup +0.12}{sub -0.06}(syst). The amplitude of main interest for comparison with theory, A{sup sin({phi}-{phi}{sub S})}{sub UT,meas}=0.09{+-}0.05(stat){sup +0.10}{sub -0.03}(syst), after correction for the background contribution becomes A{sup sin({phi}-{phi}{sub S})}{sub UT,bg.cor}=0.22 {+-}0.13(stat){sup +0.10}{sub -0

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.

Absolute determination of the dominant amplitudes of the electroproduction of neutral pions at the momentum transfer of 0,630 GeV2

International Nuclear Information System (INIS)

Bantes, B.

2003-10-01

A complete Monte Carlo simulation for the neutral pion electroproduction experiment in the kinematics of the Δ(1232) that was carried out at the accelerator facility ELSA has been developed to correct the data concerning effects like detector resolution efficiencies, acceptances and radiation corrections. Results for the leading amplitudes are extracted at the four momentum transfer of 0.630 GeV 2 . Absolute cross sections are extracted using the well known elastic ep scattering to determine the luminosity. (orig.)

Direct determination of two-pion correlations for $\\overline{p}p \\to 2\\pi^{+}2\\pi^{-}$ annihilation at rest

CERN Document Server

Angelopoulos, Angelos; Aslanides, Elie; Backenstoss, Gerhard; Bargassa, P; Behnke, O; Benelli, A; Bertin, V; Blanc, F; Bloch, P; Carlson, P J; Carroll, M; Carvalho, J; Cawley, E; Charalambous, S; Chardin, G; Chertok, M B; Cody, A; Danielsson, M; Dejardin, M; Derré, J; Ealet, A; Eleftheriadis, C; Evangelou, I; Faravel, L; Ferreira-Marques, R; Fetscher, W; Fidecaro, Maria; Filipcic, A; Francis, D; Fry, J; Gabathuler, Erwin; Gamet, R; Garreta, D; Gerber, H J; Go, A; Haselden, A; Hayman, P J; Henry-Coüannier, F; Hollander, R W; Hubert, E; Jon-And, K; Kettle, P R; Kokkas, P; Kreuger, R; Le Gac, R; Leimgruber, F; Liolios, A; Machado, E; Mandic, I; Manthos, N; Marel, Gérard; Mikuz, M; Miller, J; Montanet, François; Müller, A; Nakada, Tatsuya; Pagels, B; Papadopoulos, I M; Pavlopoulos, P; Pinto da Cunha, J; Policarpo, Armando; Polivka, G; Rickenbach, R; Roberts, B L; Ruf, T; Sakelliou, L; Sanders, P; Schäfer, M; Schaller, L A; Schietinger, T; Schopper, A; Soares, A; Tauscher, Ludwig; Thibault, C; Touchard, F; Touramanis, C; Triantis, F A; Van Beveren, E; van Eijk, C W E; Vlachos, S; Weber, P; Wigger, O; Wolter, M; Yéche, C; Zavrtanik, D; Zimmerman, D; Locher, M P; Markushin, V E

1998-01-01

We study $\\pi\\pi$ correlations in the exclusive reaction $\\ppb \\to 2\\pi^+2\\pi^-$ at rest measured by the CPLEAR experiment. Avoiding the introduction of an arbitrary reference sample, we analyse differential distributions for equal charge pion pairs removing the phase-space factor event by event. A peak at small relative momenta is most pronounced for large total momentum of the pair. The physical implications of bosonic symmetrization for the properties of the pion source, in particular its radius, are briefly discussed. The two extremes considered are the chaotic Hanbury-Brown--Twiss mechanism and the coherent Skyrmion model.

Distributions of energy losses of electrons and pions in the CBM TRD

International Nuclear Information System (INIS)

Akishina, E.P.; Akishina, T.P.; Ivanov, V.V.; Denisova, O.Yu.

2007-01-01

The distributions of energy losses of electrons and pions in the TRD detector of the CBM experiment are considered. We analyze the measurements of the energy deposits in one-layer TRD prototype obtained during the test beam (GSI, Darmstadt, February 2006) and Monte Carlo simulations for the n-layered TRD realized with the help of GEANT in frames of the CBM ROOT. We show that 1) energy losses both for real measurements and GEANT simulations are approximated with a high accuracy by a log-normal distribution for π and a weighted sum of two log-normal distributions for e; 2) GEANT simulations noticeably differ from real measurements and, as a result, we have a significant loss in the efficiency of the e/π identification. A procedure to control and correct the process of the energy deposit of electrons in the TRD is developed

Pion form factor in QCD at intermediate momentum transfers

Science.gov (United States)

Braun, V. M.; Khodjamirian, A.; Maul, M.

2000-04-01

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 us to estimate the deviation: [∫du/uφπ(u)]/[∫du/uφasπ(u)]=1.1+/-0.1 at the scale of 1 GeV. Special attention is paid to the precise definition and interplay of soft and hard contributions at intermediate momentum transfer, and to the 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 the order of 30% for Q2~1 GeV2.

Pion photoproduction on the nucleon at threshold

International Nuclear Information System (INIS)

Cheon, I.T.; Jeong, M.T.

1989-08-01

Electric dipole amplitudes of pion photoproduction on the nucleon at threshold have been calculated in the framework of the chiral bag model. Our results are in good agreement with the existing experimental data

Relativistic generalizations of simple pion-nucleon models

International Nuclear Information System (INIS)

McLeod, R.J.; Ernst, D.J.

1981-01-01

A relativistic, partial wave N/D dispersion theory is developed for low energy pion-nucleon elastic scattering. The theory is simplified by treating crossing symmetry only to lowest order in the inverse nucleon mass. The coupling of elastic scattering to inelastic channels is included by taking the necessary inelasticity from experimental data. Three models are examined: pseudoscalar coupling of pions and nucleons, pseudovector coupling, and a model in which all intermediate antinucleons are projected out of the amplitude. The phase shifts in the dominant P 33 channel are quantitatively reproduced for P/sub lab/ 33 phase shifts. Thus a model of the pion-nucleon interaction which does not include antinucleon degrees of freedom is found to be unphysical

Experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies

International Nuclear Information System (INIS)

1990-01-01

This report summarizes the work on experimental research in intermediate energy nuclear and particle physics carried out by New Mexico State University in 1988--91. Most of these studies have involved investigations of neutron-proton and pion-nucleus interactions. The neutron-proton research is part of a program of studies of interactions between polarized nucleons that we have been involved with for more than ten years. Its purpose has been to help complete the determination of the full set of ten complex nucleon-nucleon amplitudes at energies up to 800 MeV, as well as to continue investigating the possibility of the existence of dibaryon resonances. The give complex isospin-one amplitudes have been fairly well determined, partly as a result of this work. Our work in this period has involved measurements and analysis of data on elastic scattering and total cross sections for polarized neutrons on polarized protons. The pion-nucleus research continues our studies of this interaction in regions where it has not been well explored. One set of experiments includes studies of pion elastic and double-charge-exchange scattering at energies between 300 and 550 MeV, where our data is unique. Another involves elastic and single-charge-exchange scattering of pions from polarized nuclear targets, a new field of research which will give the first extensive set of information on spin-dependent pion-nucleus amplitudes. Still another involves the first set of detailed studies of the kinematic correlations among particles emitted following pion absorption in nuclei

Inclusive charged and neutral pion photoproduction at 20 GeV

International Nuclear Information System (INIS)

Rickman O'Dell, V.

1987-05-01

The inclusive charged and neutral pion distributions from the interactions of 20 GeV photons on protons have been measured. The assumptions and analysis done to obtain these distributions are described, and the pion distributions are found to agree with general predictions of the quark-parton model. The quark-quark fusion model and the recombination model were compared to the inclusive pion distributions assuming the photon could be approximated by a superposition of rho and omega vector meson states - an assumption prompted by the Vector Meson Dominance Model of photon structure. Quark models applied to the difference in the charged pion cross sections are examined. The inclusive charge structure of the photoproduced charged pions and that of electroproduced and hadroproduced charged pions were compared

Low-energy photo- and electroproduction for physical pions

International Nuclear Information System (INIS)

MacMullen, J.T.

1979-02-01

The background resonance Δ(1230), Nsup(*)(1520), Nsup(*)(1470) and Nsup(*)(1535)pion and axial-vector amplitudes are first calculated in the soft pion and on-shell configuration, respectively. Then a comparison is made with the usual soft pion theorems and on-shell low-energy expansions of current algebra as worked out in the previous paper. The agreement is good and we also deduce a nucleon dipole form factor axial-vector mass of msub(A)approximately equal to 1,23 GeV. Finally an approximate value for the non-strange current quark mass of m equal to 0,64 +- 1,11μ is extracted from the data

The low-energy theorem of pion photoproduction using the Skyrme model

International Nuclear Information System (INIS)

Ikehashi, T.; Ohta, K.

1995-01-01

We reassess the validity of the current-algebra based low-energy theorem of pion photoproduction on the nucleon using the Skyrme model. We find that one of the off-shell electromagnetic form factors of the nucleon exhibits infrared divergence in the chiral limit. This contribution introduces an additional term to the threshold amplitude predicted by the low-energy theorem. The emergence of the additional term indicates an unavoidable necessity of off-shell form factors in deriving the low-energy theorem. In the case of neutral pion production, the new contribution to the threshold amplitude is found to be comparable in magnitude to the low-energy theorem's prediction and has the opposite sign. In the charged pion production channels, the correction to the theorem is shown to be relatively small. (orig.)

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.

Scattering phase shift for elastic two pion scattering and the rho resonance in lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Gutzwiller, Simone

2012-10-08

In this thesis we use lattice QCD to compute scattering phase shifts for elastic two-pion scattering in the isospin I=1 channel. Using Luescher's formalism, we derive the scattering phase shifts for different total momenta of the two-pion system in a non-rest frame. Furthermore we analyse the symmetries of the non-rest frame lattices and construct 2-pion and rho operators transforming in accordance with these symmetries. The data was collected for a 32{sup 3} x 64 and a 40{sup 3} x 64 lattice with N{sub f}=2 clover improved Wilson fermions at a pion mass around 290 MeV and a lattice spacing of about 0.072 fm.

Scattering phase shift for elastic two pion scattering and the rho resonance in lattice QCD

International Nuclear Information System (INIS)

Gutzwiller, Simone

2012-01-01

In this thesis we use lattice QCD to compute scattering phase shifts for elastic two-pion scattering in the isospin I=1 channel. Using Luescher's formalism, we derive the scattering phase shifts for different total momenta of the two-pion system in a non-rest frame. Furthermore we analyse the symmetries of the non-rest frame lattices and construct 2-pion and rho operators transforming in accordance with these symmetries. The data was collected for a 32 3 x 64 and a 40 3 x 64 lattice with N f =2 clover improved Wilson fermions at a pion mass around 290 MeV and a lattice spacing of about 0.072 fm.

Radiobiological work using a negative pion beam at the Rutherford Laboratory 1971-76

International Nuclear Information System (INIS)

Ellis, R.E.; Lindop, P.J.; Coggle, J.E.; Fraser, G.

1976-08-01

The subject is discussed in two sections: physics experiments (including, inter alia, dose measurement, LET distribution, radiation products of spallation); radiobiological studies (including separate reports as follows: review of experimental programme; some in vivo effects of negative pions in mice; survival and recovery of Hela cells in vitro; negative pion dose-response curves for frozen Hela cells; response of vicia faba to irradiation with negative pions; pion experiments with chromosome aberrations). (U.K.)

Pion production in relativistic heavy ion collisions

International Nuclear Information System (INIS)

Norbury, J.W.

1983-01-01

A Lorentz-invariant differential cross section for pion production in peripheral, relativistic, heavy ion collisions is calculated for the collisions of an 16 O projectile onto a 12 C target. The pions are produced via excitations of a Δ(3,3) resonant state in the projectile with simultaneous excitation of an M1 giant resonance in the target. A second order amplitude describing resonance formation and decay is derived within the context of second order, time-dependent perturbation theory and a corresponding transition rate is evaluated. This is then applied to the problem of pion production and a differential cross section is calculated using a simple product-of-states model. The whole theory is then re-formulated within a second quantized particle-hole model which describes the basic process of M1 giant resonance formation as well as the formation and decay of the intermediate Δ(3,3) resonance. Subsequently, a new Lorentz-invariant differential cross section is calculated from the particle-hole amplitude. The theoretical cross section is compared with some experimental data and the agreement is found to be satisfactory given the nature of the data and the assumptions of the theory

ABC's of pion charge exchange

International Nuclear Information System (INIS)

Gibbs, W.R.; Kaufmann, W.B.; Siegel, P.B.

1985-01-01

Calculations of pion single charge exchange using the PWIA and DWIA are presented. Emphasis is given to the effects of absorbtion and blocking. A microscopic calculation of the 0 0 excitation and low energy angular distribution is in excellent agreement with the data. A fixed nucleon multiple scattering calculation of the pion double charge exchange reaction is presented. Various valence neutron wave functions are used, and the contributions of different spatial orientations of the last two neutrons to the reaction are examined. The DCX cross section is found to be very sensitive to the inclusion of correlations in the two-neutron wave function. Satisfactory agreement with DCX data on 14 C can be obtained using a nucleonic picture of the nucleus

Particle Distribution Modification by Low Amplitude Modes

International Nuclear Information System (INIS)

White, R.B.; Gorelenkov, N.; Heidbrink, W.W.; Van Zeeland, M.A.

2009-01-01

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.

Soft and hard contributions to hard pion photoproduction

International Nuclear Information System (INIS)

Afanasev, Andrei; Carlson, Carl E.; Wahlquist, Christian

2000-01-01

Pion photoproduction at high transverse momentum supplements what can be learned in the standard probes of deep inelastic scattering and Drell-Yan processes. With polarized initial states there is sensitivity to the polarized gluon distribution, Δg, in leading order. This contrasts to other processes mentioned, which have no leading order gluon contribution. Additionally, in some kinematic regions the process occurs mainly due to pion production at short distances ('direct pion production', resulting in kinematically isolated pions), which gives sensitivity to the high-x valence quark distribution

Interaction of slow pions with atomic nuclei

International Nuclear Information System (INIS)

Troitskij, M.A.; Tsybul'nikov, A.V.; Chekunaev, N.I.

1984-01-01

Interactions of slow pions with atomic nuclei near to pion condensation are investigated. From comparison of experimental data with the theoretical calculation results on the basis of precise microscopic approach not bound with the random phase approximation (RPA) nuclear matter fundamental parameters near a critical point can be found. Optical potential of slow pions in nuclei, πN-scattering amplitudes and lengths, π-atom level isotopic shift, phenomenon of single-nucleon pion absorption by nucleus, phenomenon of nuclear critical opalescence are considered. The results of πN-scattering lengths calculation, sup(40-44)Ca, sup(24-29)Mg, sup(16-18)O π-atom level shift are presented. It is shown that the presence of π-condensate in nuclei can explain the observed suppression of p-wave potential terms. The phenomenon of single-nucleon pion absorption by nucleus is one of direct experiments which permits to reveal the π-condensate. The nuclear opalescence phenomenon is manifested in increase of pion photoproduction reaction cross section for account of nucleus proximity to π-condensation as compared with the calculated in the Fermi-gas model. The suggested method for calculating precondensate phenomena operates the better, the nearer is the system to the condensation threshold whereas the RPA method in this region is inapplicable

Tensor polarization in pion-deuteron elastic scattering

International Nuclear Information System (INIS)

Holt, R.J.

1983-01-01

The angular dependence of the tensor polarization t 20 /sup lab/ of recoiling deuterons in π-d elastic scattering was measured as a function of incident pion energy in the range 134 to 256 MeV. No evidence was found for rapid energy or angular dependences in t 20 /sup lab/. The results agree most favorably with theoretical calculations in which the P 11 π-N amplitude has been removed altogether. This agreement is consistent with a small effect of pion absorption on the elastic channel. 14 references

Dynamical chiral symmetry breaking and pion decay constant

International Nuclear Information System (INIS)

Gogohia, V.Sh.; Kluge, Gy.

1991-08-01

Flavour non-singlet, chiral axial-vector Ward-Takahashi identity is investigated in the framework of dynamical chiral symmetry breaking. The use of the condition of stationarity for the bound-state amplitude is proposed in order to fully determine this quantity and the regular piece of the corresponding axial vertex. This makes it possible to express the pion decay constant in terms of the quark propagator variables only. An exact expression was found for the pion decay constant in current algebra and in Jackiw-Johnson representation as well. We also find a new expression for the pion decay constant in the Pagels-Stokar-Cornwall variables within the framework of Jackiw-Johnson representation. (author) 22 refs.; 2 figs

Energy-independent multipole analysis of single-pion photoproduction from protons

Energy Technology Data Exchange (ETDEWEB)

Get' man, V.A.; Sanin, V.M.; Telegin, Y.N.; Shalatskii, S.V.

1983-08-01

For the first time photoproduction multipole amplitudes are evaluated unambiguously on the basis of new experimental data on pion photoproduction from protons and the latest ..pi..N scattering phase shifts. The multipole amplitudes obtained are compared with the results of previous multipole analyses and dispersion-relation predictions.

Energy-independent multipole analysis of single-pion photoproduction from protons

International Nuclear Information System (INIS)

Get'man, V.A.; Sanin, V.M.; Telegin, Y.N.; Shalatskii, S.V.

1983-01-01

For the first time photoproduction multipole amplitudes are evaluated unambiguously on the basis of new experimental data on pion photoproduction from protons and the latest πN scattering phase shifts. The multipole amplitudes obtained are compared with the results of previous multipole analyses and dispersion-relation predictions

Pion inclusive momentum distribution at 900 in hydrodynamical model

International Nuclear Information System (INIS)

Chiu, C.B.; Wang, K.H.

1975-01-01

It is shown that pion inclusive momentum distributions in pp-collisions at 90 0 up to FNAL and ISR energies can be accounted for by a hydrodynamical model, which has frame independence symmetry and incorporates the evaporation phenomena. Within the solution during its space--time development, the matter system only possesses a local thermal equilibrium but not a global equilibrium. The proper time interval needed to achieve this equilibrium comes out to be comparable to (with c = 1) the longitudinal dimension estimated previously based on considerations of quantum statistical fluctuation. (U.S.)

Strange Twists in Neutral Pion Photo/Electro-Production

OpenAIRE

Meißner, Ulf-G.

1995-01-01

I review the interesting tale of the electric dipole amplitude in neutral pion photoproduction and the resulting consequences. I also discuss why there is new life related to P--wave multipoles. Electroproduction is briefly touched upon.

Two-Loop Splitting Amplitudes

International Nuclear Information System (INIS)

Bern, Z.

2004-01-01

Splitting amplitudes govern the behavior of scattering amplitudes at the momenta of external legs become collinear. In this talk we outline the calculation of two-loop splitting amplitudes via the unitarity sewing method. This method retains the simple factorization properties of light-cone gauge, but avoids the need for prescriptions such as the principal value or Mandelstam-Leibbrandt ones. The encountered loop momentum integrals are then evaluated using integration-by-parts and Lorentz invariance identities. We outline a variety of applications for these splitting amplitudes

Two-loop splitting amplitudes

International Nuclear Information System (INIS)

Bern, Z.; Dixon, L.J.; Kosower, D.A.

2004-01-01

Splitting amplitudes govern the behavior of scattering amplitudes at the momenta of external legs become collinear. In this talk we outline the calculation of two-loop splitting amplitudes via the unitarity sewing method. This method retains the simple factorization properties of light-cone gauge, but avoids the need for prescriptions such as the principal value or Mandelstam-Leibbrandt ones. The encountered loop momentum integrals are then evaluated using integration-by-parts and Lorentz invariance identities. We outline a variety of applications for these splitting amplitudes

Bethe-Salpeter analysis of the radiative pion disintegration

Energy Technology Data Exchange (ETDEWEB)

Abad, J.; Pacheco, A.F. (Zaragoza Univ. (Spain). Dept. de Fisica Teorica); Rodriguez-Trias, R.; Esteve, J.G. (Paris-11 Univ., 91 - Orsay (France). Lab. de Physique Theorique et Hautes Energies)

1990-04-01

The structure-dependent amplitude of the decay {pi}{yields}e{nu}{gamma} is evaluated in the framework of a Bethe-Salpeter description for the pion. We assume a general B-S wave function in the S-wave. Within this hypothesis, we show that the gauge invariance constrains the different contributions of the wave functions to the amplitude, resulting in the vanishing of the axial form factor. (orig.).

Evidence for delta-hole components from pion reactions

International Nuclear Information System (INIS)

Morris, C.L.

1982-01-01

Some anomalies observed in pion-induced reactions have been qualitatively explained with a model which includes Δ 3 3 admixtures in low lying nuclear states. Semi-quantitative analysis of these effects indicates the amplitudes for the Δ 3 3 admixtures necessary to explain these effects are on the order of a few percent. Although a more rigorous theoretical treatment of this problem is necessary, it appears that pion-induced reactions may provide a tool with which the spectroscopy of these Δ 3 3 -admixtures can be studied

Real-pion states formed by virtual-pion beam

International Nuclear Information System (INIS)

Yamazaki, Toshimitsu.

1990-04-01

Deeply bound pionic states are discussed from various points of view; highly excited nuclear states as a cluster family of pionic bound states, Σ atom/Σ hypernuclei, halo-like density distributions, virtual pion beam to produce pionic states, etc. (author)

Beam energy and centrality dependence of two-pion Bose-Einstein correlations at SPS energies

International Nuclear Information System (INIS)

Adamova, D.; Agakichiev, G.; Appelshaeuser, H.; Belaga, V.; Braun-Munzinger, P.; Campagnolo, R.; Castillo, A.; Cherlin, A.; Damjanovic, S.; Dietel, T.; Dietrich, L.; Drees, A.; Esumi, S.I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glaessel, P.; Hering, G.; Holeczek, J.; Kushpil, V.; Lenkeit, B.; Ludolphs, W.; Maas, A.; Marin, A.; Milosevic, J.; Milov, A.; Miskowiec, D.; Musa, L.; Panebrattsev, Yu.; Petchenova, O.; Petracek, V.; Pfeiffer, A.; Rak, J.; Ravinovich, I.; Rehak, P.; Richter, M.; Sako, H.; Schmitz, W.; Schukraft, J.; Sedykh, S.; Seipp, W.; Sharma, A.; Shimansky, S.; Slivova, J.; Specht, H.J.; Stachel, J.; Sumbera, M.; Tilsner, H.; Tserruya, I.; Wessels, J.P.; Wienold, T.; Windelband, B.; Wurm, J.P.; Xie, W.; Yurevich, S.; Yurevich, V.V.

2003-01-01

Results are presented of a two-pion interferometry (HBT) analysis in Pb+Au collisions at 40, 80, and 158 A GeV. A detailed study of the Bertsch-Pratt HBT radius parameters has been performed as function of the mean pair transverse momentum k t and in bins of the centrality of the collision. From these results we extract model-dependent information about the space-time evolution of the reaction. An investigation of the effective volume of the pion emitting system provides an important tool to study the properties of thermal pion freeze-out

Beam energy and centrality dependence of two-pion Bose-Einstein correlations at SPS energies

Energy Technology Data Exchange (ETDEWEB)

Adamova, D.; Agakichiev, G.; Appelshaeuser, H. E-mail: appels@physi.uni-heidelberg.de; Belaga, V.; Braun-Munzinger, P.; Campagnolo, R.; Castillo, A.; Cherlin, A.; Damjanovic, S.; Dietel, T.; Dietrich, L.; Drees, A.; Esumi, S.I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glaessel, P.; Hering, G.; Holeczek, J.; Kushpil, V.; Lenkeit, B.; Ludolphs, W.; Maas, A.; Marin, A.; Milosevic, J.; Milov, A.; Miskowiec, D.; Musa, L.; Panebrattsev, Yu.; Petchenova, O.; Petracek, V.; Pfeiffer, A.; Rak, J.; Ravinovich, I.; Rehak, P.; Richter, M.; Sako, H.; Schmitz, W.; Schukraft, J.; Sedykh, S.; Seipp, W.; Sharma, A.; Shimansky, S.; Slivova, J.; Specht, H.J.; Stachel, J.; Sumbera, M.; Tilsner, H.; Tserruya, I.; Wessels, J.P.; Wienold, T.; Windelband, B.; Wurm, J.P.; Xie, W.; Yurevich, S.; Yurevich, V.V

2003-02-10

Results are presented of a two-pion interferometry (HBT) analysis in Pb+Au collisions at 40, 80, and 158 A GeV. A detailed study of the Bertsch-Pratt HBT radius parameters has been performed as function of the mean pair transverse momentum k{sub t} and in bins of the centrality of the collision. From these results we extract model-dependent information about the space-time evolution of the reaction. An investigation of the effective volume of the pion emitting system provides an important tool to study the properties of thermal pion freeze-out.

Generalized Veneziano model for pion scattering off isovector currents and the scaling limit

CERN Document Server

Rothe, H J; Rolhe, K D

1972-01-01

Starting from a local one-particle approximation scheme for the commutator of two conserved currents, the authors construct a generalized Veneziano model for pion scattering off neutral and charged isovector currents, satisfying the constraints of current conservation and current algebra. The model factorizes correctly on the leading Regge trajectories and incorporates the proper Regge behaviour for strong amplitudes. Fixed poles are found to be present in the s and t channels of the one- and two-current amplitudes. Furthermore, the model makes definite predictions about the structure of Schwinger terms and of the 'seagull' terms in the retarded commutator. (13 refs).

Toy model for pion production in nucleon-nucleon collisions

International Nuclear Information System (INIS)

Hanhart, C.; Miller, G. A.; Myhrer, F.; Sato, T.; Kolck, U. van

2001-01-01

We develop a toy model for pion production in nucleon-nucleon collisions that reproduces some of the features of the chiral Lagrangian calculations. We calculate the production amplitude and examine some common approximations

Study of the baryon-baryon interaction in nucleon-nucleon and pion-deuteron scattering

International Nuclear Information System (INIS)

Fuchs, M.

1993-01-01

After the definition of the Hamiltonian in general form by meson production and absorption the transition to operators pursued, which connect only spaces with definite meson numbers. In this approximation first the self-energy of a single baryon was calculated in its full energy and momentum dependence. Then the formal expressions for the T matrices of nucleon-nucleon and pion-deuteron scattering were derived. The essential components of these expressions are the baryon-baryon T matrix ant transition amplitudes from pion-deuteron channels to baryon-baryon states. The central chapter dealt with the calculation of the baryon-baryon interaction for the general form of the vertices, with the solution of the binding problem and the baryon-baryon T matrix. Finally followed the results on the nucleon-nucleon and pion-deuteron scattering. For this first the transition amplitudes from pion-deuteron states to intermediate baryon-baryon states and the Born graphs of the pion-deuteron scattering had to be calculated. After some remarks to the transition from partial-wave decomposed T matrices to scattering observables an extensive representation of the total, partial, and differential cross sections and a series of spin observables (analyzing powers and spin correlations) for the elastic proton-proton, neutron-proton, and pion-deuteron scattering as well for the fusion reaction pp→πd and the breakup reaction πd→pp follows. Thereby the energies reached from the nucleon-nucleon respectively pion-deuteron threshold up to 100 MeV above the delta resonance

Effects of the pion string at heavy ion collisions

International Nuclear Information System (INIS)

Mao Hong; Li Yunde; East China Normal Univ., Shanghai

2005-01-01

The authors study the possible signals of the pion string associated with the QCD chiral phase transition in LHC Pb-Pb collision at energy √s=5.5 TeV. The authors follow the Kibble-Zurek mechanism to discuss the production and evolution of the pion string. The authors will show that if the QCD chiral phase transition really takes place in the LHC Pb-Pb collision process and the phase transition is in the second order, the pion string will be inevitably produced and subsequently decay. The main effect of this phenomenon is that there is a generation of a large number of pions in the final state produced by the decay of the pion string, and these pions are mostly distributed in a low momentum region with p-143 MeV; also there are lots of neutral pions distributed in a low momentum region with the mean momentum at p-21 MeV. (authors)

Effects of the pion string at heavy ion collisions

CERN Document Server

Mao, Hong

2005-01-01

We study the possible signals of the pion string associated with the QCD chiral phase transition in LHC Pb-Pb collision at energy square root s=5.5 TeV. We follow the Kibble-Zurek mechanism to discuss the production and evolution of the pion string. We will show that if the QCD chiral phase transition really takes place in the LHC Pb-Pb collision process and the phase transition is in the second order, the pion string will be inevitably produced and subsequently decay. The main effect of this phenomenon is that there is a generation of a large number of pions in the final state produced by the decay of the pion string, and these pions are mostly distributed in a low momentum region with p143 MeV; also there are lots of neutral pions distributed in a low momentum region with the mean momentum at p21 Me V.

Pion production cross sections and associated parameters

International Nuclear Information System (INIS)

Bradbury, J.N.

1985-01-01

Negative pions have been used for radiotherapy at the meson factories LAMPF (USA), SIN (Switzerland), and TRIUMF (Canada) and have been planned for use at new meson facilities under construction (USSR) and at proposed dedicated medical facilities. Providing therapeutically useful dose rates of pions requires a knowledge of the pion production cross sections as a function of primary proton energy (500 to 1000 MeV), pion energy (less than or equal to100 MeV), production angle, and target material. The current status of the data base in this area is presented including theoretical guidelines for extrapolation purposes. The target material and geometry, as well as the proton and pion beam parameters, will affect the electron (and muon) contamination in the beam which may have an important effect on both the LET characteristics of the dose and the dose distribution. In addition to cross-section data, channel characteristics such as length of pion trajectory, solid-angle acceptance, and momentum analysis will affect dose rate, distribution, and quality. Such considerations are briefly addressed in terms of existing facilities and proposed systems. 16 refs., 6 figs

Proton multiplicity distributions in pion-xenon nucleus collisions at 3.5 GeV/c

International Nuclear Information System (INIS)

Strugalski, Z.; Pawlak, T.; Peryt, W.; Pluta, J.

1980-01-01

Experimental results from the proton emission investigation in 3.5 GeV/c pion minus-xenon nucleus collisions detected in the 180 xenon bubble chamber are presented and analyzed. The emitted protons are of kinetic energies from 20 to 400 MeV. Multiplicity distributions of protons both accompanied and not accompanied by secondary charged and neutral pions are given. Large proton multiplicities are observed in the events without multiparticle production, the proton multiplicity distribution in this class of events being of an irregular character. The experimental results are well described in the model based on the following hypothesis: a high energy hadron traversing the target causes the monotonous emission of the fast protons in numbers nsub(p) being equal to the number of protons encountered in the neighbourhood of its path inside the nucleus target. In this case the multiple production goes through some intermediate states which decay after having left the target nucleus

Two pion mediated scalar isoscalar NN interaction in the nuclear medium

International Nuclear Information System (INIS)

Kaskulov, Murat M.; Oset, E.; Vacas, M.J. Vicente

2006-01-01

We study the modification of the nucleon-nucleon interaction in a nuclear medium in the scalar isoscalar channel, mediated by the exchange of two correlated (σ channel) or uncorrelated pions. For this purpose we use a standard approach for the renormalization of pions in nuclei. The corrections obtained for the NN interaction in the medium in this channel are of the order of 20% of the free one in average, and the consideration of short-range correlations plays an important role in providing these moderate changes. Yet, the corrections are sizable enough to suggest further studies of the stability and properties of nuclear matter

Pions in nuclei, from virtual-pion exchange to real-pion transfer

International Nuclear Information System (INIS)

Yamazaki, Toshimitsu.

1988-07-01

Tracing the work of Miyazawa on nuclear magnetic moments, we discuss possible experimental ways to see whether a real pion exists in nuclei or not. While virtual pions are known to play an important role in nuclei, as clarified experimentally from anomalous orbital g factors of nucleons in nuclei, nearly nothing is known for the behavior of real pions in nuclei. We have shown that deeply bound hybrid states of π - are expected to exist in heavy nuclei, which can be populated by ''pion transfer'' reactions. (author)

Single- and double-charge exchange at low pion energies

International Nuclear Information System (INIS)

Baer, H.W.

1991-01-01

A review is given of pion single- and double-charge exchange reactions at incident energies of 25 to 65 MeV leading to isobaric analog states, and in the case of double-charge exchange leading to the ground state of the residual nucleus. The crucial role of the higher nuclear transparency at low pion energies for the analysis of the data in terms of single and double scattering is demonstrated. The large effects on double-charge exchange produced by the spatial correlations in nuclear wave functions are evident. The data on 1f 7/2 nuclei at 35 MeV are used to establish the general validity of a shell-model-based two-amplitude model for these transitions. Recent measurements of the energy dependence between 25 and 65 MeV of double-charge exchange cross sections at forward angles are presented and discussed. 33 refs., 19 figs

Two-Pion Correlation Measurements for 14.6 A.GEV/C SILICON-28 + X and 11.6 A.GEV/C GOLD-197 + Gold.

Science.gov (United States)

Soltz, Ron A.

Two-pion correlation functions have been measured in the central rapidity regions (1.5 < y < 2.0) for 14.6 A cdot GeV/c Si+Au to 2 pi^-+rm X (central and peripheral), Si+Al to 2pi^++ rm X (central and minimum bias), Si+Au to 2pi^++rm X (central), and 11.6 A cdot GeV/c Au+Au to 2pi^ -+rm X (central) systems. Two-dimensional fits in R-tau and R_{T}-R_ {L} were performed for these systems for different cuts in the total charged particle multiplicity and forward energy. The R, R_{T}, and R_{L} radius parameters for systems involving the Si projectile were found to increase with increasing charged particle multiplicity. These parameters were observed to scale linearly with A _sp{pp}{1/3}, where A_{pp} is the number of projectile participants as calculated from the forward energy deposition. The correlation functions were also fit to several three-dimensional functions. In all cases these fits proved to be consistent with the results of the two-dimensional fits. Events generated from the RQMD cascade code indicate that pions within experimental acceptance are produced from a region that is smaller than the entire region of pion production. A direct measure of the RQMD source for pions within the acceptance show qualitative agreement with the observed scaling. A minimization function was developed which is derived from the Poisson fluctuations in both the actual and background distributions. Progress was made in understanding the errors of event-mixed background distributions. An empirical study confirms that fluctuations within a bin are indeed Poisson for typical backgrounds generated during this analysis. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Four Pion Final States with Tagged Photons at Electron Positron Colliders

CERN Document Server

Czyz, H

2001-01-01

A Monte Carlo generator has been constructed to simulate the reaction e^+e^- \\to \\gamma + 4 \\pi, where the photon is assumed to be observed in the detector. Isospin relations between the amplitudes governing tau decays into four pions and electron positron annihilation into four pions respectively have been found which allow to determine all four modes after the amplitude for the \\pi^+\\pi^-2\\pi^0 channel has been fixed. The kinematic breaking of these isospin relations as a consequence of the \\pi^- -- \\pi^0 mass difference has also been investigated. The program is constructed in analogy to an earlier one simulating e^+e^- \\to \\gamma + 2 \\pi. However, it does not include final state radiation from the charged pions. Additional collinear photon radiation has been incorporated with the technique of structure functions. Predictions are presented for cms energies of 1GeV, 3GeV and 10GeV, corresponding to the energies of DAPHNE, BEBC and of B-meson factories. Using this program it is demonstrated that, even after ...

Neutral pion electroproduction off light nuclei in chiral perturbation theory

International Nuclear Information System (INIS)

Lenkewitz, Mark

2013-01-01

Threshold pion electroproduction on tri-nucleon systems is investigated in the framework of baryon Chiral Perturbation Theory (ChPT) at next-to-leading one-loop order O(q 4 ) in the chiral expansion. To this order in small momenta, the production operator is a sum of one- and two-nucleon terms. While the one-nucleon terms resemble the impulse approximation, the two-nucleon contributions represent corrections due to the relevant nuclear interactions, e.g. pion-exchange interactions, which prove to be dominant, and due to recoil effects of the participating nucleons, which appear to be negligible. We calculate the expectation value of the production operator using chiral wave functions in a three-dimensional approach without partial wave expansion. The resulting integrals are evaluated using adaptive Monte Carlo integration, the VEGAS algorithm of Lepage. We obtain results for the threshold production multipoles E 0+ and L 0+ on 3 He and 3 H and comment on the sensitivity to the fundamental neutron amplitude E 0+ π 0 n . 3 He appears to be a particularly promising target to extract information about the neutron amplitude. This idea is usually invoked for spin-dependent quantities since the 3 He wave function is strongly dominated by the principal S-state component which suggests that its spin is largely driven by the one of the neutron.

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.

ψ(2S)→π+π-J/ψ decay distributions

International Nuclear Information System (INIS)

Bai, J. Z.; Ban, Y.; Bian, J. G.; Blum, I.; Chen, G. P.; Chen, H. F.; Chen, J.; Chen, J. C.; Chen, Y.; Chen, Y. B.

2000-01-01

Using a sample of 3.8 M ψ(2S) events accumulated with the BES detector, the process ψ(2S)→π + π - J/ψ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/ψ-(π + π - ) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter κ, predicts that D wave pions should be present. We determine κ=0.183±0.002±0.003 based on the joint m ππ -cos θ π * distribution. The fraction of D wave amplitude as a function of m ππ is found to decrease with increasing m ππ , in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. (c) 2000 The American Physical Society

Enhancements observed in the two-proton invariant mass distribution in the pionless deuteron breakup at 3.3 GeV/c

International Nuclear Information System (INIS)

Dolidze, M.G.; Glagolev, V.V.; Kacharava, A.K.

1986-01-01

A sample of ''non-spectator'' events in the pionless deuteron breakup at a 3.3 Gev/c momentum has been investigated by means of a 1m hydrogen bubble chamber at JINR, Dubna. The two-proton invariant mass spectrum in the charge exchange channel exibits two enhancements for masses of 2010 MeV/c 2 and 2160 Mev/c 2 . Theoretical calculations taking into account one-pion exchange diagrams and virtual pion absorption by the deuteron have been carried out. It has been shown that the enhancement at Msub(pp) = 2010 MeV/c 2 can be explained if there is an irregularity in the behaviour of the off-energy-shell amplitude of the πsup(+)d→pp reaction near the threshold. The observed maximum at Msub(pp) = 2160 Mev/c 2 is caused mainly by intermediate Δ production and pion absorption on the deuteron

Coherent pion production induced by protons and light ions

International Nuclear Information System (INIS)

Fernandez de Cordoba, P.; Oset, E.; Vicente-Vacas, M.J.

1995-01-01

We study coherent pion production by means of the (p,n) and (He,t) reactions on different nuclei and at different energies of the projectile. Energy and angular distributions are calculated. The angular distributions are rather narrow along the direction of the momentum transfer, particularly in heavy nuclei. The reaction is sensitive to the longitudinal part of the elementary NN→NΔ interaction. It also provides a new tool to obtain information on the pion-nuclear interaction, complementary to that offered by reactions with real pions. (orig.)

Chiral approach to nuclear matter: Role of two-pion exchange with virtual delta-isobar excitation

OpenAIRE

Fritsch, S.; Kaiser, N.; Weise, W.

2004-01-01

We extend a recent three-loop calculation of nuclear matter in chiral perturbation theory by including the effects from two-pion exchange with single and double virtual $\\Delta(1232)$-isobar excitation. Regularization dependent short-range contributions from pion-loops are encoded in a few NN-contact coupling constants. The empirical saturation point of isospin-symmetric nuclear matter, $\\bar E_0 = -16 $MeV, $\\rho_0 = 0.16 $fm$^{-3}$, can be well reproduced by adjusting the strength of a two-...

Pion-nuclear many body problems

International Nuclear Information System (INIS)

Weise, W.

1981-01-01

This chapter examines pion-nucleus scattering data produced at the meson factories in order to gain information about the ''optical'' branches of the pion-nuclear excitation spectrum. Discusses basic meson-baryon effective Lagrangians and elementary processes; pion-baryon vertex form factors; the spin-isospin dependent baryon-baryon interaction; pions in nuclear matter; nuclear spin-isospin correlations; the baryon-hole model; photon-induced excitation of baryon-hole states; high momentum transfer properties of pion-like nuclear states; a response function for pionic low-frequency modes in finite nuclei; and applications. Finds that there is no clear evidence for pionic critical opalescence, as in agreement with the expectation that the minimal density for the appearance of a pion condensate is certainly not lower than two or three times nuclear matter density

Watson's theorem and resonant pion photoproduction amplitude in the delta channel

International Nuclear Information System (INIS)

Wittman, R.; Davidson, R.; Mukhopadhyay, N.C.

1984-01-01

The CGLN and BL theories of the pion photoproduction on nucleons, used in nuclear calculations, are examined regarding their predictions of the resonant M 1 + and E 1 + multipoles. The nonunitary BL approach violates Watson's theorem, and predicts these multipoles porly. In the static limit, the CGLN multipoles satisfy Watson's theorem and are in fine agreement with data. The unitarized BL multipoles agree with those from the Olsson theory and data. (orig.)

Energy dependence of negatively charged pion production in proton-proton interactions at the CERN SPS

CERN Document Server

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...

Renormalization of NN Interaction with Relativistic Chiral Two Pion Exchange

Energy Technology Data Exchange (ETDEWEB)

Higa, R; Valderrama, M Pavon; Arriola, E Ruiz

2007-06-14

The renormalization of the NN interaction with the Chiral Two Pion Exchange Potential computed using relativistic baryon chiral perturbation theory is considered. The short distance singularity reduces the number of counter-terms to about a half as those in the heavy-baryon expansion. Phase shifts and deuteron properties are evaluated and a general overall agreement is observed.

Numerology on pion and proton rapidity

International Nuclear Information System (INIS)

Gugelot, P.C.

1987-01-01

The pseudo-rapidity of pion jets which were measured for 50 GeV and 150 GeV incident pions and protons on carbon, copper and lead targets is analysed. The shape of the rapidity distribution for a ''fireball'' which emits particles isotropically in its center of mass is a cosh -2 y distribution. It is possible to unfold all measured distributions into three groups which correspond to a low rapidity originating from the target fragmentation, a middle group which is a function of the center of mass of the projectile and target rapidity and a fast group which is due to the projectile. 11 refs., 8 figs. (author)

Deeply virtual compton scattering on a virtual pion target

International Nuclear Information System (INIS)

Amrath, D.; Diehl, M.; Lansberg, J.P.; Heidelberg Univ.

2008-07-01

We study deeply virtual Compton scattering on a virtual pion that is emitted by a proton. Using a range of models for the generalized parton distributions of the pion, we evaluate the cross section, as well as the beam spin and beam charge asymmetries in the leading-twist approximation. Studying Compton scattering on the pion in suitable kinematics puts high demands on both beam energy and luminosity, and we find that the corresponding requirements will first be met after the energy upgrade at Jefferson Laboratory. As a by-product of our study, we construct a parameterization of pion generalized parton distributions that has a non-trivial interplay between the x and t dependence and is in good agreement with form factor data and lattice calculations. (orig.)

Two-pion Bose-Einstein correlations in central PbPb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV

CERN Document Server

Aamodt, K.; Adamova, D.; Adare, A.M.; Aggarwal, M.M.; Aglieri Rinella, G.; Agocs, A.G.; Aguilar Salazar, S.; Ahammed, Z.; Ahmad, N.; Masoodi, A.Ahmad; Ahn, S.U.; Akindinov, A.; Aleksandrov, D.; Alessandro, B.; Molina, R.Alfaro; Alici, A.; Alkin, A.; Almaraz Avina, E.; Alt, T.; Altini, V.; Altinpinar, S.; Altsybeev, I.; Andrei, C.; Andronic, A.; Anguelov, V.; Anson, C.; Anticic, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshauser, H.; Arbor, N.; Arcelli, S.; Arend, A.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I.C.; Asryan, A.; Augustinus, A.; Averbeck, R.; Awes, T.C.; Aysto, J.; Azmi, M.D.; Bach, M.; Badala, A.; Baek, Y.W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Ferroli, R.Baldini; Baldisseri, A.; Baldit, A.; Ban, J.; Barbera, R.; Barile, F.; Barnafoldi, G.G.; Barnby, L.S.; Barret, V.; Bartke, J.; Basile, M.; Bastid, N.; Bathen, B.; Batigne, G.; Batyunya, B.; Baumann, C.; Bearden, I.G.; Beck, H.; Belikov, I.; Bellini, F.; Bellwied, R.; Belmont-Moreno, E.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdermann, E.; Berdnikov, Y.; Betev, L.; Bhasin, A.; Bhati, A.K.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielcik, J.; Bielcikova, J.; Bilandzic, A.; Biolcati, E.; Blanc, A.; Blanco, F.; Blanco, F.; Blau, D.; Blume, C.; Boccioli, M.; Bock, N.; Bogdanov, A.; Boggild, H.; Bogolyubsky, M.; Boldizsar, L.; Bombara, M.; Bombonati, C.; Book, J.; Borel, H.; Bortolin, C.; Bose, S.; Bossu, F.; Botje, M.; Bottger, S.; Boyer, B.; Braun-Munzinger, P.; Bravina, L.; Bregant, M.; Breitner, T.; Broz, M.; Brun, R.; Bruna, E.; Bruno, G.E.; Budnikov, D.; Buesching, H.; Busch, O.; Buthelezi, Z.; Caffarri, D.; Cai, X.; Caines, H.; Calvo Villar, E.; Camerini, P.; Canoa Roman, V.; Cara Romeo, G.; Carena, F.; Carena, W.; Carminati, F.; Casanova Diaz, A.; Caselle, M.; Castillo Castellanos, J.; Catanescu, V.; Cavicchioli, C.; Cerello, P.; Chang, B.; Chapeland, S.; Charvet, J.L.; Chattopadhyay, S.; Chattopadhyay, S.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chiavassa, E.; Chibante Barroso, V.; Chinellato, D.D.; Chochula, P.; Chojnacki, M.; Christakoglou, P.; Christensen, C.H.; Christiansen, P.; Chujo, T.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Coccetti, F.; Coffin, J.P.; Coli, S.; Conesa Balbastre, G.; Conesa del Valle, Z.; Constantin, P.; Contin, G.; Contreras, J.G.; Cormier, T.M.; Corrales Morales, Y.; Cortes Maldonado, I.; Cortese, P.; Cosentino, M.R.; Costa, F.; Cotallo, M.E.; Crescio, E.; Crochet, P.; Cuautle, E.; Cunqueiro, L.; D'Erasmo, G.; Dainese, A.; Dalsgaard, H.H.; Danu, A.; Das, D.; Das, I.; Dash, A.; Dash, S.; De, S.; De Azevedo Moregula, A.; de Barros, G.O.V.; De Caro, A.; De Cataldo, G.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; De Remigis, R.; de Rooij, R.; Delagrange, H.; Delgado Mercado, Y.; Dellacasa, G.; Deloff, A.; Demanov, V.; Denes, E.; Deppman, A.; Di Bari, D.; Di Giglio, C.; Di Liberto, S.; Di Mauro, A.; Di Nezza, P.; Dietel, T.; Divia, R.; Djuvsland, O.; Dobrin, A.; Dobrowolski, T.; Dominguez, I.; Donigus, B.; Dordic, O.; Driga, O.; Dubey, A.K.; Ducroux, L.; Dupieux, P.; Dutta Majumdar, A.K.; Dutta Majumdar, M.R.; Elia, D.; Emschermann, D.; Engel, H.; Erdal, H.A.; Espagnon, B.; Estienne, M.; Esumi, S.; Evans, D.; Evrard, S.; Eyyubova, G.; Fabjan, C.W.; Fabris, D.; Faivre, J.; Falchieri, D.; Fantoni, A.; Fasel, M.; Fearick, R.; Fedunov, A.; Fehlker, D.; Fekete, V.; Felea, D.; Feofilov, G.; Fernandez Tellez, A.; Ferretti, A.; Ferretti, R.; Figueredo, M.A.S.; Filchagin, S.; Fini, R.; Finogeev, D.; Fionda, F.M.; Fiore, E.M.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Fragkiadakis, M.; Frankenfeld, U.; Fuchs, U.; Furano, F.; Furget, C.; Fusco Girard, M.; Gaardhoje, J.J.; Gadrat, S.; Gagliardi, M.; Gago, A.; Gallio, M.; Ganoti, P.; Garabatos, C.; Gemme, R.; Gerhard, J.; Germain, M.; Geuna, C.; Gheata, A.; Gheata, M.; Ghidini, B.; Ghosh, P.; Girard, M.R.; Giraudo, G.; Giubellino, P.; Gladysz-Dziadus, E.; Glassel, P.; Gomez, R.; Gonzalez-Trueba, L.H.; Gonzalez-Zamora, P.; Gonzalez Santos, H.; Gorbunov, S.; Gotovac, S.; Grabski, V.; Grajcarek, R.; Gramling, J.L.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Gros, P.; Grosse-Oetringhaus, J.F.; Grossiord, J.Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerra Gutierrez, C.; Guerzoni, B.; Gulbrandsen, K.; Gulkanyan, H.; Gunji, T.; Gupta, A.; Gupta, R.; Gutbrod, H.; Haaland, O.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Harris, J.W.; Hartig, M.; Hasch, D.; Hasegan, D.; Hatzifotiadou, D.; Hayrapetyan, A.; Heide, M.; Heinz, M.; Helstrup, H.; Herghelegiu, A.; Hernandez, C.; Herrera Corral, G.; Herrmann, N.; Hetland, K.F.; Hicks, B.; Hille, P.T.; Hippolyte, B.; Horaguchi, T.; Hori, Y.; Hristov, P.; Hrivnacova, I.; Huang, M.; Huber, S.; Humanic, T.J.; Hwang, D.S.; Ichou, R.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Incani, E.; Innocenti, G.M.; Innocenti, P.G.; Ippolitov, M.; Irfan, M.; Ivan, C.; Ivanov, A.; Ivanov, M.; Ivanov, V.; Jacholkowski, A.; Jacobs, P.M.; Jancurova, L.; Jangal, S.; Janik, R.; Jayarathna, S.P.; Jena, S.; Jirden, L.; Jones, G.T.; Jones, P.G.; Jovanovic, P.; Jung, H.; Jung, W.; Jusko, A.; Kalcher, S.; Kalinak, P.; Kalisky, M.; Kalliokoski, T.; Kalweit, A.; Kamermans, R.; Kanaki, K.; Kang, E.; Kang, J.H.; Kaplin, V.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kazantsev, A.; Kebschull, U.; Keidel, R.; Khan, M.M.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, D.J.; Kim, D.S.; Kim, D.W.; Kim, H.N.; Kim, J.H.; Kim, J.S.; Kim, M.; Kim, M.; Kim, S.; Kim, S.H.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Klay, J.L.; Klein, J.; Klein-Bosing, C.; Kliemant, M.; Klovning, A.; Kluge, A.; Knichel, M.L.; Koch, K.; Kohler, M.K.; Kolevatov, R.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Konevskih, A.; Kornas, E.; Kottachchi Kankanamge Don, C.; Kour, R.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kozlov, K.; Kral, J.; Kralik, I.; Kramer, F.; Kraus, I.; Krawutschke, T.; Kretz, M.; Krivda, M.; Krumbhorn, D.; Krus, M.; Kryshen, E.; Krzewicki, M.; Kucheriaev, Y.; Kuhn, C.; Kuijer, P.G.; Kurashvili, P.; Kurepin, A.; Kurepin, A.B.; Kuryakin, A.; Kushpil, S.; Kushpil, V.; Kweon, M.J.; Kwon, Y.; La Rocca, P.; Ladron de Guevara, P.; Lafage, V.; Lara, C.; Larsen, D.T.; Lazzeroni, C.; Le Bornec, Y.; Lea, R.; Lee, K.S.; Lee, S.C.; Lefevre, F.; Lehnert, J.; Leistam, L.; Lenhardt, M.; Lenti, V.; Leon Monzon, I.; Leon Vargas, H.; Levai, P.; Li, X.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M.A.; Liu, L.; Loggins, V.R.; Loginov, V.; Lohn, S.; Lohner, D.; Loizides, C.; Lopez, X.; Lopez Noriega, M.; Lopez Torres, E.; Lovhoiden, G.; Lu, X.G.; Luettig, P.; Lunardon, M.; Luparello, G.; Luquin, L.; Luzzi, C.; Ma, K.; Ma, R.; Madagodahettige-Don, D.M.; Maevskaya, A.; Mager, M.; Mahapatra, D.P.; Maire, A.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Mangotra, L.; Manko, V.; Manso, F.; Manzari, V.; Mao, Y.; Mares, J.; Margagliotti, G.V.; Margotti, A.; Marin, A.; Martashvili, I.; Martinengo, P.; Martinez, M.I.; Martinez Davalos, A.; Martinez Garcia, G.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastromarco, M.; Mastroserio, A.; Matthews, Z.L.; Matyja, A.; Mayani, D.; Mazza, G.; Mazzoni, M.A.; Meddi, F.; Menchaca-Rocha, A.; Mendez Lorenzo, P.; Mercado Perez, J.; Mereu, P.; Miake, Y.; Midori, J.; Milano, L.; Milosevic, J.; Mischke, A.; Miskowiec, D.; Mitu, C.; Mlynarz, J.; Mohanty, B.; Molnar, L.; Montano Zetina, L.; Monteno, M.; Montes, E.; Morando, M.; Moreira De Godoy, D.A.; Moretto, S.; Morsch, A.; Muccifora, V.; Mudnic, E.; Muller, H.; Muhuri, S.; Munhoz, M.G.; Munoz, J.; Musa, L.; Musso, A.; Nandi, B.K.; Nania, R.; Nappi, E.; Nattrass, C.; Navach, F.; Navin, S.; Nayak, T.K.; Nazarenko, S.; Nazarov, G.; Nedosekin, A.; Nendaz, F.; Newby, J.; Nicassio, M.; Nielsen, B.S.; Nikolaev, S.; Nikolic, V.; Nikulin, S.; Nikulin, V.; Nilsen, B.S.; Nilsson, M.S.; Noferini, F.; Nooren, G.; Novitzky, N.; Nyanin, A.; Nyatha, A.; Nygaard, C.; Nystrand, J.; Obayashi, H.; Ochirov, A.; Oeschler, H.; Oh, S.K.; Oleniacz, J.; Oppedisano, C.; Ortiz Velasquez, A.; Ortona, G.; Oskarsson, A.; Ostrowski, P.; Otterlund, I.; Otwinowski, J.; Ovrebekk, G.; Oyama, K.; Ozawa, K.; Pachmayer, Y.; Pachr, M.; Padilla, F.; Pagano, P.; Paic, G.; Painke, F.; Pajares, C.; Pal, S.; Pal, S.K.; Palaha, A.; Palmeri, A.; Pappalardo, G.S.; Park, W.J.; Paticchio, V.; Pavlinov, A.; Pawlak, T.; Peitzmann, T.; Peresunko, D.; Perez Lara, C.E.; Perini, D.; Perrino, D.; Peryt, W.; Pesci, A.; Peskov, V.; Pestov, Y.; Peters, A.J.; Petracek, V.; Petris, M.; Petrov, P.; Petrovici, M.; Petta, C.; Piano, S.; Piccotti, A.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Pitz, N.; Piuz, F.; Piyarathna, D.B.; Platt, R.; Ploskon, M.; Pluta, J.; Pocheptsov, T.; Pochybova, S.; Podesta-Lerma, P.L.M.; Poghosyan, M.G.; Polak, K.; Polichtchouk, B.; Pop, A.; Pospisil, V.; Potukuchi, B.; Prasad, S.K.; Preghenella, R.; Prino, F.; Pruneau, C.A.; Pshenichnov, I.; Puddu, G.; Pulvirenti, A.; Punin, V.; Putis, M.; Putschke, J.; Quercigh, E.; Qvigstad, H.; Rachevski, A.; Rademakers, A.; Rademakers, O.; Radomski, S.; Raiha, T.S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Ramirez Reyes, A.; Rammler, M.; Raniwala, R.; Raniwala, S.; Rasanen, S.S.; Read, K.F.; Real, J.S.; Redlich, K.; Renfordt, R.; Reolon, A.R.; Reshetin, A.; Rettig, F.; Revol, J.P.; Reygers, K.; Ricaud, H.; Riccati, L.; Ricci, R.A.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Rivetti, A.; Rodriguez Cahuantzi, M.; Rohr, D.; Rohrich, D.; Romita, R.; Ronchetti, F.; Rosinsky, P.; Rosnet, P.; Rossegger, S.; Rossi, A.; Roukoutakis, F.; Rousseau, S.; Roy, C.; Roy, P.; Rubio Montero, A.J.; Rui, R.; Rusanov, I.; Ryabinkin, E.; Rybicki, A.; Sadovsky, S.; Safarik, K.; Sahoo, R.; Sahu, P.K.; Saiz, P.; Sakai, S.; Sakata, D.; Salgado, C.A.; Samanta, T.; Sambyal, S.; Samsonov, V.; Sandor, L.; Sandoval, A.; Sano, M.; Sano, S.; Santo, R.; Santoro, R.; Sarkamo, J.; Saturnini, P.; Scapparone, E.; Scarlassara, F.; Scharenberg, R.P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H.R.; Schreiner, S.; Schuchmann, S.; Schukraft, J.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, P.A.; Scott, R.; Segato, G.; Senyukov, S.; Seo, J.; Serci, S.; Serradilla, E.; Sevcenco, A.; Shabratova, G.; Shahoyan, R.; Sharma, N.; Sharma, S.; Shigaki, K.; Shimomura, M.; Shtejer, K.; Sibiriak, Y.; Siciliano, M.; Sicking, E.; Siemiarczuk, T.; Silenzi, A.; Silvermyr, D.; Simonetti, G.; Singaraju, R.; Singh, R.; Sinha, B.C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T.B.; Skjerdal, K.; Smakal, R.; Smirnov, N.; Snellings, R.; Sogaard, C.; Soloviev, A.; Soltz, R.; Son, H.; Song, M.; Soos, C.; Soramel, F.; Spyropoulou-Stassinaki, M.; Srivastava, B.K.; Stachel, J.; Stan, I.; Stefanek, G.; Stefanini, G.; Steinbeck, T.; Stenlund, E.; Steyn, G.; Stocco, D.; Stock, R.; Stolpovskiy, M.; Strmen, P.; Suaide, A.A.P.; Subieta Vasquez, M.A.; Sugitate, T.; Suire, C.; Sumbera, M.; Susa, T.; Swoboda, D.; Symons, T.J.M.; Szanto de Toledo, A.; Szarka, I.; Szostak, A.; Tagridis, C.; Takahashi, J.; J.Tapia Takaki, D.; Tauro, A.; Tavlet, M.; Tejeda Munoz, G.; Telesca, A.; Terrevoli, C.; Thader, J.; Thomas, D.; Thomas, J.H.; Tieulent, R.; Timmins, A.R.; Tlusty, D.; Toia, A.; Torii, H.; Toscano, L.; Tosello, F.; Traczyk, T.; Truesdale, D.; Trzaska, W.H.; Tumkin, A.; Turrisi, R.; Turvey, A.J.; Tveter, T.S.; Ulery, J.; Ullaland, K.; Uras, A.; Urban, J.; Urciuoli, G.M.; Usai, G.L.; Vacchi, A.; Vala, M.; Valencia Palomo, L.; Vallero, S.; van der Kolk, N.; van Leeuwen, M.; Vande Vyvre, P.; Vannucci, L.; Vargas, A.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vechernin, V.; Venaruzzo, M.; Vercellin, E.; Vergara, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Vikhlyantsev, O.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Viyogi, Y.P.; Vodopyanov, A.; Voloshin, K.; Voloshin, S.; Volpe, G.; von Haller, B.; Vranic, D.; Vrlakova, J.; Vulpescu, B.; Wagner, B.; Wagner, V.; Wan, R.; Wang, D.; Wang, Y.; Wang, Y.; Watanabe, K.; Wessels, J.P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, A.; Wilk, G.; Williams, M.C.S.; Windelband, B.; Yang, H.; Yasnopolskiy, S.; Yi, J.; Yin, Z.; Yokoyama, H.; Yoo, I.K.; Yuan, X.; Yushmanov, I.; Zabrodin, E.; Zampolli, C.; Zaporozhets, S.; Zarochentsev, A.; Zavada, P.; Zbroszczyk, H.; Zelnicek, P.; Zenin, A.; Zgura, I.; Zhalov, M.; Zhang, X.; Zhou, D.; Zhu, X.; Zichichi, A.; Zinovjev, G.; Zoccarato, Y.; Zynovyev, M.

2013-07-16

The first measurement of two-pion Bose--Einstein correlations in central PbPb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV at the Large Hadron Collider is presented. We observe a growing trend with energy now not only for the longitudinal and the outward but also for the sideward pion source radius. The pion homogeneity volume and the decoupling time are significantly larger than those measured at RHIC.

The exchange of correlated pions and kaons in the baryon-baryon interaction

International Nuclear Information System (INIS)

Reuber, A.G.

1995-09-01

The exchange of two correlated pions or kaons provides the main part of the intermediate-range attraction between two baryons. In this work, a dynamical model for correlated two-pion and two-kaon exchange in the baryon-baryon interaction is presented, both in the scalar-isoscalar (σ) and the vector-isovector (ρ) channel. The contribution of correlated ππ and K anti K exchange is derived from the amplitudes for the transition of a baryon-antibaryon state (B anti B') to a ππ or K anti K state in the pseudophysical region by applying dispersion theory and unitarity. For the B anti B'→ππ, K anti K amplitudes a microscopic model is constructed, which is based on the hadron-exchange picture. The Born terms include contributions from baryon-exchange as well as ρ-pole diagrams. The correlations between the two pseudoscalar mesons are taken into account exactly by means of ππ-K anti K amplitudes derived likewise from a meson-exchange model, which is in line with the empirical ππ data. The parameters of the B anti B'→ππ, K anti K model, which are related to each other by the assumption of SU(3) symmetry, are determined by the adjustment to the quasiempirical N anti N→ππ amplitudes in the pseudophysical region. It is found that correlated K anti K exchange being negligible in the NN interaction plays an important role in the σ-channel for baryon-baryon states with non-vanishing strangeness. The strength of correlated ππ plus K anti K exchange in the σ-channel decreases with the strangeness of the baryon-baryon system becoming more negative. Due to the admixture of baryon-exchange processes to the SU(3)-symmetric ρ-pole contributions the results for correlated ππ-exchange in the vector-isovector channel deviate from what is expected in the naive SU(3) picture for genuine ρ-exchange. (orig.)

Pion production differential cross section of heavy-ion collisions at subthreshold energies

International Nuclear Information System (INIS)

Abumurad, K.M.

1987-01-01

A revised model for pion production in heavy-ion peripheral collisions at subthreshold energies is presented. The pion-production mechanism investigated here is a two step process involving the formation and subsequent decay of an isobar resonance in the projectile nucleus. The independent-particle shell model with harmonic oscillator states is used to approximate the internal structure of the nucleus. The pion production cross section shows a definite angular distribution characteristic of coherent production. It also gives an indication of the quantum signature of the emitted pions. The results show the disappearance of the quantum signature from the energy spectra because of the inclusion of higher order multipoles. The theory is compared to recent experimental data. The comparison reveals that the general trend is reproduced, which is encouraging

Energy-independent multiple analysis of one-pion photoproduction processes on protons

Energy Technology Data Exchange (ETDEWEB)

Get' man, V.A.; Sanin, V.M.; Telegin, Yu.N.; Shalatskij, S.V. (AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst.)

1983-08-01

For the first time unambiguous estimates are obtained for the multipole photoproduction amplitudes which are based upon the new experimental data on the pion photoproduction on protons combined with the new estiamtes of the ..pi..N-scattering phase shifts. The obtained estimates of the multipole amplitudes are compared with the results of the previous multipole analyses and with the predictions based uoon the dispersion relations.

Pion interferometry of ultra-relativistic hadronic collisions

International Nuclear Information System (INIS)

Kolehmainen, K.

1986-05-01

Pion interferometry of ultra-relativistic hadronic collisions is described in the context of the inside-outside cascade model using a current ensemble method capable of describing an arbitrary distribution of pion sources with an arbitrary velocity distribution. The results are quite distinct from the usual Gaussian and Kopylov parameterizations. Extraction of the temperature parameter, effective source lifetime, and transverse size requires a full three-dimensional analysis of the correlation function in terms of the momentum difference. 7 refs., 4 figs

Pion interferometric tests of transport models

Energy Technology Data Exchange (ETDEWEB)

Padula, S.S.; Gyulassy, M.; Gavin, S. (Lawrence Berkeley Lab., CA (USA). Nuclear Science Div.)

1990-01-08

In hadronic reactions, the usual space-time interpretation of pion interferometry often breaks down due to strong correlations between spatial and momentum coordinates. We derive a general interferometry formula based on the Wigner density formalism that allows for arbitrary phase space and multiparticle correlations. Correction terms due to intermediate state pion cascading are derived using semiclassical hadronic transport theory. Finite wave packets are used to reveal the sensitivity of pion interference effects on the details of the production dynamics. The covariant generalization of the formula is shown to be equivalent to the formula derived via an alternate current ensemble formalism for minimal wave packets and reduces in the nonrelativistic limit to a formula derived by Pratt. The final expression is ideally suited for pion interferometric tests of Monte Carlo transport models. Examples involving gaussian and inside-outside phase space distributions are considered. (orig.).

Pion interferometric tests of transport models

International Nuclear Information System (INIS)

Padula, S.S.; Gyulassy, M.; Gavin, S.

1990-01-01

In hadronic reactions, the usual space-time interpretation of pion interferometry often breaks down due to strong correlations between spatial and momentum coordinates. We derive a general interferometry formula based on the Wigner density formalism that allows for arbitrary phase space and multiparticle correlations. Correction terms due to intermediate state pion cascading are derived using semiclassical hadronic transport theory. Finite wave packets are used to reveal the sensitivity of pion interference effects on the details of the production dynamics. The covariant generalization of the formula is shown to be equivalent to the formula derived via an alternate current ensemble formalism for minimal wave packets and reduces in the nonrelativistic limit to a formula derived by Pratt. The final expression is ideally suited for pion interferometric tests of Monte Carlo transport models. Examples involving gaussian and inside-outside phase space distributions are considered. (orig.)

The intercomparison of the dose distributions between conformation techniques with pions and photons

International Nuclear Information System (INIS)

Karasawa, K.; Nakagawa, K.; Akanuma, A.

1990-01-01

To compare conformation radiation treatment with pions vs photons, dose volume histograms (DVH) to the critical organs, including the spinal cord, kidney, and intestine, were examined in a patient with retroperitoneal soft tissue sarcoma. For photon conformation treatment, the following techniques were used: 360 degree rotation conformation technique (photon conformation), 4 fixed field technique (photon 4-field), and 2-axis conformation technique (photon 2-axial conformation). According to the DVH reduction method, complication probability was estimated. The concave portion of the target was conformed by pion conformation treatment, but not by photon conformation treatment. Pion conformation for the intestine showed the best DVH, whereas photon 4-field technique showed the worst DVH. For the kidney, pion conformation showed better DVH as compared with any other photon conformation treatment technique. In the spinal cord, photon 2-axial conformation was far superior, followed by pion conformation and then photon conformation and 4-field technique. A 2-axial technique showed a bigger inhomogeneity inside the target volume which is critical in curative treatment. TD 50 was 72 Gy for pion conformation, 53 Gy for photon conformation, 51 Gy for photon 4-field, and 68 Gy for photon 2-axial conformation. Complication probabilities for these conformation techniques at 60 Gy were 3%, 85%, 97%, and 9%. In view of tumor control probabilities, pion seems to have the biggest therapeutic ratio among these techniques. (N.K.)

Anisotropy of the pion emission in relativistic nucleus-nucleus collisions

International Nuclear Information System (INIS)

Babinet, R.; Cavata, C.; Demoulins, M.; Fanet, H.; Gosset, J.; Lemaire, M.C.; Le Merdy, A.; L'Hote, D.; Lucas, B.; Poitou, J.; Alard, J.P.; Augerat, J.; Bastid, N.; Charmensat, P.; Dupieux, P.; Fraysse, L.; Marroncle, J.; Montarou, G.; Parizet, M.J.; Ramani, A.; Brochard, F.; Gorodetzky, P.; Racca, C.

1990-01-01

The production of pions and baryons from Ne and Ar induced reactions on Ca, NaF, Nb and Pb targets, in the range of .2 to 1 GeV per nucleon, is discussed. The 4π detector Diogenes at the Saturne accelerator facility is applied. The reaction plane is determined from the baryon momenta distribution and used as a reference for the pion triple differential cross-sections. A transverse momentum analysis is carried out for baryons and pions. The pion squared reduced impact parameter and the flow characteristics are given. The results show that the azimuthal anisotropy of pion emission increases with the asymmetry of the system. The evidence that pion absorption effects may be responsible for the azimuthal anisotropy of the pion emission is provided

Charged pion production from neutron--proton collisions at 790 MeV

International Nuclear Information System (INIS)

Thomas, W.R.

1977-09-01

The two reactions np → nnπ + and np → ppπ - were studied at 790 MeV (incident neutron energy). Pion spectra were measured at 10 different angles with a multiwire proportional chamber spectrometer. Approximately 100,000 events were analyzed. The angular distribution of pions in the np center of momentum system (d sigma/dΩ*) was given by [(123.1 +- 2.7) + (88.3 +- 4.9)cos 2 (theta*)](μb/sr). The cross section sigma(np → NNπ/sup +-/) was determined to be 1.92 +- .20 mb by integrating (d sigma/dΩ*) over all angles. The partial cross section for pion production from T = 0 np interactions (sigma 01 ) was found to be .1/sub -.1//sup +.5/ mb by using the relation sigma 01 = 2sigma(np → NNπ/sup +-)--sigma(pp → ppπ 0 ). Stronger indications of nonresonant pion production were given by the presence of asymmetries between the positive and negative pion spectra and a comparison of the data with an isobar model calculation

Current algebra and soft pion theorems for weak π production

International Nuclear Information System (INIS)

Adler, S.L.

1976-01-01

Beginning with definitions of vector, scalar, axial vector, pseudoscalar, and tensor current densities, equal time current commutators are derived and divergences are discussed. The partially conserved axial current (PCAC) hypothesis is formulated and used to derive the Goldberger--Treiman relation. Current algebra and the PCAC hypothesis are then employed to develop a master formula describing the reaction J + N → π + N where J is a current with four momentum k, and π is a soft pion with four momentum q. Several applications are considered: πN scattering consistency conditions, π isovector electroproduction relations, π production by an isoscalar weak neutral current, π axial vector weak production relations, and low energy theorems which combine soft pion results with knowledge of divergences of the vector or axial vector current J (which induces weak pion production). It is concluded that (1) the entire weak production amplitude is determined to zero order in q by soft pion theorems, and (2) combined relations determine corrections linear in q but of zero order in k

Elastic and inelastic pion reactions on few nucleon systems

International Nuclear Information System (INIS)

Lensky, V.

2007-01-01

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.)

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.)

Possibility of investigation of pion degrees of freedom in atomic nuclei with the help of quasielastic pions knocking out by high energy electrons

CERN Document Server

Neudachin, V G; Sviridova, L L

2002-01-01

The attention is paid to the interesting possibilities of studying the pion degrees of freedom in the atomic nuclei by means of the quasielastic knocking out of pion (e, ep) from the nuclei by the electrons with the energy of several GeV. It appears, that the pulse distribution of the pions, knocked out from the separate nucleons and the nuclei, is in the whole differ essentially different

Tensor polarization in pion-deuteron elastic scattering

International Nuclear Information System (INIS)

Holt, R.J.; Freeman, W.S.; Geesaman, D.F.

1985-01-01

During this year the analysis of measurements of t 20 in π-d elastic scattering was completed and a final summary manuscript was prepared for publication. The results consists of angular distributions of the deuteron tensor polarization in π-d elastic scattering at pion energies of 140, 180, 220 and 256 MeV. Theoretical calculations in which the effects of pion absorption on the elastic channel are small reproduce the data. No rapid angular or energy dependence was found near a pion energy of 134 MeV, where another experiment at SIN has suggested the existence of dibaryon resonances

Two-arm semiconductor spectrometer for charged particles for the investigation of absorption by nuclei of stopped negative pions

International Nuclear Information System (INIS)

Gornov, M.G.; Gurov, Yu.B.; Lukin, A.S.; Morokhov, P.V.; Pechkurov, V.A.; Pichugin, A.P.; Saveliev, V.I.; Shafigullin, R.R.; Sergeev, F.M.; Khomutov, A.A.; Oganesian, K.O.; Osipenko, B.P.; Sandukovsky, V.G.

1984-01-01

A two-arm semiconductor spectrometer for the detection of secondary charged particles, such as p, d, t, 3 He, 4 He and of their correlations in the process of stopped pion absorption by nuclei is described. The spectrometer consists of two telescopes of Si-detectors with a sensitive surface of 800 mm 2 , two semiconductor detectors as monitors and the 'live' target, a silicon surface barrier detector. The number of semiconductor detectors is 19. A technique for pion stop selection in thin targets is described. The problem of particle identification and of measurements of their energy with the help of a multicrystal semiconductor telescope is discussed. The technique provides an absolute normalization of spectra. The 'alive' target helps to obtain more information on the process of pion absorption by Si-nuclei. (orig.)

Multiple-collision model for pion production in relativistic nucleus-nucleus collisions

International Nuclear Information System (INIS)

Vary, J.P.

1978-01-01

A simple model for pion production in relativistic heavy-ion collisions is developed based on nucleon-nucleon data, nuclear density distribution, and the assumption of straight-line trajectories. Multiplicity distributions for total pion production and for negative-pion production are predicted for 40 Ar incident on a Pb 3 O 4 target at 1.8 GeV/nucleon. Production through intermediate baryon resonances reduces the high-multiplicity region but insufficiently to yield agreement with data. This implies the need for a coherent production mechanism

Observations on transverse moments of pions neutral and gamma rays of intermediate mass state ∼3GeW/c2 (MIRIM) in meson multiple production

International Nuclear Information System (INIS)

Fauth, A.C.

1986-01-01

The transverse moment distribution of pions neutral of 32 mirin c-jets with ΣΕγ>20 TeV by tw methods of 2γ->Π 0 coupling. This results independ of any particle production model. A simulation of pion production by Monte Carlo method is carried out and it is shown that, the two methods provide to obtain approximately 50% of correct couplings. The form of pions neutral distribution depends weakly of the percentage of correct couplings. The pions neutral transverse moment distribution of Mirins events is obtained by a third model which is completely independent from the two first, which consists in a composition between an analytical solution and the Monte Carlo method. The results of the three methods are consistents among themselves. (M.C.K.) [pt

Experimental study of the pion-xenon nucleus collisions with-out particle production at 3.5 GeV/c momentum: physical meaning of the proton multiplicity distribution

International Nuclear Information System (INIS)

Strugal'ski, Z.; Pawlak, T.; Pluta, J.

1985-01-01

Distribution of multiplicities of protons emitted in pion-xenon nucleus collisions at 3.5 GeV/c was studied in such events in which incident pion is totally absorbed within the target nucleus without produced particles. The distribution is symmetrical relatively to the proton multiplicity nsub(p)=7.4+-0.3. It is exactly described by binoamial formula, without any fitting, on the basis of an information about the size of the target nucleus and nucleon density distribution in it

Scale of corrections to the t-pole approximation in the quasielastic knockout of pions from nucleon by high energy electrons

CERN Document Server

Neudachin, V G; Yudin, N P

2002-01-01

Investigation of the dominant role of the simplest t-pole diagrams is completed in the processes of pion electroproduction on nucleons at quasielastic knock out kinematics and electron energies of a few GeV. Competition role of pi- and rho-meson t-pole diagrams and s-pole diagram (tree diagram) is regarded. When virtual photon mass is large enough (Q sup 2 >= 2 (GeV/c) sup 2), the latter amplitude is not essential both for longitudinal (d sigma sub L /dt) and for transverse (d sigma sub T /dt) cross sections. At Q sup 2 = 0.7 (GeV/c) sup 2 in the longitudinal cross section the interference term between pion t-pole and s-pole amplitudes is still essential. Vertex functions g subrho sub N sub N (t), obtained from the cross sections of the quasielastic knockout of rho mesons and from cross section of pion photoproduction, are compared. Their discrepancy must give impulse to the development of gauge invariant theory of pion photoproduction

Underlying event background in two-pion correlations in p + p collisions at √ s = 0.9 and 7 TeV

International Nuclear Information System (INIS)

Kisiel, A.

2011-01-01

When analyzing two-particle correlations for identical pions in p + p collisions at √ s = 0.9 and 7 TeV, significant background correlation structures are observed. The structures are also observed for pairs of nonidentical pions and are reproduced by Monte-Carlo simulations. We analyze these structures quantitatively and propose methods to account for their impact on the system sizes extracted from the fits to the identical pion correlation functions

Pion Production Measurement in NA61/SHINE Experiment for High Precision Neutrino Oscillation Experiments

CERN Document Server

Palczewski, Tomasz Jan

2009-01-01

One of physics goals of the NA61/SHINE experiment is a measurement of hadron production cross sections from proton-Carbon interactions at 31GeV/c for the T2K experiment at J-PARC. A precise knowledge of differential cross sections for pion and kaon production is of importance for improving the accuracy of neutrino flux simulations. The NA61 detector has a large angular acceptance, full coverage of the T2K phase space region, and good particle identification. In this work the analyses of negatively charged pion production are presented. Two different methods of negative pion selection and corrections for detector effects are discussed. Finally, preliminary dn/dp distributions of negatively charged pion in p+C interactions at 31 GeV/c are presented.

Measurements of longitudinal and transverse momentum distributions for neutral pions in the forward-rapidity region with the LHCf detector

CERN Document Server

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.

Determination of the pion structure function from muon-pair production

International Nuclear Information System (INIS)

Newman, C.B.; Anderson, K.J.; Coleman, R.N.; Hogan, G.E.; Karhi, K.P.; McDonald, K.T.; Pilcher, J.E.; Rosenberg, E.I.; Sanders, G.H.; Smith, A.J.S.; Thaler, J.J.

1979-01-01

Data on muon-pair production by pions are used to determine the momentum distribution for valence quarks in the pion. The shape of a nucleon structure function is also obtained and is compared with a calculation based on existing data

Practical Calculational Scheme Implementing the Wilsonian RG Results for Nuclear Effective Field Theory Including Pions

International Nuclear Information System (INIS)

Kubo, H.; Harada, K.; Sakaeda, T.; Yamamoto, Y.

2013-01-01

On the basis of the Wilsonian renormalization group (WRG) analysis of nuclear effective field theory (NEFT) including pions, we propose a practical calculational scheme in which the short-distance part of one-pion exchange (S-OPE) is removed and represented as contact terms. The long-distance part of one-pion exchange (L-OPE) is treated as perturbation. The use of dimensional regularization (DR) for diagrams consisting only of contact interactions considerably simplifies the calculation of scattering amplitude and the renormalization group equations. NLO results for nucleon-nucleon elastic scattering in the S-waves are obtained and compared with experiments. A brief comment on NNLO calculations is given. (author)

Two- and three-pion quantum statistics correlations in Pb-Pb collisions at $\\sqrt{s_{NN}}$=2.76 TeV at the CERN Large Hadron Collider

CERN Document Server

Abelev, Betty Bezverkhny; Adamova, Dagmar; Aggarwal, Madan Mohan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agocs, Andras Gabor; Agostinelli, Andrea; Agrawal, Neelima; Ahammed, Zubayer; Ahmad, Nazeer; Ahmad, Arshad; Ahmed, Ijaz; Ahn, Sang Un; Ahn, Sul-Ah; Aimo, Ilaria; Aiola, Salvatore; Ajaz, Muhammad; Akindinov, Alexander; Aleksandrov, Dmitry; Alessandro, Bruno; Alexandre, Didier; Alici, Andrea; Alkin, Anton; Alme, Johan; Alt, Torsten; Altini, Valerio; Altinpinar, Sedat; Altsybeev, Igor; Alves Garcia Prado, Caio; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshaeuser, Harald; Arbor, Nicolas; Arcelli, Silvia; Armesto Perez, Nestor; Arnaldi, Roberta; Aronsson, Tomas; Arsene, Ionut Cristian; Arslandok, Mesut; Augustinus, Andre; Averbeck, Ralf Peter; Awes, Terry; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bagnasco, Stefano; Bailhache, Raphaelle Marie; Bairathi, Vipul; Bala, Renu; Baldisseri, Alberto; Baltasar Dos Santos Pedrosa, Fernando; Ban, Jaroslav; Baral, Rama Chandra; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Ramillien Barret, Valerie; Bartke, Jerzy Gustaw; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batyunya, Boris; Batzing, Paul Christoph; Baumann, Christoph Heinrich; Bearden, Ian Gardner; Beck, Hans; Bedda, Cristina; Behera, Nirbhay Kumar; Belikov, Iouri; Bellini, Francesca; Bellwied, Rene; Belmont Moreno, Ernesto; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Berger, Martin Emanuel; Bergognon, Anais Annick Erica; Bertens, Redmer Alexander; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhati, Ashok Kumar; Bhattacharjee, Buddhadeb; Bhom, Jihyun; Bianchi, Livio; Bianchi, Nicola; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Bjelogrlic, Sandro; Blanco, Fernando; Blau, Dmitry; Blume, Christoph; Bock, Friederike; Boehmer, Felix Valentin; Bogdanov, Alexey; Boggild, Hans; Bogolyubskiy, Mikhail; Boldizsar, Laszlo; Bombara, Marek; Book, Julian Heinz; Borel, Herve; Borissov, Alexander; Bornschein, Joerg; Bossu, Francesco; Botje, Michiel; Botta, Elena; Boettger, Stefan; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Broker, Theo Alexander; Browning, Tyler Allen; Broz, Michal; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Buncic, Predrag; Busch, Oliver; Buthelezi, Edith Zinhle; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Caliva, Alberto; Calvo Villar, Ernesto; Camerini, Paolo; Canoa Roman, Veronica; Carena, Francesco; Carena, Wisla; Carminati, Federico; Casanova Diaz, Amaya Ofelia; Castillo Castellanos, Javier Ernesto; Casula, Ester Anna Rita; Catanescu, Vasile Ioan; Cavicchioli, Costanza; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Chang, Beomsu; Chapeland, Sylvain; Charvet, Jean-Luc Fernand; Chattopadhyay, Subhasis; Chattopadhyay, Sukalyan; Cherney, Michael Gerard; Cheshkov, Cvetan Valeriev; Cheynis, Brigitte; Chibante Barroso, Vasco Miguel; Dobrigkeit Chinellato, David; Chochula, Peter; Chojnacki, Marek; Choudhury, Subikash; Christakoglou, Panagiotis; Christensen, Christian Holm; Christiansen, Peter; Chujo, Tatsuya; Chung, Suh-Urk; Cicalo, Corrado; Cifarelli, Luisa; Cindolo, Federico; Cleymans, Jean Willy Andre; Colamaria, Fabio Filippo; Colella, Domenico; Collu, Alberto; Colocci, Manuel; Conesa Balbastre, Gustavo; Conesa Del Valle, Zaida; Connors, Megan Elizabeth; Contin, Giacomo; Contreras Nuno, Jesus Guillermo; Cormier, Thomas Michael; Corrales Morales, Yasser; Cortese, Pietro; Cortes Maldonado, Ismael; Cosentino, Mauro Rogerio; Costa, Filippo; Crochet, Philippe; Cruz Albino, Rigoberto; Cuautle Flores, Eleazar; Cunqueiro Mendez, Leticia; Dainese, Andrea; Dang, Ruina; Danu, Andrea; Das, Debasish; Das, Indranil; Das, Kushal; Das, Supriya; Dash, Ajay Kumar; Dash, Sadhana; De, Sudipan; Delagrange, Hugues; Deloff, Andrzej; Denes, Ervin Sandor; D'Erasmo, Ginevra; Oliveira Valeriano De Barros, Gabriel; De Caro, Annalisa; De Cataldo, Giacinto; De Cuveland, Jan; De Falco, Alessandro; De Gruttola, Daniele; De Marco, Nora; De Pasquale, Salvatore; De Rooij, Raoul Stefan; Diaz Corchero, Miguel Angel; Dietel, Thomas; Divia, Roberto; Di Bari, Domenico; Di Liberto, Sergio; Di Mauro, Antonio; Di Nezza, Pasquale; Djuvsland, Oeystein; Dobrin, Alexandru Florin; Dobrowolski, Tadeusz Antoni; Domenicis Gimenez, Diogenes; Doenigus, Benjamin; Dordic, Olja; Dorheim, Sverre; Dubey, Anand Kumar; Dubla, Andrea; Ducroux, Laurent; Dupieux, Pascal; Dutt Mazumder, Abhee Kanti; Elia, Domenico; Engel, Heiko; Erazmus, Barbara Ewa; Erdal, Hege Austrheim; Eschweiler, Dominic; Espagnon, Bruno; Estienne, Magali Danielle; Esumi, Shinichi; Evans, David; Evdokimov, Sergey; Eyyubova, Gyulnara; Fabris, Daniela; Faivre, Julien; Falchieri, Davide; Fantoni, Alessandra; Fasel, Markus; Fehlker, Dominik; Feldkamp, Linus; Felea, Daniel; Feliciello, Alessandro; Feofilov, Grigory; Ferencei, Jozef; Fernandez Tellez, Arturo; Gonzalez Ferreiro, Elena; Ferretti, Alessandro; Festanti, Andrea; Figiel, Jan; Araujo Silva Figueredo, Marcel; Filchagin, Sergey; Finogeev, Dmitry; Fionda, Fiorella; Fiore, Enrichetta Maria; Floratos, Emmanouil; Floris, Michele; Foertsch, Siegfried Valentin; Foka, Panagiota; Fokin, Sergey; Fragiacomo, Enrico; Francescon, Andrea; Frankenfeld, Ulrich Michael; Fuchs, Ulrich; Furget, Christophe; Fusco Girard, Mario; Gaardhoeje, Jens Joergen; Gagliardi, Martino; Gallio, Mauro; Gangadharan, Dhevan Raja; Ganoti, Paraskevi; Garabatos Cuadrado, Jose; Garcia-Solis, Edmundo Javier; Gargiulo, Corrado; Garishvili, Irakli; Gerhard, Jochen; Germain, Marie; Gheata, Andrei George; Gheata, Mihaela; Ghidini, Bruno; Ghosh, Premomoy; Ghosh, Sanjay Kumar; Gianotti, Paola; Giubellino, Paolo; Gladysz-Dziadus, Ewa; Glassel, Peter; Gomez Jimenez, Ramon; Gonzalez Zamora, Pedro; Gorbunov, Sergey; Gorlich, Lidia Maria; Gotovac, Sven; Graczykowski, Lukasz Kamil; Grajcarek, Robert; Grelli, Alessandro; Grigoras, Alina Gabriela; Grigoras, Costin; Grigoryev, Vladislav; Grigoryan, Ara; Grigoryan, Smbat; Grynyov, Borys; Grion, Nevio; Grosse-Oetringhaus, Jan Fiete; Grossiord, Jean-Yves; Grosso, Raffaele; Guber, Fedor; Guernane, Rachid; Guerzoni, Barbara; Guilbaud, Maxime Rene Joseph; Gulbrandsen, Kristjan Herlache; Gulkanyan, Hrant; Gunji, Taku; Gupta, Anik; Gupta, Ramni; Khan, Kamal; Haake, Rudiger; Haaland, Oystein Senneset; Hadjidakis, Cynthia Marie; Haiduc, Maria; Hamagaki, Hideki; Hamar, Gergoe; Hanratty, Luke David; Hansen, Alexander; Harris, John William; Hartmann, Helvi; Harton, Austin Vincent; Hatzifotiadou, Despina; Hayashi, Shinichi; Hayrapetyan, Arsen; Heckel, Stefan Thomas; Heide, Markus Ansgar; Helstrup, Haavard; Herghelegiu, Andrei Ionut; Herrera Corral, Gerardo Antonio; Hess, Benjamin Andreas; Hetland, Kristin Fanebust; Hicks, Bernard Richard; Hippolyte, Boris; Hladky, Jan; Hristov, Peter Zahariev; Huang, Meidana; Humanic, Thomas; Hutter, Dirk; Hwang, Dae Sung; Ianigro, Jean-Christophe; Ilkaev, Radiy; Ilkiv, Iryna; Inaba, Motoi; Incani, Elisa; Innocenti, Gian Michele; Ionita, Costin; Ippolitov, Mikhail; Irfan, Muhammad; Ivanov, Marian; Ivanov, Vladimir; Ivanytskyi, Oleksii; Jacholkowski, Adam Wlodzimierz; Jahnke, Cristiane; Jang, Haeng Jin; Janik, Malgorzata Anna; Pahula Hewage, Sandun; Jena, Satyajit; Jimenez Bustamante, Raul Tonatiuh; Jones, Peter Graham; Jung, Hyungtaik; Jusko, Anton; Kalcher, Sebastian; Kalinak, Peter; Kalweit, Alexander Philipp; Kamin, Jason Adrian; Kang, Ju Hwan; Kaplin, Vladimir; Kar, Somnath; Karasu Uysal, Ayben; Karavichev, Oleg; Karavicheva, Tatiana; Karpechev, Evgeny; Kebschull, Udo Wolfgang; Keidel, Ralf; Ketzer, Bernhard Franz; Khan, Mohammed Mohisin; Khan, Palash; Khan, Shuaib Ahmad; Khanzadeev, Alexei; Kharlov, Yury; Kileng, Bjarte; Kim, Beomkyu; Kim, Do Won; Kim, Dong Jo; Kim, Jinsook; Kim, Mimae; Kim, Minwoo; Kim, Se Yong; Kim, Taesoo; Kirsch, Stefan; Kisel, Ivan; Kiselev, Sergey; Kisiel, Adam Ryszard; Kiss, Gabor; Klay, Jennifer Lynn; Klein, Jochen; Klein-Boesing, Christian; Kluge, Alexander; Knichel, Michael Linus; Knospe, Anders Garritt; Kobdaj, Chinorat; Kohler, Markus Konrad; Kollegger, Thorsten; Kolozhvari, Anatoly; Kondratev, Valerii; Kondratyeva, Natalia; Konevskikh, Artem; Kovalenko, Vladimir; Kowalski, Marek; Kox, Serge; Koyithatta Meethaleveedu, Greeshma; Kral, Jiri; Kralik, Ivan; Kramer, Frederick; Kravcakova, Adela; Krelina, Michal; Kretz, Matthias; Krivda, Marian; Krizek, Filip; Krus, Miroslav; Kryshen, Evgeny; Krzewicki, Mikolaj; Kucera, Vit; Kucheryaev, Yury; Kugathasan, Thanushan; Kuhn, Christian Claude; Kuijer, Paulus Gerardus; Kulakov, Igor; Kumar, Jitendra; Kurashvili, Podist; Kurepin, Alexander; Kurepin, Alexey; Kuryakin, Alexey; Kushpil, Svetlana; Kushpil, Vasilij; Kweon, Min Jung; Kwon, Youngil; Ladron De Guevara, Pedro; Lagana Fernandes, Caio; Lakomov, Igor; Langoy, Rune; Lara Martinez, Camilo Ernesto; Lardeux, Antoine Xavier; Lattuca, Alessandra; La Pointe, Sarah Louise; La Rocca, Paola; Lea, Ramona; Lee, Graham Richard; Legrand, Iosif; Lehnert, Joerg Walter; Lemmon, Roy Crawford; Lenhardt, Matthieu Laurent; Lenti, Vito; Leogrande, Emilia; Leoncino, Marco; Leon Monzon, Ildefonso; Levai, Peter; Li, Shuang; Lien, Jorgen Andre; Lietava, Roman; Lindal, Svein; Lindenstruth, Volker; Lippmann, Christian; Lisa, Michael Annan; Ljunggren, Hans Martin; Lodato, Davide Francesco; Lonne, Per-Ivar; Loggins, Vera Renee; Loginov, Vitaly; Lohner, Daniel; Loizides, Constantinos; Lopez, Xavier Bernard; Lopez Torres, Ernesto; Lu, Xianguo; Luettig, Philipp Johannes; Lunardon, Marcello; Luo, Jiebin; Luparello, Grazia; Luzzi, Cinzia; Gago Medina, Alberto Martin; Jacobs, Peter Martin; Ma, Rongrong; Maevskaya, Alla; Mager, Magnus; Mahapatra, Durga Prasad; Maire, Antonin; Malaev, Mikhail; Maldonado Cervantes, Ivonne Alicia; Malinina, Liudmila; Mal'Kevich, Dmitry; Malzacher, Peter; Mamonov, Alexander; Manceau, Loic Henri Antoine; Manko, Vladislav; Manso, Franck; Manzari, Vito; Marchisone, Massimiliano; Mares, Jiri; Margagliotti, Giacomo Vito; Margotti, Anselmo; Marin, Ana Maria; Markert, Christina; Marquard, Marco; Martashvili, Irakli; Martin, Nicole Alice; Martinengo, Paolo; Martinez Hernandez, Mario Ivan; Martinez-Garcia, Gines; Martin Blanco, Javier; Martynov, Yevgen; Mas, Alexis Jean-Michel; Masciocchi, Silvia; Masera, Massimo; Masoni, Alberto; Massacrier, Laure Marie; Mastroserio, Annalisa; Matyja, Adam Tomasz; Mayer, Christoph; Mazer, Joel Anthony; Mazumder, Rakesh; Mazzoni, Alessandra Maria; Meddi, Franco; Menchaca-Rocha, Arturo Alejandro; Mercado-Perez, Jorge; Meres, Michal; Miake, Yasuo; Mikhaylov, Konstantin; Milano, Leonardo; Milosevic, Jovan; Mischke, Andre; Mishra, Aditya Nath; Miskowiec, Dariusz Czeslaw; Mitu, Ciprian Mihai; Mlynarz, Jocelyn; Mohanty, Bedangadas; Molnar, Levente; Montano Zetina, Luis Manuel; Montes Prado, Esther; Morando, Maurizio; Moreira De Godoy, Denise Aparecida; Moretto, Sandra; Morreale, Astrid; Morsch, Andreas; Muccifora, Valeria; Mudnic, Eugen; Muhuri, Sanjib; Mukherjee, Maitreyee; Muller, Hans; Gameiro Munhoz, Marcelo; Murray, Sean; Musa, Luciano; Musinsky, Jan; Nandi, Basanta Kumar; Nania, Rosario; Nappi, Eugenio; Nattrass, Christine; Nayak, Tapan Kumar; Nazarenko, Sergey; Nedosekin, Alexander; Nicassio, Maria; Niculescu, Mihai; Nielsen, Borge Svane; Nikolaev, Sergey; Nikulin, Sergey; Nikulin, Vladimir; Nilsen, Bjorn Steven; Noferini, Francesco; Nomokonov, Petr; Nooren, Gerardus; Nyanin, Alexander; Nyatha, Anitha; Nystrand, Joakim Ingemar; Oeschler, Helmut Oskar; Oh, Saehanseul; Oh, Sun Kun; Okatan, Ali; Olah, Laszlo; Oleniacz, Janusz; Oliveira Da Silva, Antonio Carlos; Onderwaater, Jacobus; Oppedisano, Chiara; Ortiz Velasquez, Antonio; Oskarsson, Anders Nils Erik; Otwinowski, Jacek Tomasz; Oyama, Ken; Pachmayer, Yvonne Chiara; Pachr, Milos; Pagano, Paola; Paic, Guy; Painke, Florian; Pajares Vales, Carlos; Pal, Susanta Kumar; Palmeri, Armando; Pant, Divyash; Papikyan, Vardanush; Pappalardo, Giuseppe; Park, Woojin; Passfeld, Annika; Patalakha, Dmitry; Paticchio, Vincenzo; Paul, Biswarup; Pawlak, Tomasz Jan; Peitzmann, Thomas; Pereira Da Costa, Hugo Denis Antonio; Pereira De Oliveira Filho, Elienos; Peresunko, Dmitry Yurevich; Perez Lara, Carlos Eugenio; Peryt, Wiktor Stanislaw; Pesci, Alessandro; Pestov, Yury; Petracek, Vojtech; Petran, Michal; Petris, Mariana; Petrovici, Mihai; Petta, Catia; Piano, Stefano; Pikna, Miroslav; Pillot, Philippe; Pinazza, Ombretta; Pinsky, Lawrence; Piyarathna, Danthasinghe; Planinic, Mirko; Ploskon, Mateusz Andrzej; Pluta, Jan Marian; Pochybova, Sona; Podesta Lerma, Pedro Luis Manuel; Poghosyan, Martin; Pohjoisaho, Esko Heikki Oskari; Polishchuk, Boris; Poljak, Nikola; Pop, Amalia; Porteboeuf, Sarah Julie; Porter, R Jefferson; Pospisil, Vladimir; Potukuchi, Baba; Prasad, Sidharth Kumar; Preghenella, Roberto; Prino, Francesco; Pruneau, Claude Andre; Pshenichnov, Igor; Puddu, Giovanna; Pujahari, Prabhat Ranjan; Punin, Valery; Putschke, Jorn Henning; Qvigstad, Henrik; Rachevski, Alexandre; Raha, Sibaji; Rak, Jan; Rakotozafindrabe, Andry Malala; Ramello, Luciano; Raniwala, Rashmi; Raniwala, Sudhir; Rasanen, Sami Sakari; Rascanu, Bogdan Theodor; Rathee, Deepika; Rauf, Aamer Wali; Razazi, Vahedeh; Read, Kenneth Francis; Real, Jean-Sebastien; Redlich, Krzysztof; Reed, Rosi Jan; Rehman, Attiq Ur; Reichelt, Patrick Simon; Reicher, Martijn; Reidt, Felix; Renfordt, Rainer Arno Ernst; Reolon, Anna Rita; Reshetin, Andrey; Rettig, Felix Vincenz; Revol, Jean-Pierre; Reygers, Klaus Johannes; Riabov, Viktor; Ricci, Renato Angelo; Richert, Tuva Ora Herenui; Richter, Matthias Rudolph; Riedler, Petra; Riegler, Werner; Riggi, Francesco; Rivetti, Angelo; Rocco, Elena; Rodriguez Cahuantzi, Mario; Rodriguez Manso, Alis; Roeed, Ketil; Rogochaya, Elena; Sharma, Rohni; Rohr, David Michael; Roehrich, Dieter; Romita, Rosa; Ronchetti, Federico; Ronflette, Lucile; Rosnet, Philippe; Rossegger, Stefan; Rossi, Andrea; Roy, Ankhi; Roy, Christelle Sophie; Roy, Pradip Kumar; Rubio Montero, Antonio Juan; Rui, Rinaldo; Russo, Riccardo; Ryabinkin, Evgeny; Ryabov, Yury; Rybicki, Andrzej; Sadovskiy, Sergey; Safarik, Karel; Sahlmuller, Baldo; Sahoo, Raghunath; Sahu, Pradip Kumar; Saini, Jogender; Salgado Lopez, Carlos Alberto; Salzwedel, Jai Samuel Nielsen; Sambyal, Sanjeev Singh; Samsonov, Vladimir; Sanchez Castro, Xitzel; Sanchez Rodriguez, Fernando Javier; Sandor, Ladislav; Sandoval, Andres; Sano, Masato; Santagati, Gianluca; Sarkar, Debojit; Scapparone, Eugenio; Scarlassara, Fernando; Scharenberg, Rolf Paul; Schiaua, Claudiu Cornel; Schicker, Rainer Martin; Schmidt, Christian Joachim; Schmidt, Hans Rudolf; Schuchmann, Simone; Schukraft, Jurgen; Schulc, Martin; Schuster, Tim Robin; Schutz, Yves Roland; Schwarz, Kilian Eberhard; Schweda, Kai Oliver; Scioli, Gilda; Scomparin, Enrico; Scott, Patrick Aaron; Scott, Rebecca Michelle; Segato, Gianfranco; Seger, Janet Elizabeth; Selyuzhenkov, Ilya; Seo, Jeewon; Serradilla Rodriguez, Eulogio; Sevcenco, Adrian; Shabetai, Alexandre; Shabratova, Galina; Shahoyan, Ruben; Shangaraev, Artem; Sharma, Natasha; Sharma, Satish; Shigaki, Kenta; Shtejer Diaz, Katherin; Sibiryak, Yury; Siddhanta, Sabyasachi; Siemiarczuk, Teodor; Silvermyr, David Olle Rickard; Silvestre, Catherine Micaela; Simatovic, Goran; Singaraju, Rama Narayana; Singh, Ranbir; Singha, Subhash; Singhal, Vikas; Sinha, Bikash; Sarkar - Sinha, Tinku; Sitar, Branislav; Sitta, Mario; Skaali, Bernhard; Skjerdal, Kyrre; Smakal, Radek; Smirnov, Nikolai; Snellings, Raimond; Soegaard, Carsten; Soltz, Ron Ariel; Song, Jihye; Song, Myunggeun; Soramel, Francesca; Sorensen, Soren Pontoppidan; Spacek, Michal; Sputowska, Iwona Anna; Spyropoulou-Stassinaki, Martha; Srivastava, Brijesh Kumar; Stachel, Johanna; Stan, Ionel; Stefanek, Grzegorz; Steinpreis, Matthew Donald; Stenlund, Evert Anders; Steyn, Gideon Francois; Stiller, Johannes Hendrik; Stocco, Diego; Stolpovskiy, Mikhail; Strmen, Peter; Alarcon Do Passo Suaide, Alexandre; Subieta Vasquez, Martin Alfonso; Sugitate, Toru; Suire, Christophe Pierre; Suleymanov, Mais Kazim Oglu; Sultanov, Rishat; Sumbera, Michal; Susa, Tatjana; Symons, Timothy; Szanto De Toledo, Alejandro; Szarka, Imrich; Szczepankiewicz, Adam; Szymanski, Maciej Pawel; Takahashi, Jun; Tangaro, Marco-Antonio; Tapia Takaki, Daniel Jesus; Tarantola Peloni, Attilio; Tarazona Martinez, Alfonso; Tauro, Arturo; Tejeda Munoz, Guillermo; Telesca, Adriana; Terrevoli, Cristina; Ter-Minasyan, Astkhik; Thaeder, Jochen Mathias; Thomas, Deepa; Tieulent, Raphael Noel; Timmins, Anthony Robert; Toia, Alberica; Torii, Hisayuki; Trubnikov, Victor; Trzaska, Wladyslaw Henryk; Tsuji, Tomoya; Tumkin, Alexandr; Turrisi, Rosario; Tveter, Trine Spedstad; Ulery, Jason Glyndwr; Ullaland, Kjetil; Ulrich, Jochen; Uras, Antonio; Usai, Gianluca; Vajzer, Michal; Vala, Martin; Valencia Palomo, Lizardo; Vallero, Sara; Vande Vyvre, Pierre; Vannucci, Luigi; Van Hoorne, Jacobus Willem; Van Leeuwen, Marco; Diozcora Vargas Trevino, Aurora; Varma, Raghava; Vasileiou, Maria; Vasiliev, Andrey; Vechernin, Vladimir; Veldhoen, Misha; Venaruzzo, Massimo; Vercellin, Ermanno; Vergara Limon, Sergio; Vernet, Renaud; Verweij, Marta; Vickovic, Linda; Viesti, Giuseppe; Viinikainen, Jussi Samuli; Vilakazi, Zabulon; Villalobos Baillie, Orlando; Vinogradov, Alexander; Vinogradov, Leonid; Vinogradov, Yury; Virgili, Tiziano; Viyogi, Yogendra; Vodopyanov, Alexander; Volkl, Martin Andreas; Voloshin, Kirill; Voloshin, Sergey; Volpe, Giacomo; Von Haller, Barthelemy; Vorobyev, Ivan; Vranic, Danilo; Vrlakova, Janka; Vulpescu, Bogdan; Vyushin, Alexey; Wagner, Boris; Wagner, Jan; Wagner, Vladimir; Wang, Mengliang; Wang, Yifei; Watanabe, Daisuke; Weber, Michael; Wessels, Johannes Peter; Westerhoff, Uwe; Wiechula, Jens; Wikne, Jon; Wilde, Martin Rudolf; Wilk, Grzegorz Andrzej; Wilkinson, Jeremy John; Williams, Crispin; Windelband, Bernd Stefan; Winn, Michael Andreas; Xiang, Changzhou; Yaldo, Chris G; Yamaguchi, Yorito; Yang, Hongyan; Yang, Ping; Yang, Shiming; Yano, Satoshi; Yasnopolskiy, Stanislav; Yi, Jungyu; Yin, Zhongbao; Yoo, In-Kwon; Yushmanov, Igor; Zaccolo, Valentina; Zach, Cenek; Zaman, Ali; Zampolli, Chiara; Zaporozhets, Sergey; Zarochentsev, Andrey; Zavada, Petr; Zavyalov, Nikolay; Zbroszczyk, Hanna Paulina; Zgura, Sorin Ion; Zhalov, Mikhail; Zhang, Fan; Zhang, Haitao; Zhang, Xiaoming; Zhang, Yonghong; Zhao, Chengxin; Zhou, Daicui; Zhou, Fengchu; Zhou, You; Zhu, Hongsheng; Zhu, Jianhui; Zhu, Jianlin; Zhu, Xiangrong; Zichichi, Antonino; Zimmermann, Alice; Zimmermann, Markus Bernhard; Zinovjev, Gennady; Zoccarato, Yannick Denis; Zynovyev, Mykhaylo; Zyzak, Maksym

2014-02-26

Correlations induced by quantum statistics are sensitive to the spatio-temporal extent as well as dynamics of particle emitting sources in heavy-ion collisions. In addition, such correlations can be used to search for the presence of a coherent component of pion production. Two and three-pion correlations of same and mixed-charge are measured at low relative momentum to estimate the coherent fraction of charged pions in Pb-Pb collisions at $\\sqrt{s_{NN}}$= 2.76 TeV at the LHC with ALICE. The genuine three-pion quantum statistics correlation is found to be suppressed relative to the two-pion correlation based on the assumption of fully chaotic pion emission.The suppression is observed to decrease with triplet momentum. The observed suppression at low triplet momentum may correspond to a coherent fraction in charged pion emission of 22% +- 12%.

Galileo-invariant theory of low energy pion-nucleus scattering

International Nuclear Information System (INIS)

Mach, R.

1980-01-01

Two classes of Galileo-invariant optical models are constructed for pion elastic scattering by nuclei. The first, the two-body model, has been obtained assuming that the pion-bound nucleon dynamics is determined by the pion-nucleon kinetic energy. In deriving the second model, the (A+1)-body dynamics has been taken into account. The technique of effective nucleon momenta maintains the nonlocal propagation of the pion-target nucleon subsystem through the nucleus in contrast with the standard static approximation

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.

Optimisation of amplitude distribution of magnetic Barkhausen noise

Science.gov (United States)

Pal'a, Jozef; Jančárik, Vladimír

2017-09-01

The magnetic Barkhausen noise (MBN) measurement method is a widely used non-destructive evaluation technique used for inspection of ferromagnetic materials. Besides other influences, the excitation yoke lift-off is a significant issue of this method deteriorating the measurement accuracy. In this paper, the lift-off effect is analysed mainly on grain oriented Fe-3%Si steel subjected to various heat treatment conditions. Based on investigation of relationship between the amplitude distribution of MBN and lift-off, an approach to suppress the lift-off effect is proposed. Proposed approach utilizes the digital feedback optimising the measurement based on the amplitude distribution of MBN. The results demonstrated that the approach can highly suppress the lift-off effect up to 2 mm.

Neural network and parton two fireball model for pseudo-rapidity distribution in proton-proton collision

International Nuclear Information System (INIS)

El-Bakry, M.Y.

2000-01-01

Pseudo-Rapidity distribution of created pions from proton-proton (p-p) interaction has been studied in the framework of artificial neural network (ANN) and the parton two fireball model (PTFM). The predicted distributions from the ANN based model and the parton two fireball model is compared with the corresponding experimental results. The ANN model has proved better matching for experimental data specially at high energies where the conventional two fireball model representation deteriorates

PIPIT: a momentum space optical potential code for pions

Energy Technology Data Exchange (ETDEWEB)

Eisenstein, R A [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics; Tabakin, F [Pittsburgh Univ., Pa. (USA). Dept. of Physics

1976-11-01

Angular distributions for the elastic scattering of pions are generated by summing a partial wave series. The elastic T-matrix elements for each partial wave are obtained by solving a relativistic Lippmann-Schwinger equation in momentum space using a matrix inversion technique. Basically the Coulomb interaction is included exactly using the method of Vincent and Phatak. The ..pi..N amplitude is obtained from phase shift information on-shell and incorporates a separable off-shell form factor to ensure a physically reasonable off-shell extrapolation. The ..pi..N interaction is of finite range and a kinematic transformation procedure is used to express the ..pi..N amplitude in the ..pi.. nucleus frame. A maximum of 30 partial waves can be used in the present version of the program to calculate the cross section. The Lippmann-Schwinger equation is presently solved for each partial wave by inverting a 34x34 supermatrix. At very high energies, larger dimensions may be required. The present version of the code uses a separable non-local ..pi..N potential of finite range; other types of non-localities, or non-separable potentials, may be of physical interest.

Higher-Twist Distribution Amplitudes of the K Meson in QCD

CERN Document Server

Ball, P; Lenz, A; Ball, Patricia

2006-01-01

We present a systematic study of twist-3 and twist-4 light-cone distribution amplitudes of the K meson in QCD. The structure of SU(3)-breaking corrections is studied in detail. Non-perturbative input parameters are estimated from QCD sum rules and renormalons. As a by-product, we give a complete reanalysis of the twist-3 and -4 parameters of the pi-meson distribution amplitudes; some of the results differ from those usually quoted in the literature.

Low energy pion--nucleon and pion--deuteron interactions

International Nuclear Information System (INIS)

Burman, R.L.

1975-01-01

This survey concentrates upon current experiments in the fields of pion-nucleon and pion-deuteron interactions, for low-energy incident pions--below 300 MeV. The discussion is restricted to very recent work. The topics to be covered are: π +- p → π +- p, Elastic Scattering; π +- p → π +- pγ, Bremsstrahlung; π + d → pp, Absorption; π d → π + d, Elastic Scattering; and π + d → π + pn, Breakup. (14 figures) (U.S.)

Renormalization of three-quark operators for baryon distribution amplitudes

Energy Technology Data Exchange (ETDEWEB)

Gruber, Michael

2017-07-01

In this thesis we design and study three-quark operators that are essential for the calculation of baryon distribution amplitudes. These nonperturbative objects grant insight into the internal structure of hadrons, but their renormalization patterns are nontrivial and need to be treated with care. With the application to lattice simulations in mind we discuss two renormalization schemes, MS and RI{sup '}/SMOM, and connect them by calculating conversion factors. Armed with this knowledge we are able to extract phenomenologically relevant results from an accompanying lattice analysis.

Renormalization of three-quark operators for baryon distribution amplitudes

International Nuclear Information System (INIS)

Gruber, Michael

2017-01-01

In this thesis we design and study three-quark operators that are essential for the calculation of baryon distribution amplitudes. These nonperturbative objects grant insight into the internal structure of hadrons, but their renormalization patterns are nontrivial and need to be treated with care. With the application to lattice simulations in mind we discuss two renormalization schemes, MS and RI ' /SMOM, and connect them by calculating conversion factors. Armed with this knowledge we are able to extract phenomenologically relevant results from an accompanying lattice analysis.

Subthreshold Production of Neutral Pions in Heavy Ion Collisions

CERN Multimedia

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...

Longitudinal Electroproduction of Charged Pions from

International Nuclear Information System (INIS)

David Gaskell; Abdellah Ahmidouch; Pawel Ambrozewicz; H. Anklin; John Arrington; K. Assamagan; Steven Avery; Kevin Bailey; Oliver K. Baker; Shelton Beedoe; Elizabeth Beise; Herbert Breuer; D. S. Brown; Roger Carlini; Jinseok Cha; Nicholas Chant; Anthony Cowley; Samuel Danagoulian; D. De Schepper; Jim Dunne; Dipangkar Dutta; Rolf Ent; Liping Gan; Ashot Gasparian; Donald Geesaman; Ron Gilman; Charles Glashausser; Paul Gueye; M. Harvey; O. Hashimoto; Wendy Hinton; G. Hofman; Ceasar Jackson; Hal Jackson; Cynthia Keppel; Ed Kinney; Doug Koltenuk; G. Kyle; Allison Lung; David Mack; D. McKee; Joseph Mitchell; Hamlet Mkrtchyan; B. Mueller; Gabriel Niculescu; Ioana Niculescu; Tom O'Neill; V. Papavassiliou; Dave Potterveld; Juerg Reinhold; Philip Roos; Reyad Sawafta; Ralph Segel; Stepan Stepanyan; Vardan Tadevosyan; T. Takahashi; Liguang Tang; B. Terburg; D. Van Westrum; J. Volmer; T. P. Welch; Stephen Wood; Lulin Yuan; Ben Zeidman; Beni Zihlmann

2001-01-01

Separated longitudinal and transverse cross sections for charged pion electroproduction from 1 H, 2 H, and 3 He were measured at Q 2 = 0.4 (GeV/c) 2 for two values of the invariant mass, (bar W) = 1.15 GeV and (bar W) = 1.60 GeV, in a search for a mass dependence which would signal the effect of nuclear pions. This is the first such study that includes recoil momenta significantly above the Fermi surface. The longitudinal cross section, if dominated by the pion-pole process, should be sensitive to nuclear pion currents. Comparisons of the longitudinal cross section target ratios to a quasifree calculation reveal a significant suppression in 3> He at (bar W) = 1.60 GeV. The (bar W) = 1.15 GeV results are consistent with simple estimates of the effect of nuclear pion currents, but are also consistent with pure quasifree production

Quantum signature in heavy-ion pion production

International Nuclear Information System (INIS)

Buvel, R.L.

1985-01-01

A revised model for pion production in heavy-ion peripheral collisions is presented. The pion-production mechanism investigated here is a two step process involving the formation and subsequent decay of an isobar resonance in the projectile nucleus. The independent-particle shell model with harmonic oscillator states is used to approximate the internal structure of the nucleus. The inclusion of the internal structure of the projectile nucleus led to the discovery of a quantum signature in the pion-production differential cross section. The quantum signature involves a matching condition where the pion-production differential cross section goes to zero for a particular value of the pion kinetic energy. The theory is compared to a recent experiment, but the results of this comparison are inconclusive

Study of the isospin properties of single-pion production by neutrinos

International Nuclear Information System (INIS)

Barnes, V.E.; Carmony, D.D.; Garfinkel, A.F.

1978-01-01

Results are presented on the three single-pion production reactions νP-μ - Pπ + , νn-μ - nπ + , and νn-μ - Pπ 0 . Measurements were made from threshold to a neutrino energy of 1.5 GeV using the Argonne National Laboratory 12-foot bubble chamber filled with deuterium and exposed to a broad band neutrino beam. In addition to a resonant isospin I = 3/2 N/sub π/ amplitude, a large I = 1/2 amplitude was found as predicted by Adler

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 condensation and instabilities: current theory and experiment

International Nuclear Information System (INIS)

Gyulassy, M.

1980-05-01

Current calculations of pion condensation phenomena in symmetric nuclear matter are reviewed. The RPA and MFA methods are compared. Latest results [LBL-10572] with a relativistic MFA theory constrained by bulk nuclear properties are presented. The differences between equilibrium (condensation) and nonequilibrium (dynamic) instabilities are discussed. Finally, two-proton correlation experiments aimed at looking for critical scattering phenomena and two-pion correlation experiments aimed at looking for pion field coherence are analyzed. 10 figures, 2 tables

Determination of the pion and kaon structure functions

International Nuclear Information System (INIS)

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.

1980-01-01

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 π/=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

Galileo-invariant theory of low energy pion-nucleus scattering. II

International Nuclear Information System (INIS)

Mach, R.

1983-01-01

Two classes of Galileo-invariant optical models are constructed for pion elastic scattering by nuclei. The former, the two-body model, was obtained assuming that the pion-bound nucleon dynamics is determined by the pion-nucleon kinetic energy. In deriving the latter model, the (A+1)-body dynamics was taken into account. The technique of effective nucleon momenta maintains the nonlocal propagation of the pion-target nucleon subsystem through the nucleus in contrast with the standard static approximation. (author)

Nucleon multiplicities after pion absorption in 160

International Nuclear Information System (INIS)

Hamers, R.

1989-01-01

The experiment described in this thesis concerns a simultaneous measurement of two- and higher-fold coincidences following positive and negative pion absorption in 16 0. The detected particles are protons, neutrons and deuterons. The detection and analysis of charged particles is discussed. The incident pion energy was 65 MeV, thus well below the delta resonance. The low pion energy was 65 MeV, thus well below the delta resonance. The low pion energy ensures that contributions of initial state interactions, i.e. pion-nucleon scattering preceding absorption, are minimized. The following reaction channels were selected and analyzed: π + ,pp), (π + ,pd). Evidence for quasifree reaction precessed has been investigated by comparing the data with phase-space calculations incorporating the geometry of the experimental setup. (author). 36 refs.; 1 figs.; 3 tabs

Δ effects in pion-nucleon scattering and the strength of the two-pion-exchange three-nucleon interaction

International Nuclear Information System (INIS)

Pandharipande, V.R.; Phillips, D.R.; Kolck, U. van

2005-01-01

We consider the relationship between p-wave πN scattering and the strength of the p-wave two-pion-exchange three-nucleon interaction (TPE3NI). We explain why effective theories that do not contain the Delta resonance as an explicit degree of freedom tend to overestimate the strength of the TPE3NI. The overestimation can be remedied by higher-order terms in these 'Delta-less' theories, but such terms are not yet included in state-of-the-art chiral effective field theory calculations of the nuclear force. This suggests that these calculations can predict the strength of the TPE3NI only to an accuracy of ±25%

A phenomenological determination of the pion-nucleon scattering lengths from pionic hydrogen

CERN Document Server

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).

Short range correlations in the pion s-wave self-energy of pionic atoms

OpenAIRE

Salcedo, L. L.; Holinde, K.; Oset, E.; Schütz, C.

1995-01-01

We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave $\\pi N$ amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one. In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together lowest order, Pauli corrected ...

Measurement of the charged-pion polarisability at COMPASS

CERN Multimedia

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.

Inclusive particle production at forward angles from collisions of light relativistic nuclei: Negative pions

International Nuclear Information System (INIS)

Moeller, E.; Anderson, L.; Brueckner, W.; Nagamiya, S.; Nissen-Meyer, S.; Schroeder, L.; Shapiro, G.; Steiner, H.

1983-01-01

We have measured single particle inclusive spectra of negative pions produced at angles from 0 0 to 12 0 (lab) in collisions of 1.05 and 2.1 GeV/nucleon protons, deuterons, alpha particles, and carbon nuclei with targets of C, Cu, Pb, and H (from a CH 2 -C subtraction). Most of the pions are produced in the kinematical domains allowed in free nucleon-nucleon collisions, but for alpha and carbon projectiles we have also observed pions whose energies range up to nearly twice the kinetic energy of a nucleon in the projectile. Our results suggest that processes involving more than two colliding nucleons and/or high internal momentum components are involved in the production of these high energy pions. Comparison is made with several hypotheses of scaling including specific dynamical models, and some disagreement is observed. We present fits to the kinetic energy dependence of the data, and the target and projectile mass dependence. We also show transverse momentum distributions

Virtual photons in the pion form factors and the energy-momentum tensor

Energy Technology Data Exchange (ETDEWEB)

Kubis, Bastian E-mail: b.kubis@fz-juelich.de; Meissner, Ulf-G. E-mail: ulf-g.meissner@fz-juelich.de

2000-05-22

We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector as well as the charged pion scalar form factor. The scalar radius of the neutral pion is reduced by two percent. We perform infrared regularization by considering electron-positron annihilation into pions and the decay of a light Higgs boson into a pion pair. We discuss the detector resolution dependent contributions to the various form factors and pion radii.

Virtual photons in the pion form factors and the energy-momentum tensor

International Nuclear Information System (INIS)

Kubis, Bastian; Meissner, Ulf-G.

2000-01-01

We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next-to-leading order in two-flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy-momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector as well as the charged pion scalar form factor. The scalar radius of the neutral pion is reduced by two percent. We perform infrared regularization by considering electron-positron annihilation into pions and the decay of a light Higgs boson into a pion pair. We discuss the detector resolution dependent contributions to the various form factors and pion radii

Two-pion Bose-Einstein correlations in pp collisions at sqrt(s)=900 GeV

NARCIS (Netherlands)

Aamodt, K.; Chojnacki, M.; Christakoglou, P.; de Rooij, R. S.; Grelli, A.; Ivan, C.G.; Kamermans, R.; Mischke, A.; Nooren, G.J.L.; Peitzmann, T.; Simili, E.; van Leeuwen, M.; Verweij, M.

2010-01-01

We report on the measurement of two-pion correlation functions from pp collisions at square(s)=900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the Hanbury Brown–Twiss radius with increasing event multiplicity, in line with other measurements

Can we get deeper inside the pion at the LHC?

Energy Technology Data Exchange (ETDEWEB)

Petrov, V.A.; Ryutin, R.A.; Sobol, A.E. [Institute for High Energy Physics, Protvino (Russian Federation); Murray, M.J. [University of Kansas, Kansas City, KS (United States)

2012-02-15

We propose a measurement of leading neutrons spectra at LHC in order to extract inclusive {pi}{sup +} p and {pi}{sup +}{pi} {sup +} cross-sections with high p{sub T} jets production. The cross-sections for these processes are simulated with the use of parton distributions in hadrons. In this work we estimate the possibility to extract parton distributions in the pion from the data on these cross-sections and also search for signatures of fundamental differences in the pion and proton structure. (orig.)

An improved optical potential for low-energy pion-nucleus scattering

International Nuclear Information System (INIS)

Khankhasaev, M.Kh.; Topil'skaya, N.S.

1988-01-01

A new procedure for calculating the imaginary part the of Stricker, McManus and Carr (SMC) optical potential is proposed. It is based on an approximate expression for the pion-nucleon scattering amplitude including nuclear structure effects. It is shown that the resulting potential with the absorption parameters fitted to the pionic atom data provides a good description of the scattering up to 50 MeV

Pion double charge exchange and nuclear structure

International Nuclear Information System (INIS)

Ginocchio, J.N.

1987-01-01

Pion double charge exchange to both the double-analog state and the ground state is studied for medium weight nuclei. The relative cross section of these two transitions and the importance of nuclear structure as a function of pion kinetic energy is examined. 16 figs., 5 tabs

Coherent production of two and three pions in pd reactions at 19 GeV/c

International Nuclear Information System (INIS)

Bakken, V.; Gennow, H.; Lundborg, P.; Maekelae, J.; Moellerud, R.; Pimiae, M.; Sellden, B.; Sundell, E.; Tuominemi, J.K.

1976-10-01

The coherent reactions pd→pdπ + π - , pd→pdπ + π - π 0 and pd→ndπ + π + π - are studied. In the two first reactions strong production of Δ ++ (1236) is observed. Production of d* 0 and d* + is observed in the first and second reactions respectively. The forward slope of the t-distribution of the pπ + π - system in the pd→pdπ + π - channel decreases with increasing mass. The 1500 and 1700 MeV enhancements in the pπ + π - mass spectrum of this channel are studied. Assuming that the Gribov-Morrison rule holds, it is found that by analysing the moments of the decay angular distributions that the resonances N(1470), N(1520) and N(1688) are the most likely resonances to be identified with these enhancements. Evidence is found against s-channel helicity conservation and some evidence against t-channel helicity conservation. The decay parameters of the Δ ++ (1236) in the reaction pd→Δ ++ π - d are in good agreement with the predictions of a one-pion exchange model. (Auth.)

Iterative structure within the five-particle two-loop amplitude

International Nuclear Information System (INIS)

Cachazo, Freddy; Spradlin, Marcus; Volovich, Anastasia

2006-01-01

We find an unexpected iterative structure within the two-loop five-gluon amplitude in N=4 supersymmetric Yang-Mills theory. Specifically, we show that a subset of diagrams contributing to the full amplitude, including a two-loop pentagon-box integral with nontrivial dependence on five kinematical variables, satisfies an iterative relation in terms of one-loop scalar box diagrams. The implications of this result for the possible iterative structure of the full two-loop amplitude are discussed

Self-consistent theory of hadron-nucleus scattering. Application to pion physics

International Nuclear Information System (INIS)

Johnson, M.B.

1980-01-01

The requirement of using self-consistent amplitudes to evaluate microscopically the scattering of strongly interacting particles from nuclei is developed. Application of the idea to a simple model of pion-nucleus scattering is made. Numerical results indicate that the expansion of the optical potential converges when evaluated in terms of fully self-consistent quantities. A comparison of the results to a recent determination of the spreading interaction in the phenomenological isobar-hole model shows that the theory accounts for the sign and magnitude of the real and imaginary part of the spreading interaction with no adjusted parameters. The self-consistnt theory has a strong density dependence, and the consequences of this for pion-nucleus scattering are discussed. 18 figures, 1 table

The pion form factor from lattice QCD with two dynamical flavours

Energy Technology Data Exchange (ETDEWEB)

Broemmel, D. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie]|[Regensburg Univ. (Germany). Inst. fuer Physik 1 - Theoretische Physik; Diehl, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie; Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Physik 1 - Theoretische Physik] (and others)

2006-08-15

We compute the electromagnetic form factor of the pion using non-perturbatively O(a) improved Wilson fermions. The calculations are done for pion masses down to 400 MeV and for lattice spacings of 0.07-0.11 fm. We check for finite size effects by repeating some of the measurements on smaller lattices. The large number of lattice parameters we use allows us to extrapolate to the physical point. For the square of the charge radius we find left angle r{sup 2} right angle =0.440(19) fm{sup 2}, in good agreement with experiment. (orig.)

The PIOTRON: initial performance, preparation and experience with pion therapy

International Nuclear Information System (INIS)

Von Essen, C.F.; Blattmann, H.; Crawford, J.F.; Fessenden, P.; Pedroni, E.; Perret, C.; Salzmann, M.; Shortt, K.; Walder, E.

1982-01-01

The PIOTRON is a large solid angle superconducting channel built for the use of negative pi-mesons in radiotherapy. The pions are produced by protons of 590 MeV striking a target of molybdenum or beryllium. The pions are divided into 60 channels and deflected twice to enter the treatment volume radially. The momentum and the momentum band for all 60 channels can be chosen and the beam spot of Bragg peak pions at the isocenter of the applicator is a few centimeters in each direction. Dynamic scanning can thus achieve 3-dimensionally shaped treatment volumes. Two different methods are available: the ring scan, using changes of pion range; and the spot scan, involving translation of the patient through the fixed beam spot. Dose distributions of individual and multiple beams were plotted in a cylindrical water phantom. Radiobiological experiments with mammalian cells in gel and with mouse feet were performed. A special beam geometry using a sector of 15 beams was selected for the first treatments of patients with metastatic skin nodules. Six patients were treated. Acute skin reactions were scored and compared with those from orthovoltage therapy with comparable beam geometry. The RBE for 10 fractions is between 1.4 and 1.5. The next step involved treatment of patients inside water-bolus rings in preparation for dynamic therapy. Patients were then treated with the spot scan dynamic mode in the water bolus. The initial responses and reactions are favorable and confirm the feasibility and accuracy of dynamic pion therapy

Can we see scalar, pseudoscalar or tensor interactions in coherent pion production?

International Nuclear Information System (INIS)

Rein, D.

1988-01-01

The possibility to detect nonconventional scalar, pseudoscalar or tensor interactions (SPT) in the angular distribution of pions produced coherently in neutrino nucleus reactions is reexamined. It is found that the angular distribution does not differ qualitatively from a corresponding distribution arising from conventional vector-axial vector (VA) interactions unless the energy of the outgoing pion is restricted. Even then SPT interactions are likely to be overshadowed by transverse VA interactions which can mimic the former at finite although small momentum transfer Q 2 . (author)

Pions scatter by nuclei

International Nuclear Information System (INIS)

Huefner, J.

1975-01-01

Are pions a good tool to study nuclei. If the emphasis of this question rests on ''tool'', the answer must be ''not yet.'' The reason: one does not even understand how a pion interacts with a nucleus. This is part of the many-body problem for strongly interacting particles and its study is a basic problem in physics. One must investigate questions like: Can one understand pion-nucleus interactions from pion-nucleon physics. How does a Δ-resonance look in nuclei. Once one has solved those basic problems, there will be spinoffs in medical, technical and nuclear areas. Then pions can be used as a tool to study nuclear properties

Single pion and several pions production in π+p interactions at 1.6 GeV/c

International Nuclear Information System (INIS)

Jabiol, M.A.

1966-01-01

The production of ρ + , N 33 * , and η 0 was observed in π + p interactions at 1.6 GeV/c. In the reactions where one pion is created, the comparison between the experimental distribution of the ρ + and the N 33 * with the predictions of the peripheral model modified by absorption effects permits the conclusion that the contribution of this model is important, but that other effects such as interferences between ρ + and N 33 * are not negligible. In the reactions where several pions are created, the branching ratios of some decay modes of η0 are evaluated and the associated production of η 0 and N 33 * is observed. (author) [fr

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.)

Lattice results for low moments of light meson distribution amplitudes

International Nuclear Information System (INIS)

Arthur, R.; Boyle, P.A.; Juettner, A.

2010-12-01

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 π and K and the (longitudinally-polarised) vector mesons ρ, K * and φ. 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. (orig.)

Coherent and chaotic generation of pions from relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Nakamura, Hiroki; Seki, Ryoichi

2002-01-01

Based on the recent NA44 and WA98 two- and three-pion interferometry data together with the WA98 pion multiplicity information, we observe that the pions may be mostly emitted from chaotic sources in the peripheral events and coherent pions are mostly generated in the central events. A more refined analysis would be needed, however, to make our observation conclusive by quantifying various effects such as resonance formation of the emerging pions and also experimental uncertainties

N → Δ (1232) electromagnetic transition form factor and pion-nucleon dynamics at moderate energies

International Nuclear Information System (INIS)

Jurewicz, A.

1980-01-01

The dependence of the electromagnetic N → Δ (1232) transition form factor G/sup asterisk//sub M/(q 2 ) on q 2 , the four-momentum transfer squared, has been calculated with the use of relativistic dispersion relations supplemented with some dynamical assumptions. In the first place, they regard the phase of the magnetic dipole amplitude of electroproduction of pions on nucleons in the p 33 final state beyond the region of elastic unitarity. Namely, over the range from the lowest inelastic threshold up to 1780 MeV pion-nucleon c.m. energy, the phase in question has been identified with the real part of the respective phase shift of pion-nucleon scattering. Secondly, contributions to the dispersion integral from the higher energy region have been neglected. Finally, the polynomial ambiguity which appears in the problem has been fixed by requiring that the foregoing amplitude of electroproduction vanishes, independently of q 2 , at the upper end of the integration interval as defined above. These assumptions which preserve unitarity were shown previously to lead to very good results when applied to the calculation of the multipole amplitudes M/sup() 3/2/ 1 /sub +/ and E/sup() 3/2/ 1 /sub +/ of photopion production on nucleons in the Δ (1232) region. Now it is also shown that G/sup asterisk//sub M/(q 2 ) calculated in that fashion follows remarkably well the data over the whole range 0 2 2 currently covered by quantitative experimental studies. Some speculation concerning a possible dynamical rooting of the foregoing assumptions is presented

Pion inelastic scattering to the first three excited states of lithium-6

International Nuclear Information System (INIS)

Kiziah, R.R.

1984-10-01

Using the Energetic Pion Channel and Spectrometer system at the Clinton P. Anderson Meson Physics Facility, differential cross sections were measured for π + inelastic scattering to the 3 + , T=0, 2.185-MeV, 0 + , T=1, 3.563-MeV, and 2 + , T=0, 4.25-MeV states of 6 Li at incident pion energies of 120 and 180 MeV and laboratory scattering angles between 15 0 and 47 0 . Excitation functions were measured at a constant momentum transfer of approximately 109 MeV/c for incident pion energies from 100 to 260 MeV. The constant momentum transfer corresponds to the maxima of the angular distributions for π + inelastic scattering to the 3.563-MeV level. Microscopic calculations using the distorted-wave impulse approximation (DWIA) agree well with the measured angular distributions and excitation functions for the 2.185- and 4.25-MeV levels. However, microscopic DWIA calculations do not adequately reproduce the measured angular distributions for the 3.563-MeV level and fail to reproduce the observed anomalous excitation function. The shape of the 3.563-MeV excitation function is similar to that previously observed for π +- inelastic scattering to the 1 + , T=1, 15.11-MeV state of 12 C. The same mechanism may be responsible for the observed excitation functions of both ΔS=ΔT=1 transitions. A possible mechanism is the direct excitation of Δ particle-nucleon hole (Δ-h) components in the final state wave functions. Within the Δ-h model interpretation, the peak of the 3.563-MeV excitation function is reproduced with an estimated probability amplitude for the Δ-h component of the 3.563-MeV state with respect to the ground state of 0.01 less than or equal to β less than or equal to 0.13, a range of values of β consistent with the range estimated for the 15.11-MeV level of 12 C (0.026 less than or equal to β less than or equal to 0.096)

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.

Pion correlation from Skyrmion--anti-Skyrmion annihilation

International Nuclear Information System (INIS)

Lu, Y.; Amado, R.D.

1995-01-01

We study two pion correlations from Skyrmion and anti-Skyrmion collision, using the product ansatz and an approximate random grooming method for nucleon projection. The spatial-isospin coupling inherent in the Skyrme model, along with empirical averages, leads to correlations not only among pions of like charges but also among unlike charge types

Bose-Einstein correlations of three charged pions in hadronic $Z^{0}$ decays

CERN Document Server

Ackerstaff, K; Allison, J; Altekamp, N; Anderson, K J; Anderson, S; Arcelli, S; Asai, S; Ashby, S F; Axen, D A; Azuelos, Georges; Ball, A H; Barberio, E; Barlow, R J; Bartoldus, R; Batley, J Richard; Baumann, S; Bechtluft, J; Behnke, T; Bell, K W; Bella, G; Bentvelsen, Stanislaus Cornelius Maria; Bethke, Siegfried; Betts, S; Biebel, O; Biguzzi, A; Bird, S D; Blobel, Volker; Bloodworth, Ian J; Bobinski, M; Bock, P; Böhme, J; Boutemeur, M; Braibant, S; Bright-Thomas, P G; Brown, R M; Burckhart, Helfried J; Burgard, C; Bürgin, R; Capiluppi, P; Carnegie, R K; Carter, A A; Carter, J R; Chang, C Y; Charlton, D G; Chrisman, D; Ciocca, C; Clarke, P E L; Clay, E; Cohen, I; Conboy, J E; Cooke, O C; Couyoumtzelis, C; Coxe, R L; Cuffiani, M; Dado, S; Dallavalle, G M; Davis, R; De Jong, S; del Pozo, L A; de Roeck, A; Desch, Klaus; Dienes, B; Dixit, M S; Doucet, M; Dubbert, J; Duchovni, E; Duckeck, G; Duerdoth, I P; Eatough, D; Estabrooks, P G; Etzion, E; Evans, H G; Fabbri, Franco Luigi; Fanfani, A; Fanti, M; Faust, A A; Fiedler, F; Fierro, M; Fischer, H M; Fleck, I; Folman, R; Fürtjes, A; Futyan, D I; Gagnon, P; Gary, J W; Gascon, J; Gascon-Shotkin, S M; Geich-Gimbel, C; Geralis, T; Giacomelli, G; Giacomelli, P; Gibson, V; Gibson, W R; Gingrich, D M; Glenzinski, D A; Goldberg, J; Gorn, W; Grandi, C; Gross, E; Grunhaus, Jacob; Gruwé, M; Hanson, G G; Hansroul, M; Hapke, M; Hargrove, C K; Hartmann, C; Hauschild, M; Hawkes, C M; Hawkings, R; Hemingway, Richard J; Herndon, M; Herten, G; Heuer, R D; Hildreth, M D; Hill, J C; Hillier, S J; Hobson, P R; Höcker, Andreas; Homer, R James; Honma, A K; Horváth, D; Hossain, K R; Howard, R; Hüntemeyer, P; Igo-Kemenes, P; Imrie, D C; Ishii, K; Jacob, F R; Jawahery, A; Jeremie, H; Jimack, Martin Paul; Joly, A; Jones, C R; Jovanovic, P; Junk, T R; Karlen, D A; Kartvelishvili, V G; Kawagoe, K; Kawamoto, T; Kayal, P I; Keeler, Richard K; Kellogg, R G; Kennedy, B W; Klier, A; Kluth, S; Kobayashi, T; Kobel, M; Koetke, D S; Kokott, T P; Kolrep, M; Komamiya, S; Kowalewski, R V; Kress, T; Krieger, P; Von Krogh, J; Kyberd, P; Lafferty, G D; Lanske, D; Lauber, J; Lautenschlager, S R; Lawson, I; Layter, J G; Lazic, D; Lee, A M; Lefebvre, E; Lellouch, Daniel; Letts, J; Levinson, L; Liebisch, R; List, B; Littlewood, C; Lloyd, A W; Lloyd, S L; Loebinger, F K; Long, G D; Losty, Michael J; Ludwig, J; Liu, D; Macchiolo, A; MacPherson, A L; Mannelli, M; Marcellini, S; Markopoulos, C; Martin, A J; Martin, J P; Martínez, G; Mashimo, T; Mättig, P; McDonald, W J; McKenna, J A; McKigney, E A; McMahon, T J; McPherson, R A; Meijers, F; Menke, S; Merritt, F S; Mes, H; Meyer, J; Michelini, Aldo; Mihara, S; Mikenberg, G; Miller, D J; Mir, R; Mohr, W; Montanari, A; Mori, T; Nagai, K; Nakamura, I; Neal, H A; Nellen, B; Nisius, R; O'Neale, S W; Oakham, F G; Odorici, F; Ögren, H O; Oreglia, M J; Orito, S; Pálinkás, J; Pásztor, G; Pater, J R; Patrick, G N; Patt, J; Pérez-Ochoa, R; Petzold, S; Pfeifenschneider, P; Pilcher, J E; Pinfold, James L; Plane, D E; Poffenberger, P R; Poli, B; Polok, J; Przybycien, M B; Rembser, C; Rick, Hartmut; Robertson, S; Robins, S A; Rodning, N L; Roney, J M; Roscoe, K; Rossi, A M; Rozen, Y; Runge, K; Runólfsson, O; Rust, D R; Sachs, K; Saeki, T; Sahr, O; Sang, W M; Sarkisyan-Grinbaum, E; Sbarra, C; Schaile, A D; Schaile, O; Scharf, F; Scharff-Hansen, P; Schieck, J; Schmitt, B; Schmitt, S; Schöning, A; Schörner-Sadenius, T; Schröder, M; Schumacher, M; Schwick, C; Scott, W G; Seuster, R; Shears, T G; Shen, B C; Shepherd-Themistocleous, C H; Sherwood, P; Siroli, G P; Sittler, A; Skuja, A; Smith, A M; Snow, G A; Sobie, Randall J; Söldner-Rembold, S; Sproston, M; Stahl, A; Stephens, K; Steuerer, J; Stoll, K; Strom, D; Ströhmer, R; Tafirout, R; Talbot, S D; Tanaka, S; Taras, P; Tarem, S; Teuscher, R; Thiergen, M; Thomson, M A; Von Törne, E; Torrence, E; Towers, S; Trigger, I; Trócsányi, Z L; Tsur, E; Turcot, A S; Turner-Watson, M F; Van Kooten, R; Vannerem, P; Verzocchi, M; Vikas, P; Voss, H; Wäckerle, F; Wagner, A; Ward, C P; Ward, D R; Watkins, P M; Watson, A T; Watson, N K; Wells, P S; Wermes, N; White, J S; Wilson, G W; Wilson, J A; Wyatt, T R; Yamashita, S; Yekutieli, G; Zacek, V; Zer-Zion, D

1998-01-01

Bose-Einstein Correlations (BEC) of three identical charged pions were studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP. The genuine three-pion correlations, corrected for the Coulomb effect, were separated from the known two-pion correlations by a new subtraction procedure. A significant genuine three-pion BEC enhancement near threshold was observed having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029 (syst.) fm and a strength of \\lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041 (syst.). The Coulomb correction was found to increase the \\lambda_3 value by 0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the three-pion sample purity. A relation between the two-pion and the three-pion source parameters is discussed.

Beam energy and centrality dependence of two-pion Bose-Einstein correlations at SPS energies

Czech Academy of Sciences Publication Activity Database

Adamová, Dagmar; Agakichiev, G.; Appelshäuser, H.; Belaga, V.; Braun-Munzinger, P.; Campagnolo, R.; Castillo, A.; Cherlin, A.; Damjanović, S.; Dietel, T.; Dietrich, L.; Drees, A.; Esumi, S. I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glässel, P.; Hering, G.; Holeczek, J.; Kushpil, Vasilij; Lenkeit, B.; Ludolphs, W.; Maas, A.; Marín, A.; Milošević, J.; Milov, A.; Miśkowiec, D.; Musa, L.; Panebrattsev, Yu.; Petchenova, O.; Petráček, Vojtěch; Pfeiffer, A.; Rak, J.; Ravinovich, I.; Rehak, P.; Richter, M.; Sako, H.; Schmitz, W.; Schukraft, J.; Sedykh, S.; Seipp, W.; Sharma, A.; Shimansky, S.; Slívová, J.; Specht, H. J.; Stachel, J.; Šumbera, Michal; Tilsner, H.; Tserruya, I.; Wessels, J. P.; Wienold, T.; Windelband, B.; Wurm, J. P.; Xie, W.; Yurevich, S.; Yurevich, V. V.

2003-01-01

Roč. 714, 1/2 (2003), s. 124-144 ISSN 0375-9474 R&D Projects: GA ČR GA202/03/0879; GA AV ČR KSK1048102 Institutional research plan: CEZ:AV0Z1048901 Keywords : two-pion correlation function * heavy-ion collisions Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.761, year: 2003

Low energy scattering with a nontrivial pion

International Nuclear Information System (INIS)

Fariborz, Amir H.; Jora, Renata; Schechter, Joseph

2007-01-01

An earlier calculation in a generalized linear sigma model showed that the well-known current algebra formula for low energy pion-pion scattering held even though the massless Nambu Goldstone pion contained a small admixture of a two-quark two-antiquark field. Here we turn on the pion mass and note that the current algebra formula no longer holds exactly. We discuss this small deviation and also study the effects of a SU(3) symmetric quark mass type term on the masses and mixings of the eight SU(3) multiplets in the model. We calculate the s-wave scattering lengths, including the beyond current algebra theorem corrections due to the scalar mesons, and observe that the effect of the scalar mesons is to improve the agreement with experiment. In the process, we uncover the way in which linear sigma models give controlled corrections (due to the presence of scalar mesons) to the current algebra scattering formula. Such a feature is commonly thought to exist only in the nonlinear sigma model approach

Backward pion photoproduction

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.

Dosimetry of pion beams

International Nuclear Information System (INIS)

Dicello, J.F.

1975-01-01

Negative pion beams are probably the most esoteric and most complicated type of radiation which has been suggested for use in clinical radiotherapy. Because of the limited availability of pion beams in the past, even to nuclear physicists, there exist relatively fewer basic data for this modality. Pion dosimetry is discussed

Electromagnetic pion production in manifestly Lorentz invariant baryonic chiral perturbation theory; Elektromagnetische Pionproduktion in manifest Lorentz-invarianter baryonischer chiraler Stoerungstheorie

Energy Technology Data Exchange (ETDEWEB)

Lehnhart, B.C.

2007-05-15

This thesis is concerned with electromagnetic pion production within manifestly Lorentz-invariant chiral perturbation theory using the assumption of isospin symmetry. In a one-loop calculation up to the chiral order O(q{sup 4}), 105 Feynman diagrams contribute, consisting of 20 tree graphs and 85 loop diagrams. The tree graphs are classified as 16 pole diagrams and 4 contact graphs. Of the 85 loop diagrams, 50 diagrams are of order three and 35 diagrams are of fourth order. To calculate the pion production amplitude algorithms are developed on the basis of the Mathematica package FeynCalc. The one-photon-exchange approximation allows one to parametrise the pion production amplitude as the product of the polarisation vector of the (virtual) photon and the matrix element of the transition current. The polarisation vector is related to the leptonic vertex and the photon propagator and is well-known from QED. The dependence of the amplitude on the strong interaction is contained in the matrix element of the transition current, and we use chiral perturbation theory to describe this matrix element. The transition current can be expressed in terms of six gauge invariant amplitudes, each of which can again be decomposed into three isospin amplitudes. Linear combinations of these amplitudes allow us to describe the physical amplitudes. The one-loop integrals appearing within this calculation are determined numerically by the program LoopTools. In the case of tensorial integrals it is required to perform the method of Passarino and Veltman first. Furthermore, we apply the reformulated infrared regularisation which ensures that the results fulfill the chiral power counting. For this purpose algorithms are developed which determine the subtraction terms automatically. The obtained isospin amplitudes are integrated in the program MAID. As tests the s-wave multipoles E{sub 0+} and L{sub 0+} (using results up to chiral order O(q{sup 3})) are calculated in the threshold region

Probing nuclear correlations with pion-nucleus double charge exchange

International Nuclear Information System (INIS)

Ginocchio, J.N.

1988-01-01

In this paper we have calculated the lowest order pion double charge reaction mechanism using shell model wavefunctions of medium weight nuclei. We have the sequential reaction mechanism in which the pion undergoes two single-charge exchange scatterings on the valence neutrons. The distortion of the incoming, intermediate, and outgoing pion are included. The closure approximation is made for the intermediate states with an average excitation energy used in the pion propagator. The double-charge exchange is assumed to take place on the valence nucleons which are assumed to be in one spherical shell model orbital. 34 refs., 5 figs., 3 tabs

Pion parton distribution functions from lattice QCD

International Nuclear Information System (INIS)

Wetzorke, I.; Jansen, K.; Shindler, A.; Palombi, F.

2003-09-01

We report on recent results for the pion matrix element of the twist-2 operator corresponding to the average momentum of non-singlet quark densities. For the first time finite volume effects of this matrix element are investigated and come out to be surprisingly large. We use standard Wilson and non-perturbatively improved clover actions in order to control better the extrapolation to the continuum limit. Moreover, we compute, fully non-perturbatively, the renormalization group invariant matrix element, which allows a comparison with experimental results in a broad range of energy scales. Finally, we discuss the remaining uncertainties, the extrapolation to the chiral limit and the quenched approximation. (orig.)

p-wave pion production from nucleon-nucleon collisions

International Nuclear Information System (INIS)

Baru, V.; Epelbaum, E.; Haidenbauer, J.; Hanhart, C.; Kudryavtsev, A. E.; Lensky, V.; Meissner, U.-G.

2009-01-01

We investigate p-wave pion production in nucleon-nucleon collisions up to next-to-next-to-leading order in chiral effective field theory. In particular, we show that it is possible to describe simultaneously the p-wave amplitudes in the pn→ppπ - , pp→pnπ + , pp→dπ + channels by adjusting a single low-energy constant accompanying the short-range operator that is available at this order. This study provides a nontrivial test of the applicability of chiral effective field theory to reactions of the type NN→NNπ.

Two-Loop Gluon to Gluon-Gluon Splitting Amplitudes in QCD

International Nuclear Information System (INIS)

Bern, Z.

2004-01-01

Splitting amplitudes are universal functions governing the collinear behavior of scattering amplitudes for massless particles. We compute the two-loop g → gg splitting amplitudes in QCD, N = 1, and N = 4 super-Yang-Mills theories, which describe the limits of two-loop n-point amplitudes where two gluon momenta become parallel. They also represent an ingredient in a direct x-space computation of DGLAP evolution kernels at next-to-next-to-leading order. To obtain the splitting amplitudes, we use the unitarity sewing method. In contrast to the usual light-cone gauge treatment, our calculation does not rely on the principal-value or Mandelstam-Leibbrandt prescriptions, even though the loop integrals contain some of the denominators typically encountered in light-cone gauge. We reduce the integrals to a set of 13 master integrals using integration-by-parts and Lorentz invariance identities. The master integrals are computed with the aid of differential equations in the splitting momentum fraction z. The ε-poles of the splitting amplitudes are consistent with a formula due to Catani for the infrared singularities of two-loop scattering amplitudes. This consistency essentially provides an inductive proof of Catani's formula, as well as an ansatz for previously-unknown 1/ε pole terms having non-trivial color structure. Finite terms in the splitting amplitudes determine the collinear behavior of finite remainders in this formula

Total cross sections for pion charge exchange on the proton

International Nuclear Information System (INIS)

Breitschopf, J.

2006-01-01

This work describes the measurement of total SCX cross sections employing a new 4π scintillation counter to perform transmission measurements in the incident pion energy range from about 38 to 250 MeV. A small 4π 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 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 Δ-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 Δ 0 Breit-Wigner resonance describing the p 33 -waves. This shows that p-wave as well as s-wave effects should be considered in studies of isospin symmetry breaking. Interestingly

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

Pion polarizabilities measurement at COMPASS

CERN Document Server

Guskov, Alexey

2008-01-01

The electromagnetic structure of pions is probed in $\\pi^{−} + (A,Z)\\rightarrow\\pi^{−} + (A,Z) +\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\bar{\\alpha_{\\pi}})$ and the magnetic $(\\bar{\\beta_{\\pi}})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with $a \\pi^{−}$ beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction. The preliminary result for pion polarizabilities under the assumption of $\\bar{\\alpha_{\\pi}} + \\bar{\\beta_{\\pi}} =$ 0 is $\\ba...

Exclusive two-photon processes: Tests of QCD at the amplitude level

International Nuclear Information System (INIS)

Brodsky, S.J.

1992-07-01

Exclusive two-photon processes at large momentum transfer, particularly Compton scattering γp→γp and its crossed-channel reactions γγ→ bar pp and bar pp→γγ, can provide definitive information on the bound-state distributions of quarks in hadrons at the amplitude level. Recent theoretical work has shown that QCD predictions based on the factorization of long and short distance physics are already applicable at momentum transfers of order of a few GeV

Measurements of the spin rotation parameter R in high energy elastic scattering and helicity amplitudes at Serpukhov energies

International Nuclear Information System (INIS)

Pierrard, J.; Bruneton, C.; Bystricky, J.; Cozzika, G.; Deregel, J.; Ducros, Y.; Gaidot, A.; Khantine-Langlois, F.; Lehar, F.; Lesquen, A. de; Merlo, J.P.; Miyashita, S.; Movchet, J.; Raoul, J.C.; Van Rossum, L.; Kanavets, V.P.

1975-01-01

The spin rotation parameter R in pp and π + p elastic scattering at 45GeV/c has been measured at the Serpukhov accelerator, for /t/ ranging from 0.2 to 0.5(GeV/c) 2 . The results are presented, together with previous R measurements at 3.8, 6, 16 and 40GeV/c, and are compared with the predictions of Regge pole models. The equality of the values for R in proton-proton and pion-proton scattering, within the experimental errors, is a test of factorization of the residues. An s-channel helicity amplitude analysis for pion-nucleon scattering at 40GeV/c is made using all available data. Significant results are obtained for the non flip amplitude in isoscalar exchange and for flip amplitudes on both isovector and isoscalar exchanges. The helicity flip in isoscalar exchange is non negligible. The energy dependence of this amplitude, at 6, 16 and 40GeV/c, is compared with predictions of Regge pole models [fr

A new version of PIRK (elastic pion-nucleus scattering) to handle differing proton and neutron radii

International Nuclear Information System (INIS)

Funsten, H.O.

1979-01-01

This program is a modification of the Eisenstein-Miller program (1974) for calculating elastic pion-nucleus differential cross sections using free π-N scattering amplitudes. This revision permits the use of separate proton and neutron radii for the nuclear density function rho(r). (Auth.)

Pion nucleus scattering lengths

International Nuclear Information System (INIS)

Huang, W.T.; Levinson, C.A.; Banerjee, M.K.

1971-09-01

Soft pion theory and the Fubini-Furlan mass dispersion relations have been used to analyze the pion nucleon scattering lengths and obtain a value for the sigma commutator term. With this value and using the same principles, scattering lengths have been predicted for nuclei with mass number ranging from 6 to 23. Agreement with experiment is very good. For those who believe in the Gell-Mann-Levy sigma model, the evaluation of the commutator yields the value 0.26(m/sub σ//m/sub π/) 2 for the sigma nucleon coupling constant. The large dispersive corrections for the isosymmetric case implies that the basic idea behind many of the soft pion calculations, namely, slow variation of matrix elements from the soft pion limit to the physical pion mass, is not correct. 11 refs., 1 fig., 3 tabs

Pion polarizabilities measurement at COMPASS

CERN Document Server

Guskov, Alexey

2008-01-01

The electromagnetic structure of pions is probed in $\\pi^{−}+(A,Z) \\rightarrow\\pi^{−}+(A,Z)+\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric ($\\bar{\\alpha_{\\pi}}$) and the magnetic ($\\bar{\\beta_{\\pi}}$) polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with a $\\pi^{-}$ beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction.

Experimental study of the pion-xenon nucleus collisions at 3.5 GeV/c. Neutral pion production

International Nuclear Information System (INIS)

Strugalski, Z.; Abrosimov, A.T.; Wosinska, K.; Pawlak, T.; Nluta, J.; Sredniawa, B.; Il'ina, A.N.; Okhrimenko, L.S.; Peryt, W.; Miller, K.

1983-01-01

Experimental investigations of the neutral pion production are performed in pion-xenon collisions at 3.5 GeV/c. It is obtained that: 1) the average neutral pion multiplicity changes with the multiplicity of the protons emitted; 2) nearly 20% of the pions produced are emitted into the backward hemisphere; 3) the energy spectrum of the neutral pions is smooth; 4) the longitudinal component of the neutral pion momentum changes within the limits from -600 MeV/c to +1800 MeV/c; 5) the average value of the transversal component of the neutral pion momentum changes with the multiplicity of the protons emitted from approximately 270 to approximately 170 MeV/c; 6) the average value of the cosine of the neutral pion emission angle decreases with the multiplicity of the protons emitted

Complete disintegration of heavy nuclei induced by 340 GeV negative pions

International Nuclear Information System (INIS)

Ahmad, T.; Tariq, M.; Irfan, M.; Zafar, M.; Ahsan, M.Z.; Shafi, M.

1989-01-01

The total disintegration of AgBr nuclei caused by 340 GeV negative pions is investigated. The probability of this phenomena depends on the energy of the pion projectile. The angular distributions of grey and black tracks are investigated. Results for the rapidity gap correlation in these catastrophic destructions are also presented. (author). 17 refs., 5 tabs., 9 figs

Off-shell form factors in the soft photon limit for pion photoproduction

International Nuclear Information System (INIS)

Chumbalov, A.A.; Kamalov, S.S.

1991-01-01

The low energy theorems for the pion photoproduction are considered on the basis of the Adler-Dothan procedure. It is shown that the soft photon limit necessarily leads to the Born approximation for the π 0 -photoproduction amplitude at the threshold. All additional terms, according to the Adler-Dothan recipe, are to be neglected in the derivation of the LET. 5 refs.; 2 figs

Pion in a box

International Nuclear Information System (INIS)

Bietenholz, W.; Rakow, P.E.L.; Schierholz, G.; Regensburg Univ.

2010-02-01

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 δ regime. (orig.)

Multichannel 1 → 2 transition amplitudes in a finite volume

Energy Technology Data Exchange (ETDEWEB)

Briceno, Raul A. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Hansen, Maxwell T. [Univ. of Washington, Seattle, WA (United States); Walker-Loud, Andre [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)

2015-02-03

We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B⁰ → K*l⁺l⁻) or meson photo production (e.g., πγ* → ππ). We observe that, while the spectrum solely depends upon the on-shell scattering amplitude, the correlation functions also depend upon off-shell amplitudes. The main result of this work is a non-perturbative generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular-momentum. The result is exact up to exponentially suppressed corrections governed by the pion mass times the box size. We also apply our master equation to various examples, including two processes mentioned above as well as examples where the final state is an admixture of two open channels.

Study of the pion photoproduction amplitudes in the boundary of the physical region

International Nuclear Information System (INIS)

Mellado, I.

1980-01-01

The γsub(p) → π + n and γsub(n) → π - n amplitudes are determined in the resonance energy region for cos theta - +-1, by using modulus-phase dispersion relations and experimental differential cross section data. Numerical values for these amplitudes and for the corresponding isoscalar and isovector components are given. The isoscalar and isovector couplings of some resonances appearing in the amplitudes are also determined. (author)

A two-loop four-gluon helicity amplitude in QCD

Energy Technology Data Exchange (ETDEWEB)

Dixon, L.

2000-01-06

The authors present the two-loop pure gauge contribution to the gluon-gluon scattering amplitude with maximal helicity violation. The construction of the amplitude does not rely directly on Feynman diagrams, but instead uses its analytic properties 4--2{epsilon} dimensions. The authors evaluate the loop integrals appearing in the amplitude through order({epsilon}{sup 0})in terms of polylogarithms.

Pion elastic and inelastic scattering from 15N

International Nuclear Information System (INIS)

Saunders, D.P.

1991-12-01

Data were obtained on the Clinton P. Anderson Los Alamos Meson Physics Facility Energetic Pion Channel and Spectrometer for elastic and inelastic pion scattering from ground state 15 N nuclei. States observed here included those of 0.0, 5.27, 6.32, 7.16, 7.30, 7.57, 8.31, 8.57, 9.15, 9.76, 9.9, 10.7, 11.3, 11.9, 12.5, 12.9, 13.1, 14.1, 14.4, 14.6, 15.0, 16.5, 16.9, 17.2, 17.6, 18.3, 18.7, and 18.9 MeV excitation energies. Angular distributions were obtained for scattering at angles from 25 degree to 90 degree in 5 degree increments with an incident pion energy of 164 MeV. Optical model analyses of the elastic (0 MeV) angular distributions with equal point proton and neutron densities in both momentum and coordinate space formulations accurately predict the data, although the two formulations require different energy shifts to do so. This difference is thought to be a result of the more accurate nonlocal representation of the nuclear potential in the momentum space code. Additional spectra were obtained for scattering at constant momentum transfers of .94 and 1.57 fm -1 in order to generate constant momentum transfer excitation functions. Use of these excitation functions, σ(π + )/σ(π - ) ratios, and shell model DWIA calculations allowed identification of several excited states having shell-model-like, single particle-hole, pure spin-flip excitations. Shell model and collective model DWIA calculations, as well as the q = .94 and 1.57 fm -1 excitation functions and the σ(π + )/σ(π - ) ratios indicate that the other states are generally well represented by a shell model description with collective enhancements

An application of the Dipole Pomeron model to the pion-proton elastic scattering

International Nuclear Information System (INIS)

Covolan, R.J.M.; Leite, E.E.; Montanha, J.; Soares, M.S.

1994-01-01

The Pomeron model is applied to the pion-proton elastic scattering aiming to describe the total and differential cross sections and the ρ ratio between the scattering amplitude real and imaginary parts. It is also discussed how far the present available experimental results lead to the necessity of adopting a (α 0 > 1) supercritical trajectory. (author). 3 refs., 4 figs

Doorway-resonance model for pion-nucleon D- and F-wave scattering

International Nuclear Information System (INIS)

Ernst, D.J.; Parnell, G.E.; Assad, C.; Texas A and M Univ., College Station, TX

1990-01-01

A model for the resonant pion-nucleon D- and F-waves is developed which assumes that the pion-plus-nucleon couples to a resonance and that the resonance can serve as a doorway to the inelastic channels. With the use of simple form factors, the model is capable of reproducing the pion-nucleon phase shifts up to an energy of T π =1.4 GeV if the coupling of the elastic channel to the inelastic channels is taken from data as input into the model. A value for the mass of the resonance that would result in the absence of the coupling to decay channels is extracted from the data utilizing the model. This is the mass that is most easily modeled by bag models. For the non-resonant D- and F-wave channels a separable potential model is used. This model, like the resonance model, is developed utilizing the invariant amplitude which is free of kinematic singularities and uses invariant norms and phase spaces. The model is also applied to the S-wave channels. A relation between the resonance model and the Chew-Low model is discovered and used to derive an extended Chew-Low model which is applied to the P 13 , P 31 and P 33 channels. Implications of the model for understanding the range of the pion-nucleon interaction and the dynamic structure of the interaction are presented. (orig.)

Photoproduction of pions on low-energy protons

International Nuclear Information System (INIS)

Grushin, V.F.

1989-01-01

This paper reports that a study is made of the complete experiment problem and photoproduction of pions on protons. The problem of the volume and content of a complete experiment is solved in the area of photon energies up to 500 MeV for the channels γp-π + n and γp-π → π 0 p. Experimental data assuring a complete experiment are used for multipole analysis of the channels γp → π + n, π 0 p and the real and imaginary parts of s- and p-wave multipole amplitudes are obtained. Estimates are produced for the pole parameters (mass and width) of the Δ + 33 isobar. An electrical quadrupole amplitude of the transition γp → Δ + 33 was found which is significantly different form zero, indicating the existence of a tensor interaction between quarks in hadrons. Data on photoproduction on mesons are used to extract quantitative estimates of the vector and tensor constants of interaction of an ω meson with nucleons

N* resonances from KΛ amplitudes in sliced bins in energy

Energy Technology Data Exchange (ETDEWEB)

Anisovich, A.V.; Nikonov, V.A.; Sarantsev, A.V. [Helmholtz-Institute fuer Strahlen- und Kernphysik, Universitaet Bonn (Germany); Particle and Nuclear Physics Institute, Gatchina (Russian Federation); Burkert, V. [Thomas Jefferson Laboratory, Newport News, VA (United States); Hadzimehmedovic, M.; Omerovic, R.; Stahov, J. [University of Tuzla, Faculty of Natural Sciences and Mathematics, Tuzla (Bosnia and Herzegovina); Ireland, D.G. [University of Glasgow, SUPA, School of Physics and Astronomy, Glasgow (United Kingdom); Klempt, E. [Helmholtz-Institute fuer Strahlen- und Kernphysik, Universitaet Bonn (Germany); Thomas Jefferson Laboratory, Newport News, VA (United States); Svarc, A. [Rudjer Boskovic Institute, Zagreb (Croatia); Thoma, U. [Helmholtz-Institute fuer Strahlen- und Kernphysik, Universitaet Bonn (Germany)

2017-12-15

The two reactions γp → K{sup +}Λ and π{sup -}p → K{sup 0}Λ are analyzed to determine the leading photoproduction multipoles and the pion-induced partial wave amplitudes in slices of the invariant mass. The multipoles and the partial-wave amplitudes are simultaneously fitted in a multichannel Laurent+Pietarinen model (L+P model), which determines the poles in the complex energy plane on the second Riemann sheet close to the physical axes. The results from the L+P fit are compared with the results of an energy-dependent fit based on the Bonn-Gatchina (BnGa) approach. The study confirms the existence of several poles due to nucleon resonances in the region at about 1.9 GeV with quantum numbers J{sup P} = 1/2{sup +}, 3/2{sup +}, 1/2{sup -}, 3/2{sup -}, 5/2{sup -}. (orig.)

The effect of resonance production and diffraction on the inclusive spectra of pions and protons in 19 GeV/c pn interactions

International Nuclear Information System (INIS)

Bakken, V.; Breivik, F.O.; Jacobsen, T.

1984-01-01

Bubble chamber data on pn interactions at 19 GeV/c are used to investigate the effects of nucleon diffraction and resonance production on the inclusive x- and psub(T)sup(2)-distributions of protons and pions. The differential distributions of p, π - and distributions from the decay of the strong resonances Δsup(++)(1232) and Δ - (1232) and from rho 0 (770) are determined. The x-distributions of the protons in the two c.m. hemispheres become quite similar when the effect of diffraction and Δsup(++) is subtracted. The psub(T)sup(2)-distributions can then be described by a single exponential in the whole kinematic region. The net effect on the shape of the x-distributions of the pions due to diffraction, effect of these processes on the particle ratio π - /π + is investigated. By excluding the diffraction and Δsup(++)/Δ - production, the strength of the low-psub(T)sup(2) component of the psub(T)sup(2)-distributions of the pions is reduced, but it seems that diffraction and resonance production cannot account for all oft his low-psub(T)sup(2) enhancement

Universal pion freeze-out in heavy-ion collisions

CERN Document Server

Adamova, D; Appelshäuser, H; Belaga, V; Braun-Munzinger, P; Castillo, A; Cherlin, A; Damjanovic, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S I; Filimonov, K; Fomenko, K; Fraenkel, Zeev; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B C; Ludolphs, W; Maas, A; Marin, A; Milosevic, J; Milov, A; Miskowiec, D; Panebratsev, Yu A; Petchenova, O Yu; Petracek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Sako, H; Schükraft, Jürgen; Sedykh, S; Shimansky, S S; Slivova, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, Itzhak; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V; Schmitz, W

2003-01-01

Based on an evaluation of recent systematic data on two-pion interferometry and on measured particle yields at mid-rapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda_f reaches a value of approximately 2.5 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and its value is constant at all currently available beam energies from AGS to RHIC.

Chiral Dynamics in Pion-Photon Reactions Habilitation

CERN Document Server

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...

Pion condensation in symmetric nuclear matter

International Nuclear Information System (INIS)

Shamsunnahar, T.; Saha, S.; Kabir, K.; Nath, L.M.

1991-01-01

We have investigated the possibility of pion condensation in symmetric nuclear matter using a model of pion-nucleon interaction based essentially on chiral SU(2) x SU(2) symmetry. We have found that pion condensation is not possible for any finite value of the density. Consequently, no critical opalescence phenomenon is likely to be seen in pion-nucleus scattering nor is it likely to be possible to explain the EMC effect in terms of an increased number of pions in the nucleus. (author)

Pion production in relativistic collisions of nuclear drops

International Nuclear Information System (INIS)

Alonso, C.T.; Wilson, J.R.; McAbee, T.L.; Zingman, J.A.

1988-09-01

In a continuation of the long-standing effort of the nuclear physics community to model atomic nuclei as droplets of a specialized nuclear fluid, we have developed a hydrodynamic model for simulating the collisions of heavy nuclei at relativistic speeds. Our model couples ideal relativistic hydrodynamics with a new Monte Carlo treatment of dynamic pion production and tracking. The collective flow for low-energy (200 MeV/N) collisions predicted by this model compares favorably with results from earlier hydrodynamic calculations which used quite different numerical techniques. Our pion predictions at these lower energies appear to differ, however, from the experimental data on pion multiplicities. In this case of ultra-relativistic (200 GeV/N) collisions, our hydrodynamic model has produced baryonic matter distributions which are in reasonable agreement with recent experimental data. These results may shed some light on the sensitivity of relativistic collision data to the nuclear equation of state. 20 refs., 12 figs

In vitro and in vivo studies of the TRIUMF pion therapy beam

International Nuclear Information System (INIS)

Skarsgard, L.D.; Douglas, B.G.; Denekamp, J.; Chaplin, D.J.; Lam, G.K.; Harrison, R.W.; Kornelsen, R.O.; Palcic, B.

1985-01-01

Patient treatments at TRIUMF (Tri-University Meson Facility, Vancouver, B. C.) use a moving spot raster scan technique where the pion range is modulated in depth for each position of the moving spot. The spot scans in a stepwise fashion and can produce any desired field shape. This approach provides very good dose uniformity across the treatment field and allows maximum flexibility in shaping the treatment volume. Survival of cultured cells has been used as a biological dosimeter to test the isoeffectiveness of the pion dose distributions, which must be shaped in depth to compensate for the depth-dependent LET distribution. Isoeffectiveness across the treatment field has also been verified using this system, which involves irradiating cells supported in a gelatin matrix. The response of pig skin to pion irradiation at TRIUMF has provided a check on the in vivo RBE for acute effects derived from our earlier studies with mouse foot. In addition, the pig skin reactions have been followed for several months to assess the later dermal response. The RBE of our pion beam relative to 270 kVp X rays is approximately 1.5 for both the acute epidermal and the later dermal responses

Chiral symmetry and low energy pion-nucleon scattering

International Nuclear Information System (INIS)

Coon, S.A.

1999-01-01

In these lectures, I examine the effect of the meson factory πN data on the current algebra/PCAC program which describes chiral symmetry breaking in this system. After historical remarks on the current algebra/PCAC versus chiral Lagrangians approaches to chiral symmetry, and description of the need for πN amplitudes with virtual (off-mass-shell) pions in nuclear force models and other nuclear physics problems, I begin with kinematics and isospin aspects of the invariant amplitudes. A detailed introduction to the hadronic vector and axial-vector currents and the hypothesis of partially conserved axial-vector currents (PCAC) follows. I review and test against contemporary data the PCAC predictions of the Goldberger-Treiman relation, and the Adler consistency condition for a πN amplitude. Then comes a detailed description of the current algebra Ward-Takahashi identities in the chiral limit and a brief account of the on-shell current algebra Ward-Takahashi identities. The latter identities form the basis of so-called current algebra models of πN scattering. I then test these models against the contemporary empirical πN amplitudes extrapolated into the subthreshold region via dispersion relations. The scale and the t dependence of the 'sigma term' is determined by the recent data. (author)

Pion-induced knock-out reactions

International Nuclear Information System (INIS)

Jain, B.K.; Phatak, S.C.

1977-01-01

A strong absorption model for pion-induced Knock-out reactions is proposed. The distortion of the in-coming and out-going pions has been included by (1) computing pion wave number in nuclear medium (dispersive effect) and (2) excluding the central region of the nucleus where the real pion-absorption is dominant (absorption effect). In order to study the dependence of the (π + π + p) reaction on the off-shell pion-nucleon t-matrix, different off-shell extrapolations are used. The magnitude of the cross-sections seems to be sensitive to the type of off-shell extrapolation; their shapes, however, are similar. The theoretical results are compared with experimental data. The agreement between the theoretical results for separable off-shell extrapolation and the data is good. (author)

Measurement of pion double charge exchange on carbon-13, carbon-14, magnesium-26, and iron-56

International Nuclear Information System (INIS)

Seidl, P.A.

1985-02-01

Cross sections for the /sup 13,14/C, 26 Mg, 56 Fe(π + ,π - )/sup 13,14/O, 26 Si, 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 π/ 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 14 O(0 + , 5.92 MeV), 14 O(2 + , 7.77 MeV), 56 Ni(gs), 13 O(gs), and 13 O(4.21 MeV) are presented. The 13 O(4.21 MeV) state is postulated to have J/sup π/ = 1/2 - . 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 Δ 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 π/ > 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

Dosimetry and radiobiology of negative pions and heavy ions

International Nuclear Information System (INIS)

Raju, M.R.

1978-01-01

The depth dose distribution of pion beams has not been found superior to protons. Pion radiation quality at the plateau region is comparable to conventional low-LET radiations, and radiobiology results also indicate RBE values close to unity. In the pion stopping region, the radiation quality increases considerably. Radiobiology data for negative pions at the Bragg peak position clearly indicate the increase in RBE and the reduction in OER. Even at the Bragg peak position, compared to fast neutrons, the average LET of negative pions is lower. Pion radiobiology data have indicated lower RBE values and higher OER values compared to fast neutrons. The radiation quality of fast neutrons is in between that of carbon and neon ions at the peak region and that of neon ions at the plateau is lower than for fast neutrons. The mean LET value for helium ions, even at the distal end of the peak, is lower than for fast neutrons. Dose localization of heavy ions has been found to decrease slowly with increasing charge of the heavy ion. The intercellular contact that protects cells after exposure to low-LET radiations is not detected after exposure to heavy ions. Single and fractionated doses of heavy ions produce dose-response curves for heavy ions having reduced shoulders but similar slopes when compared to gamma rays. Fractionated treatments of heavy ions produce an enhanced effect in the peak region compared to the plateau region and could lead to a substantial gain in therapeutic ratio. The OER for protons was similar to that for x rays. The OER values for negative pions, helium ions, and carbon ions were larger, for neon ions similar, and for argon ions smaller when compared to fast neutrons.Negative pions, helium ions, and carbon ions may be very effective clinically because the radiation quality of these beams is similar to that of the mixed scheme of neutrons and x rays

Real and virtual pions in nuclei

International Nuclear Information System (INIS)

Giraud, N.

1984-02-01

The thesis first part is concerned with physical pion interaction with deuton, studied in a three-body problem frame. The elastic cross-section in the energy range near the resonance (3-3), has been deduced taking in account the pion virtual absorption. The second part is concerned with virtual pion in nuclei. In particular the virtual pion cloud around the nucleus has been studied and the effective constant coupling pion-nucleus has been deduced. This one is strongly reduced by polorazation effects of the nuclear medium (essentially by virtual excitation of the Δ isobar), in relation to its value for free nucleon collection. In the frame of the same polarization model, the pion field inside the nucleus has been studied also. This field is lowered for small momentum transfer. It is increased for large momentum transfer. This last phenomenon corresponds to critical opalescence related to phase transition of pion condensation [fr

Analyses of multi-pion Hanbury Brown–Twiss correlations for the pion-emitting sources with Bose–Einstein condensation

Science.gov (United States)

Bary, Ghulam; Ru, Peng; Zhang, Wei-Ning

2018-06-01

We calculate the three- and four-particle correlations of identical pions in an evolving pion gas (EPG) model with Bose–Einstein condensation. The multi-pion correlation functions in the EPG model are analyzed in different momentum intervals and compared with the experimental data for Pb–Pb collisions at \\sqrt{{s}{NN}}=2.76 {TeV}. It is found that the multi-pion correlation functions and cumulant correlation functions are sensitive to the condensation fraction of the EPG sources in the low average transverse-momentum intervals of the three and four pions. The model results of the multi-pion correlations are consistent with the experimental data in a considerable degree, which gives a source condensation fraction between 16% and 47%.

Pion parameters in nuclear medium from chiral perturbation theory and virial expansion

International Nuclear Information System (INIS)

Mallik, S.; Sarkar, Sourav

2004-01-01

We consider two methods to find the effective parameters of the pion traversing a nuclear medium. One is the first order chiral perturbation theoretic evaluation of the pion pole contribution to the two-point function of the axial-vector current. The other is the exact, first order virial expansion of the pion self-energy. We find that, although the results of chiral perturbation theory are not valid at normal nuclear density, those from the virial expansion may be reliable at such density. The latter predicts both the mass shift and the in-medium decay width of the pion to be small, of about a few MeV

Measurement of the pion form factor

International Nuclear Information System (INIS)

Dally, E.; Hauptman, J.; May, C.

1977-01-01

The pion form factor has been measured in the momentum transfer range of 0.03( 2 by scattering pions from atomic electrons in a liquid hydrogen target. The pion form factor is defined to be the elastic scattering cross section divided by that predicted for a point pion. The experiment has been performed in a 100 GeV/c negative pion beam incident on a 50 cm liquid hydrogen target at Fermi laboratory. The corrected form factor equals 0.33+-0.06 f 2 . Vector dominance predicts 0.40 f 2

The S-wave resonance contributions in the B{sup 0}{sub s} decays into ψ(2S,3S) plus pion pair

Energy Technology Data Exchange (ETDEWEB)

Rui, Zhou [North China University of Science and Technology, College of Sciences, Tangshan (China); Li, Ya [Nanjing Normal University, Department of Physics and Institute of Theoretical Physics, Nanjing, Jiangsu (China); Wang, Wen-Fei [Shanxi University, Institute of Theoretical Physics, Taiyuan, Shanxi (China)

2017-03-15

The three-body decays B{sup 0}{sub s} → ψ(2S,3S)π{sup +}π{sup -} are studied based on the perturbative QCD approach. With the help of the nonperturbative two-pion distribution amplitudes, the analysis is simplified into the quasi-two-body processes. Besides the traditional factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order vertex corrections are also included to cancel the scale dependence. The f{sub 0}(980), f{sub 0}(1500) resonance contributions as well as the nonresonant contributions are taken into account using the presently known ππ time-like scalar form factor for the s anti s component. It is found that the predicted B{sup 0}{sub s} → ψ(2S)π{sup +}π{sup -} decay spectra in the pion pair invariant mass shows a similar behavior as the experiment. The calculated S-wave contributions to the branching ratio of B{sup 0}{sub s} → ψ(2S)π{sup +}π{sup -} is 6.0 x 10{sup -5}, which is in agreement with the LHCb data B(B{sup 0}{sub s} → ψ(2S)π{sup +}π{sup -}) = (7.2±1.2) x 10{sup -5} within errors. The estimate of B(B{sup 0}{sub s} → ψ(3S)π{sup +}π{sup -}) can reach the order of 10{sup -5}, pending the corresponding measurements. (orig.)

Two- and three-pion quantum statistics correlations in Pb-Pb collisions at s N N = 2.76 TeV at the CERN Large Hadron Collider

NARCIS (Netherlands)

Abelev, B.; Adam, J.; Adamová, D.; Aggarwal, M. M.; Rinella, G. Aglieri; Agnello, M.; Agocs, A. G.; Agostinelli, A.; Agrawal, N.; Ahammed, Z.; Ahmad, N.; Masoodi, A. Ahmad; Ahmed, I.; Ahn, S. U.; Ahn, S. A.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altini, V.; Altinpinar, S.; Altsybeev, I.; Prado, C. Alves Garcia; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arbor, N.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Augustinus, A.; Averbeck, R.; Awes, T. C.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bairathi, V.; Bala, R.; Baldisseri, A.; Pedrosa, F. Baltasar Dos Santos; Bán, J.; Baral, R. C.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartke, J.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batyunya, B.; Batzing, P. C.; Baumann, C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bellwied, R.; Belmont-Moreno, E.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Berger, M. E.; Bergognon, A. A E; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Bjelogrlic, S.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Boehmer, F. V.; Bogdanov, A.; Bøggild, H.; Bogolyubsky, M.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Bornschein, J.; Bossú, F.; Botje, M.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Caffarri, D.; Cai, X.; Caines, H.; Caliva, A.; Villar, E. Calvo; Camerini, P.; Roman, V. Canoa; Carena, F.; Carena, W.; Carminati, F.; Díaz, A. Casanova; Castellanos, J. Castillo; Casula, E. A R; Catanescu, V.; Cavicchioli, C.; Sanchez, C. Ceballos; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Barroso, V. Chibante; Chinellato, D. D.; Chochula, P.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Balbastre, G. Conesa; Conesa Del Valle, Z.; Connors, M. E.; Contin, G.; Contreras, J. G.; Cormier, T. M.; Morales, Y. Corrales; Cortese, P.; Maldonado, I. Cortés; Cosentino, M. R.; Costa, F.; Crochet, P.; Albino, R. Cruz; Cuautle, E.; Cunqueiro, L.; Dainese, A.; Dang, R.; Danu, A.; Das, D.; Das, I.; Das, K.; Das, S.; Dash, A.; Dash, S.; De, S.; Delagrange, H.; Deloff, A.; Dénes, E.; D'Erasmo, G.; De Barros, G. O V; De Caro, A.; De Cataldo, G.; De Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; De Rooij, R.; Corchero, M. A Diaz; Dietel, T.; Divià, R.; Bari, D. Di; Liberto, S. Di; Mauro, A. Di; Nezza, P. Di; Djuvsland, O.; Dobrin, A.; Dobrowolski, T.; Gimenez, D. Domenicis; Dönigus, B.; Dordic, O.; Dorheim, S.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Majumdar, A. K Dutta; Elia, D.; Engel, H.; Erazmus, B.; Erdal, H. A.; Eschweiler, D.; Espagnon, B.; Estienne, M.; Esumi, S.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabris, D.; Faivre, J.; Falchieri, D.; Fantoni, A.; Fasel, M.; Fehlker, D.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Téllez, A. Fernández; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A S; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floratos, E.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Girard, M. Fusco; Gaardhøje, J. J.; Gagliardi, M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Garishvili, I.; Gerhard, J.; Germain, M.; Gheata, A.; Gheata, M.; Ghidini, B.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez, R.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Graczykowski, L. K.; Grajcarek, R.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Grosse-Oetringhaus, J. F.; Grossiord, J. Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Guilbaud, M.; Gulbrandsen, K.; Gulkanyan, H.; Gunji, T.; Gupta, A.; Gupta, R.; Khan, K. H.; Haake, R.; Haaland, I.M.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hanratty, L. D.; Hansen, A.; Harris, J. W.; Hartmann, H.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Hayrapetyan, A.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Corral, G. Herrera; Hess, B. A.; Hetland, K. F.; Hicks, B.; Hippolyte, B.; Hladky, J.; Hristov, P.; Huang, M.; Humanic, T. J.; Hutter, D.; Hwang, D. S.; Ianigro, J. C.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Incani, E.; Innocenti, G. M.; Ionita, C.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Ivanytskyi, O.; Jachołkowski, A.; Jahnke, C.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H S Y; Jena, S.; Bustamante, R. T Jimenez; Jones, P. G.; Jung, H.; Jusko, A.; Kalcher, S.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Uysal, A. Karasu; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kebschull, U.; Keidel, R.; Ketzer, B.; Khan, M. Mohisin; Khan, P.; Khan, S. 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C.; Lenhardt, M.; Lenti, V.; Leogrande, E.; Leoncino, M.; Monzón, I. León; Lévai, P.; Li, S.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Lohner, D.; Loizides, C.; Lopez, X.; Torres, E. López; Lu, X. G.; Luettig, P.; Lunardon, M.; Luo, J.; Luparello, G.; Luzzi, C.; Gago, A. M.; Jacobs, P. M.; Ma, R.; Maevskaya, A.; Mager, M.; Mahapatra, D. P.; Maire, A.; Malaev, M.; Cervantes, I. Maldonado; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Marín, A.; Markert, C.; Marquard, M.; Martashvili, I.; Martin, N. A.; Martinengo, P.; Martínez, M. I.; García, G. Martínez; Blanco, J. Martin; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazumder, R.; Mazzoni, M. A.; Meddi, F.; Menchaca-Rocha, A.; Pérez, J. Mercado; Meres, M.; Miake, Y.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitu, C. M.; Mlynarz, J.; Mohanty, B.; Molnar, L.; Zetina, L. Montaño; Montes, E.; Morando, M.; De Godoy, D. A Moreira; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Muhuri, S.; Mukherjee, M.; Müller, H.; Munhoz, M. G.; Murray, S.; Musa, L.; Musinsky, J.; Nandi, B. K.; Nania, R.; Nappi, E.; Nattrass, C.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nicassio, M.; Niculescu, M.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Nilsen, B. S.; Noferini, F.; Nomokonov, P.; Nooren, G.; Nyanin, A.; Nyatha, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Okatan, A.; Olah, L.; Oleniacz, J.; Da Silva, A. C Oliveira; Onderwaater, J.; Oppedisano, C.; Velasquez, A. Ortiz; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Pachmayer, Y.; Pachr, M.; Pagano, P.; Paić, G.; Painke, F.; Pajares, C.; Pal, S. K.; Palmeri, A.; Pant, D.; Papikyan, V.; Pappalardo, G. S.; Park, W. J.; Passfeld, A.; Patalakha, D. I.; Paticchio, V.; Paul, B.; Pawlak, T.; Peitzmann, T.; Da Costa, H. Pereira; Filho, E. Pereira De Oliveira; Peresunko, D.; Lara, C. E Pérez; Peryt, W.; Pesci, A.; Pestov, Y.; Petráček, V.; Petran, M.; Petris, M.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Planinic, M.; Płoskoń, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L M; Poghosyan, M. G.; Pohjoisaho, E. H O; Polichtchouk, B.; Poljak, N.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, V.; Potukuchi, B.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Rauf, A. W.; Razazi, V.; Read, K. F.; Real, J. S.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reicher, M.; Reidt, F.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J. P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Rivetti, A.; Rocco, E.; Cahuantzi, M. Rodríguez; Manso, A. Rodriguez; Røed, K.; Rogochaya, E.; Rohni, S.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossegger, S.; Rossi, A.; Roy, A.; Roy, C.; Roy, P.; Montero, A. J Rubio; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafaík, K.; Sahlmuller, B.; Sahoo, R.; Sahu, P. K.; Saini, J.; Salgado, C. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Castro, X. Sanchez; Rodríguez, F. J Sánchez; Šándor, L.; Sandoval, A.; Sano, M.; Santagati, G.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, P. A.; Scott, R.; Segato, G.; Seger, J. E.; Selyuzhenkov, I.; Seo, J.; Serradilla, E.; Sevcenco, A.; Shabetai, A.; Shabratova, G.; Shahoyan, R.; Shangaraev, A.; Sharma, N.; Sharma, S.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Skjerdal, K.; Smakal, R.; Smirnov, N.; Snellings, R. J M; Søgaard, C.; Soltz, R.; Song, J.; Song, M.; Soramel, F.; Sorensen, S.; Spacek, M.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stefanek, G.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Stolpovskiy, M.; Strmen, P.; Suaide, A. A P; Vasquez, M. A Subieta; Sugitate, T.; Suire, C.; Suleymanov, M.; Sultanov, R.; Šumbera, M.; Susa, T.; Symons, T. J M; De Toledo, A. Szanto; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Takahashi, J.; Tangaro, M. A.; Takaki, J. D Tapia; Peloni, A. Tarantola; Martinez, A. Tarazona; Tauro, A.; Muñoz, G. Tejeda; Telesca, A.; Terrevoli, C.; Minasyan, A. Ter; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Torii, H.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ulery, J.; Ullaland, K.; Ulrich, J.; Uras, A.; Usai, G. L.; Vajzer, M.; Vala, M.; Palomo, L. Valencia; Vallero, S.; Vyvre, P. Vande; Vannucci, L.; Van Hoorne, J. W.; Van Leeuwen, M.; Vargas, A.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vechernin, V.; Veldhoen, M.; Venaruzzo, M.; Vercellin, E.; Limón, S. Vergara; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Baillie, O. Villalobos; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; Von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wagner, V.; Wang, M.; Wang, Y.; Watanabe, D.; Weber, M.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C S; Windelband, B.; Winn, M.; Xiang, C.; Yaldo, C. G.; Yamaguchi, Y.; Yang, H.; Yang, P.; Yang, S.; Yano, S.; Yasnopolskiy, S.; Yi, J.; Yin, Z.; Yoo, I. K.; Yushmanov, I.; Zaccolo, V.; Zach, C.; Zaman, A.; Zampolli, C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, F.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhao, C.; Zhou, D.; Zhou, F.; Zhou, Y.; Zhu, H.; Zhu, J.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zoccarato, Y.; Zynovyev, M.; Zyzak, M.

2014-01-01

Correlations induced by quantum statistics are sensitive to the spatiotemporal extent as well as dynamics of particle-emitting sources in heavy-ion collisions. In addition, such correlations can be used to search for the presence of a coherent component of pion production. Two- and three-pion

Scruncher phase and amplitude control

International Nuclear Information System (INIS)

DeHaven, R.A.; Morris, C.L.; Johnson, R.; Davis, J.; O'Donnell, J.M.

1992-01-01

The analog controller for phase and amplitude control of a 402.5 MHz super conducting cavity is described in this paper. The cavity is a single cell with niobium explosively bonded to a copper cavity. It is used as an energy compressor for pions at the Clinton P. Anderson Meson Physics Facility (LAMPF). The controller maintains cavity frequency to within 4 degrees in phase of the LAMPF beam frequency. Field amplitude is maintained to within 2 percent. This control is accomplished at critical coupling (Q load of 1 x 10 9 ) with the use of only a 30 watt rf amplifier for accelerating fields of 6 MV/m. The design includes the use of piezoelectric crystals for fast resonance control. Three types of control, self excited, VCO, and a reference frequency driven, were tried on this cavity and we present a comparison of their performance. (Author) 4 figs., ref

SCRUNCHER phase and amplitude control

International Nuclear Information System (INIS)

DeHaven, R.A.; Morris, C.L.; Johnson, R.; Davis, J.; O'Donnell, J.M.

1992-01-01

The analog controller for phase and amplitude control of a 402.5 MHz super conducting cavity is described in this paper. The cavity is a single cell with niobium explosively bonded to a copper cavity. It is used as an energy compressor for pions at the Clinton P. Anderson Meson Physics Facility (LAMPF). The controller maintains cavity frequency to within 4 degrees in phase of the LAMPF beam frequency. Field amplitude is maintained to within 2 percent. This control is accomplished at critical coupling (Q loaded of 1 x 10 9 ) with the use of only a 30 watt rf amplifier for accelerating fields of 6 MV/m. The design includes the use of piezoelectric crystals for fast resonance control. Three types of control, self excited VCO, and a reference frequency driven, were tried on this cavity and we present a comparison of their performance

Spectator-velocity pions from heavy ions

International Nuclear Information System (INIS)

Rasmussen, J.; Ridout, J.; Murphy, D.; Radi, H.M.A.

1982-11-01

The discussion centers on pions in the velocity regions of target and projectile, where strong spectral features appear. The topics covered include stopped-pion studies, and convoy pions in the projectile frame

Two-nucleon electromagnetic current in chiral effective field theory: One-pion exchange and short-range contributions

International Nuclear Information System (INIS)

Koelling, S.; Epelbaum, E.; Krebs, H.; Meissner, U.-G.

2011-01-01

We derive the leading one-loop contribution to the one-pion exchange and short-range two-nucleon electromagnetic current operator in the framework of chiral effective field theory. The derivation is carried out using the method of unitary transformation. Explicit results for the current and charge densities are given in momentum and coordinate space.

The spin structure of the pion

Energy Technology Data Exchange (ETDEWEB)

Broemmel, D. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)]|[Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Diehl, M. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany); Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

2007-08-15

We present the first calculation of the transverse spin structure of the pion in lattice QCD. We find a characteristic asymmetry in the spatial distribution of transversely polarized quarks. This asymmetry is very similar in magnitude to the analogous asymmetry we previously obtained for quarks in the nucleon. Our results support the hypothesis that all Boer-Mulders functions are alike. (orig.)

Bayesian extraction of the parton distribution amplitude from the Bethe-Salpeter wave function

Science.gov (United States)

Gao, Fei; Chang, Lei; Liu, Yu-xin

2017-07-01

We propose a new numerical method to compute the 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 parton distribution amplitude (PDA) can be well determined. We confirm prior work on PDA computations, which was based on different methods.

Weak pion production off the nucleon

International Nuclear Information System (INIS)

Hernandez, E.; Nieves, J.; Valverde, M.

2007-01-01

We develop a model for the weak pion production off the nucleon, which besides the delta pole mechanism [weak excitation of the Δ(1232) resonance and its subsequent decay into Nπ], includes also some background terms required by chiral symmetry. We refit the C 5 A (q 2 ) form factor to the flux-averaged ν μ p→μ - pπ + ANL q 2 -differential cross section data, finding a substantially smaller contribution of the delta pole mechanism than traditionally assumed in the literature. Within this scheme, we calculate several differential and integrated cross sections, including pion angular distributions, induced by neutrinos and antineutrinos and driven both by charged and neutral currents. In all cases we find that the background terms produce quite significant effects, and that they lead to an overall improved description of the data, as compared to the case where only the delta pole mechanism is considered. We also show that the interference between the delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section, which are intimately linked to T-odd correlations in the contraction between the leptonic and hadronic tensors. However, these latter correlations do not imply a genuine violation of time-reversal invariance because of the existence of strong final state interaction effects

Polarization of protons produced in diffractive disintegration of deuterons by high-energy pions

International Nuclear Information System (INIS)

Gakh, G.Yi.; Rekalo, M.P.

1996-01-01

For the process of diffractive disintegration of unpolarized deuterons by the high-energy pions, π + d → π + p + n, the polarization characteristics of produced protons are calculated. Using the vector nature of the Pomeron exchange, the general structure of all components of proton polarization vector is found for d (π, π p) n. By the Pomeron-photon analogy, the amplitude of the process P + d → n + p is approximated by the isoscalar contribution of four Born diagrams similar to the case of deuteron electrodisintegration. Unitarization of the amplitude is achieved by introducing in multipole amplitudes the corresponding phases of np-scattering. The numerical calculation of all components of the polarization vector of protons, produced in the case of noncomplanar kinematics of the reaction π + d → π + p + n, is realized

On methods to determine the π0 multiplicity distribution and its moments from the observed γ radiation

International Nuclear Information System (INIS)

Ekspong, G.; Johansson, H.

1976-04-01

In high energy particle reactions where many neutral pions may be produced the information contained in the decay gamma radiation can be converted to information about the neutral pions. Two methods are described to obtain the moments of the multiplicity distribution of the neutral pions from the distribution of the number of electron-positron pairs. (Auth.)

Is the quasielastic pion cross section really bigger than the pion-nucleus reaction cross section

International Nuclear Information System (INIS)

Silbar, R.R.

1979-01-01

It is shown that soft pion charge exchanges may increase the inclusive (π + ,π 0 ') cross section, relative to the total quasielastic (π + ,π + ') cross section, by as much as a factor of two. 4 references

Pion condensation in symmetric nuclear matter

Science.gov (United States)

Kabir, K.; Saha, S.; Nath, L. M.

1988-01-01

Using a model which is based essentially on the chiral SU(2)×SU(2) symmetry of the pion-nucleon interaction, we examine the possibility of pion condensation in symmetric nucleon matter. We find that the pion condensation is not likely to occur in symmetric nuclear matter for any finite value of the nuclear density. Consequently, no critical opalescence phenomenom is expected to be seen in the pion-nucleus interaction.

Calculation of pion form factor

International Nuclear Information System (INIS)

Vahedi, N.; Amirarjomand, S.

1975-09-01

The pion form factor is calculated using the structure function Wsub(2), which incorporates kinematical constraints, threshold behaviour and scaling. The Bloom-Gilman sum rule is used and only the two leading Regge trajectories are taken into account

Production and decay of baryonic resonances in pion induced reactions

Directory of Open Access Journals (Sweden)

Przygoda Witold

2016-01-01

Full Text Available Pion induced reactions give unique opportunities for an unambiguous description of baryonic resonances and their coupling channels. A systematic energy scan and high precision data, in conjunction with a partial wave analysis, allow for the study of the excitation function of the various contributions. A review of available world data unravels strong need for modern facilities delivering measurements with a pion beam. Recently, HADES collaboration collected data in pion-induced reactions on light (12C and heavy (74W nuclei at a beam momentum of 1.7 GeV/c dedicated to strangeness production. It was followed by a systematic scan at four different pion beam momenta (0.656, 0.69, 0.748 and 0.8 GeV/c in π− − p reaction in order to tackle the role of N(1520 resonance in conjunction with the intermediate ρ production. First results on exclusive channels with one pion (π− p and two pions (nπ+π−, pπ−π0 in the final state are discussed.

Monte-Carlo simulation of hadronic shower Part 2: The PION calorimeter

Energy Technology Data Exchange (ETDEWEB)

Amatuni, Ts A; Mamidjanyan, E A; Sanossyan, Kh N

1993-12-31

Hadronic showers for four energy intervals from 0,5 to 5 TeV have been simulated using the MARS 10 code and the experimental energy and angle distributions of cosmic ray hadrons incident on the PION iron-ionization calorimeter. The longitudinal energy depositions are compared with the experimental results and satisfactory agreement is observed. The average characteristics of hadronic showers initiated by 0,3, 0,5, 1, 2,5, 10 and 20 TeV incident protons, neutrons and pions are studied and parametrizations for the longitudinal and transverse shower profiles are obtained. A new formula for the lateral profile is proposed. The leakage and albedo from the PION calorimeter and the energy spectra of the leakage and albedo particles are also estimated. 29 refs.

Two-pion Bose-Einstein correlations in $pp$ collisions at $\\sqrt{s}$=900 GeV

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Aamodt, K; Abeysekara, U; Abrahantes Quintana, A; Abramyan, A; Adamová, D; Aggarwal, M M; Aglieri Rinella, G; Agocs, A G; Aguilar Salazar, S; Ahammed, Z; Ahmad, A; Ahmad, N; Ahn, S U; Akimoto, R; Akindinov, A; Aleksandrov, D; Alessandro, B; Antolfaro Molina, R; Alici, A; Almaráz Aviña, E; Alme, J; Alt, T; Altini, V; Altinpinar, S; Andrei, C; Andronic, A; Anelli, G; Angelov, V; Anson, C; Anticic, T; Antinori, F; Antinori, S; Antipin, K; Antonczyk, D; Antonioli, P; Anzo, A; Aphecetche, L; Appelshäuser, H; Arcelli, S; Arceo, R; Arend, A; Armesto, N; Arnaldi, R; Aronsson, T; Arsene, I C; Asryan, A; Augustinus, A; Averbeck, R; Awes, T C; Äystö, J; Azmi, M D; Bablok, S; Bach, M; Badalà, A; Baek, Y W; Bagnasco, S; Bailhache, R; Bala, R; Baldisseri, A; Baldit, A; Bán, J; Barbera, R; Barnaföldi, G G; Barnby, L S; Barret, V; Bartke, J; Barile, F; Basile, M; Basmanov, V; Bastid, N; Bathen, B; Batigne, G; Batyunya, B; Baumann, C; Bearden, I G; Becker, B; Belikov, I; Bellwied, R; Belmont-Moreno, E; Belogianni, A; Benhabib, L; Beole, S; Berceanu, I; Bercuci, A; Berdermann, E; Berdnikov, Y; Betev, L; Bhasin, A; Bhati, A K; Bianchi, L; Bianchi, N; Bianchin, C; Bielcík, J; Bielcíková, J; Bilandzic, A; Bimbot, L; Biolcati, E; Blanc, A; Blanco, F; Blanco, F; Blau, D; Blume, C; Boccioli, M; Bock, N; Bogdanov, A; Bøggild, H; Bogolyubsky, M; Bohm, J; Boldizsár, L; Bombara, M; Bombonati, C; Bondila, M; Borel, H; Borisov, A; Bortolin, C; Bose, S; Bosisio, L; Bossú, F; Botje, M; Böttger, S; Bourdaud, G; Boyer, B; Braun, M; Braun-Munzinger, P; Bravina, L; Bregant, M; Breitner, T; Bruckner, G; Brun, R; Bruna, E; Bruno, G E; Budnikov, D; Buesching, H; Buncic, P; Busch, O; Buthelezi, Z; Caffarri, D; Cai, X; Caines, H; Calvo, E; Camacho, E; Camerini, P; Campbell, M; Canoa Roman, V; Capitani, G P; Cara Romeo, G; Carena, F; Carena, W; Carminati, F; Casanova Díaz, A; Caselle, M; Castillo Castellanos, J; Castillo Hernandez, J F; Catanescu, V; Cattaruzza, E; Cavicchioli, C; Cerello, P; Chambert, V; Chang, B; Chapeland, S; Charpy, A; Charvet, J L; Chattopadhyay, S; Chattopadhyay, S; Cherney, M; Cheshkov, C; Cheynis, B; Chiavassa, E; Chibante Barroso, V; Chinellato, D D; Chochula, P; Choi, K; Chojnacki, M; Christakoglou, P; Christensen, C H; Christiansen, P; Chujo, T; Chuman, F; Cicalo, C; Cifarelli, L; Cindolo, F; Cleymans, J; Cobanoglu, O; Coffin, J P; Coli, S; Colla, A; Conesa Balbastre, G; Conesa del Valle, Z; Conner, E S; Constantin, P; Contin, G; Contreras, J G; Corrales Morales, Y; Cormier, T M; Cortese, P; Cortés Maldonado, I; Cosentino, M R; Costa, F; Cotallo, M E; Crescio, E; Crochet, P; Cuautle, E; Cunqueiro, L; Cussonneau, J; Dainese, A; Dalsgaard, H H; Danu, A; Das, I; Dash, A; Dash, S; de Barros, G O V; De Caro, A; de Cataldo, G; de Cuveland, J; De Falco, A; De Gaspari, M; de Groot, J; De Gruttola, D; De Marco, N; De Pasquale, S; De Remigis, R; de Rooij, R; de Vaux, G; Delagrange, H; Delgado, Y; Dellacasa, G; Deloff, A; Demanov, V; Dénes, E; Deppman, A; D'Erasmo, G; Derkach, D; Devaux, A; Di Bari, D; Di Giglio, C; Di Liberto, S; Di Mauro, A; Di Nezza, P; Dialinas, M; Díaz, L; Díaz, R; Dietel, T; Divià, R; Djuvsland, Ø; Dobretsov, V; Dobrin, A; Dobrowolski, T; Dönigus, B; Domínguez, I; Dordic, O; Dubey, A K; Dubuisson, J; Ducroux, L; Dupieux, P; Dutta Majumdar, A K; Dutta Majumdar, M R; Elia, D; Emschermann, D; Enokizono, A; Espagnon, B; Estienne, M; Esumi, S; Evans, D; Evrard, S; Eyyubova, G; Fabjan, C W; Fabris, D; Faivre, J; Falchieri, D; Fantoni, A; Fasel, M; Fateev, O; Fearick, R; Fedunov, A; Fehlker, D; Fekete, V; Felea, D; Fenton-Olsen, B; Feofilov, G; Fernández Téllez, A; Ferreiro, E G; Ferretti, A; Ferretti, R; Figueredo, M A S; Filchagin, S; Fini, R; Fionda, F M; Fiore, E M; Floris, M; Fodor, Z; Foertsch, S; Foka, P; Fokin, S; Formenti, F; Fragiacomo, E; Fragkiadakis, M; Frankenfeld, U; Frolov, A; Fuchs, U; Furano, F; Furget, C; Fusco Girard, M; Gaardhøje, J J; Gadrat, S; Gagliardi, M; Gago, A; Gallio, M; Ganoti, P; Ganti, M S; Garabatos, C; García Trapaga, C; Gebelein, J; Gemme, R; Germain, M; Gheata, A; Gheata, M; Ghidini, B; Ghosh, P; Giraudo, G; Giubellino, P; Gladysz-Dziadus, E; Glasow, R; Glässel, P; Glenn, A; Gomez Jiménez, R; González Santos, H; González-Trueba, L H; González-Zamora, P; Gorbunov, S; Gorbunov, Y; Gotovac, S; Gottschlag, H; Grabski, V; Grajcarek, R; Grelli, A; Grigoras, A; Grigoras, C; Grigoriev, V; Grigoryan, A; Grigoryan, S; Grinyov, B; Grion, N; Gros, P; Grosse-Oetringhaus, J F; Grossiord, J Y; Grosso, R; Guber, F; Guernane, R; Guerra, C; Guerzoni, B; Gulbrandsen, K; Gulkanyan, H; Gunji, T; Gupta, A; Gupta, R; Gustafsson, H A; Gutbrod, H; Haaland, Ø; Hadjidakis, C; Haiduc, M; Hamagaki, H; Hamar, G; Hamblen, J; Han, B H; Harris, J W; Hartig, M; Harutyunyan, A; Hasch, D; Hasegan, D; Hatzifotiadou, D; Hayrapetyan, A; Heide, M; Heinz, M; Helstrup, H; Herghelegiu, A; Hernández, C; Herrera Corral, G; Herrmann, N; Hetland, K F; Hicks, B; Hiei, A; Hille, P T; Hippolyte, B; Horaguchi, T; Hori, Y; Hristov, P; Hrivnácová, I; Hu, S; Huang, M; Huber, S; Humanic, T J; Hutter, D; Hwang, D S; Ichou, R; Ilkaev, R; Ilkiv, I; Inaba, M; Innocenti, P G; Ippolitov, M; Irfan, M; Ivan, C; Ivanov, A; Ivanov, M; Ivanov, V; Iwasaki, T; Jachokowski, A; Jacobs, P; Jancurová, L; Jangal, S; Janik, R; Jena, C; Jena, S; Jirden, L; Jones, G T; Jones, P G; Jovanovic, P; Jung, H; Jung, W; Jusko, A; Kaidalov, A B; Kalcher, S; Kalinák, P; Kalisky, M; Kalliokoski, T; Kalweit, A; Kamal, A; Kamermans, R; Kanaki, K; Kang, E; Kang, J H; Kapitan, J; Kaplin, V; Kapusta, S; Karavichev, O; Karavicheva, T; Karpechev, E; Kazantsev, A; Kebschull, U; Keidel, R; Khan, M M; Khan, S A; Khanzadeev, A; Kharlov, Y; Kikola, D; Kileng, B; Kileng, B; Kim, D J; Kim, D S; Kim, D W; Kim, H N; Kim, J; Kim, J H; Kim, J S; Kim, M; Kim, M; Kim, S H; Kim, S; Kim, Y; Kirsch, S; Kisel, I; Kiselev, S; Kisiel, A; Klay, J L; Klein, J; Klein-Bösing, C; Kliemant, M; Klovning, A; Kluge, A; Knichel, M L; Kniege, S; Koch, K; Kolevatov, R; Kolojvari, A; Kondratiev, V; Kondratyeva, N; Konevskih, A; Kornas, E; Kour, R; Kowalski, M; Kox, S; Kozlov, K; Kral, J; Králik, I; Kramer, F; Kraus, I; Kravcáková, A; Krawutschke, T; Krivda, M; Krumbhorn, D; Krus, M; Kryshen, E; Krzewicki, M; Kucheriaev, Y; Kuhn, C; Kuijer, P G; Kumar, L; Kumar, N; Kupczak, R; Kurashvili, P; Kurepin, A; Kurepin, A N; Kuryakin, A; Kushpil, S; Kushpil, V; Kutouski, M; Kvaerno, H; Kweon, M J; Kwon, Y; La Rocca, P; Lackner, F; Ladron de Guevara, P; Lafage, V; Lal, C; Lara, C; Larsen, D T; Laurenti, G; Lazzeroni, C; Le Bornec, Y; Le Bris, N; Lee, H; Lee, K S; Lee, S C; Lefèvre, F; Lenhardt, M; Leistam, L; Lehnert, J; Lenti, V; Leon, H; Leon Monzon, I; Leon Vargas, H; Lévai, P; Li, X; Li, Y; Lietava, R; Lindal, S; Lindenstruth, V; Lippmann, C; Lisa, M A; Liu, L; Loginov, V; Lohn, S; Lopez, X; Lopez Noriega, M; Lopez-Ramírez, R; Lopez Torres, E; Løvhøiden, G; Lozea Feijo Soares, A; Lu, S; Lunardon, M; Luparello, G; Luquin, L; Lutz, J R; Ma, K; Ma, R; Madagodahettige-Don, D M; Maevskaya, A; Mager, M; Mahapatra, D P; Maire, A; Makhlyueva, I; Mal'Kevich, D; Malaev, M; Malagalage, K J; Maldonado Cervantes, I; Malek, M; Malkiewicz, T; Malzacher, P; Mamonov, A; Manceau, L; Mangotra, L; Manko, V; Manso, F; Manzari, V; Mao, Y; Mares, J; Margagliotti, G V; Margotti, A; Marín, A; Martashvili, I; Martinengo, P; Martínez Hernández, M I; Martínez Davalos, A; Martínez García, G; Maruyama, Y; Marzari Chiesa, A; Masciocchi, S; Masera, M; Masetti, M; Masoni, A; Massacrier, L; Mastromarco, M; Mastroserio, A; Matthews, Z L; Matyja, A; Mayani, D; Mazza, G; Mazzoni, M A; Meddi, F; Menchaca-Rocha, A; Mendez Lorenzo, P; Meoni, M; Mercado Pérez, J; Mereu, P; Miake, Y; Michalon, A; Miftakhov, N; Milano, L; Milosevic, J; Minafra, F; Mischke, A; Miskowiec, D; Mitu, C; Mizoguchi, K; Mlynarz, J; Mohanty, B; Molnar, L; Mondal, M M; Montaño Zetina, L; Monteno, M; Montes, E; Morando, M; Moretto, S; Morsch, A; Moukhanova, T; Muccifora, V; Mudnic, E; Muhuri, S; Müller, H; Munhoz, M G; Munoz, J; Musa, L; Musso, A; Nandi, B K; Nania, R; 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Turvey, A; Tveter, T S; Tydesjö, H; Tywoniuk, K; Ulery, J; Ullaland, K; Uras, A; Urbán, J; Urciuoli, G M; Usai, G L; Vacchi, A; Vala, M; Valencia Palomo, L; Vallero, S; van der Kolk, N; Vande Vyvre, P; van Leeuwen, M; Vannucci, L; Vargas, A; Varma, R; Vasiliev, A; Vassiliev, I; Vasileiou, M; Vechernin, V; Venaruzzo, M; Vercellin, E; Vergara, S; Vernet, R; Verweij, M; Vetlitskiy, I; Vickovic, L; Viesti, G; Vikhlyantsev, O; Vilakazi, Z; Villalobos Baillie, O; Vinogradov, A; Vinogradov, L; Vinogradov, Y; Virgili, T; Viyogi, Y P; Vodopianov, A; Voloshin, K; Voloshin, S; Volpe, G; von Haller, B; Vranic, D; Vrláková, J; Vulpescu, B; Wagner, B; Wagner, V; Wallet, L; Wan, R; Wang, D; Wang, Y; Wang, Y; Watanabe, K; Wen, Q; Wessels, J; Westerhoff, U; Wiechula, J; Wikne, J; Wilk, A; Wilk, G; Williams, M C S; Willis, N; Windelband, B; Xu, C; Yang, C; Yang, H; Yasnopolskiy, S; Yermia, F; Yi, J; Yin, Z; Yokoyama, H; Yoo, I K; Yuan, X; Yurevich, V; Yushmanov, I; Zabrodin, E; Zagreev, B; Zalite, A; Zampolli, C; Zanevsky, Yu; Zaporozhets, S; Zarochentsev, A; Závada, P; Zbroszczyk, H; Zelnicek, P; Zenin, A; Zepeda, A; Zgura, I; Zhalov, M; Zhang, X; Zhou, D; Zhou, S; Zhu, J; Zichichi, A; Zinchenko, A; Zinovjev, G; Zoccarato, Y; Zychácek, V; Zynovyev, M

2010-01-01

We report on the measurement of two-pion correlation functions from pp collisions at sqrt(s)=900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the HBT radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at RHIC and at Tevatron, is not manifest in our data.

Pion production in nucleus--nucleus collisions

International Nuclear Information System (INIS)

Schroeder, L.S.

1975-06-01

Current work on pion production in high-energy nucleus-nucleus collisions is reviewed. The majority of existing data are of the inclusive variety in which a single final state pion is detected. Experimental data are compared and their possible contributions to obtaining new information on nuclear structure is discussed. Various models which attempt to explain the observed single-inclusive-pion spectra either on the basis of a nucleon-nucleus interaction in which Fermi motion is included or on some type of cooperative model are examined. Other areas of interest involving pion production include tests of charge symmetry and pion multiplicities. (9 figures, 1 table) (U.S.)

N ≥ 4 Supergravity Amplitudes from Gauge Theory at Two Loops

International Nuclear Information System (INIS)

Boucher-Veronneau, Camille

2012-01-01

We present the full two-loop four-graviton amplitudes in N = 4, 5, 6 supergravity. These results were obtained using the double-copy structure of gravity, which follows from the recently conjectured color-kinematics duality in gauge theory. The two-loop four-gluon scattering amplitudes in N = 0, 1, 2 supersymmetric gauge theory are a second essential ingredient. The gravity amplitudes have the expected infrared behavior: the two-loop divergences are given in terms of the squares of the corresponding one-loop amplitudes. The finite remainders are presented in a compact form. The finite remainder for N = 8 supergravity is also presented, in a form that utilizes a pure function with a very simple symbol.

Pion condensation in symmetric nuclear matter

International Nuclear Information System (INIS)

Kabir, K.; Saha, S.; Nath, L.M.

1987-09-01

Using a model which is based essentially on the chiral SU(2)xSU(2) symmetry of the pion-nucleon interaction, we examine the possibility of pion condensation in symmetric nucleon matter. We find that the pion condensation is not likely to occur in symmetric nuclear matter for any finite value of the nuclear density. Consequently, no critical opalescence phenomenon is expected to be seen in the pion-nucleus interaction. (author). 20 refs

Bayesian extraction of the parton distribution amplitude from the Bethe–Salpeter wave function

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Fei Gao

2017-07-01

Full Text Available We propose a new numerical method to compute the 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 parton distribution amplitude (PDA can be well determined. We confirm prior work on PDA computations, which was based on different methods.

Quark bag coupling to finite size pions

International Nuclear Information System (INIS)

De Kam, J.; Pirner, H.J.

1982-01-01

A standard approximation in theories of quark bags coupled to a pion field is to treat the pion as an elementary field ignoring its substructure and finite size. A difficulty associated with these treatments in the lack of stability of the quark bag due to the rapid increase of the pion pressure on the bad as the bag size diminishes. We investigate the effects of the finite size of the qanti q pion on the pion quark bag coupling by means of a simple nonlocal pion quark interaction. With this amendment the pion pressure on the bag vanishes if the bag size goes to zero. No stability problems are encountered in this description. Furthermore, for extended pions, no longer a maximum is set to the bag parameter B. Therefore 'little bag' solutions may be found provided that B is large enough. We also discuss the possibility of a second minimum in the bag energy function. (orig.)

On the joint distribution of excursion duration and amplitude of a narrow-band Gaussian process

DEFF Research Database (Denmark)

Ghane, Mahdi; Gao, Zhen; Blanke, Mogens

2018-01-01

of amplitude and period are limited to excursion through a mean-level or to describe the asymptotic behavior of high level excursions. This paper extends the knowledge by presenting a theoretical derivation of probability of wave exceedance amplitude and duration, for a narrow-band Gaussian process......The probability density of crest amplitude and of duration of exceeding a given level are used in many theoretical and practical problems in engineering. The joint density is essential for design of constructions that are subjected to waves and wind. The presently available joint distributions...... distribution, as expected, and that the marginal distribution of excursion duration works both for asymptotic and non-asymptotic cases. The suggested model is found to be a good replacement for the empirical distributions that are widely used. Results from simulations of narrow-band Gaussian processes, real...

Estimates of the pion-nucleon sigma term using dispersion relations and taking into account the relation between chiral and scale invariance breaking

International Nuclear Information System (INIS)

Efrosinin, V.P.; Zaikin, D.A.

1983-01-01

We study the possible reasons for the disagreement between the estimates of the pion-nucleon sigma term obtained by the method of dispersion relations with extrapolation to the Cheng-Dashen point and by other methods which do not involve this extrapolation. One reason for the disagreement may be the nonanalyticity of the πN amplitude in the variable t for ν = 0. We propose a method for estimating the sigma term using the threshold data for the πN amplitude, in which the effect of this nonanalyticity is minimized. We discuss the relation between scale invariance violation and chiral symmetry breaking and give the corresponding estimate of the sigma term. The two estimates are similar (42 and 34 MeV) and are in agreement when the uncertainties of the two methods are taken into consideration

P-odd two-pion potentials and asymmetry of pp scattering at low energies

International Nuclear Information System (INIS)

Musakhanov, M.M.; Podgornov, Y.Y.

1986-01-01

The asymmetry of pp scattering A/sub p//sub p/ is calculated using the potential approach for incident proton energies of 15 and 45 MeV taking into account the isovector P-odd two-pion interaction. The corresponding 2π potentials are obtained in the static approximation of the noncovariant technique taking into account Δ-isobar configurations. The pion-baryon cutoff form factors are taken from chiral bag models. Owing to the lack of reliable information on the nucleon bag radius R, the contribution of 2π exchange to A/sub p//sub p/ is given for the fairly wide range R = 0.4--1.0 F. The strong interaction is taken into account by the introduction of the phenomenological Reid soft-core and Paris potentials. It is shown that most of the 2π-exchange contribution comes from the region where the internucleon separations are larger than they are where the contribution of rho 0 - and ω-meson exchange dominates and that the former contribution must be included in A/sub p//sub p/. The resulting contribution of the 2π potential to A/sub p//sub p/ is of the same order as the contribution of the rho 0 and ω potentials

Stopped pion absorption by medium and heavy nuclei in the cascade-exciton model

International Nuclear Information System (INIS)

Mashnik, S.G.

1992-03-01

A large variety of experimental data on stopped negative pion absorption by nuclei from C to Bi (energy spectra and multiplicities of n, p, d, t, 3 He and 4 He; angular correlations of two secondary particles; spectra of the energy release in the ''live'' 28 Si target on recording protons, deuterons and tritons in the energy range 40-70 MeV, 30-60 MeV and 30-50 MeV, respectively; isotope yields; momentum and angular momentum distributions of residual nuclei) are analyzed within the framework of the cascade-exciton model of nuclear reactions. Comparison is made with other up-to-date models of the process. The contributions of different pion absorption mechanisms and the relative role of different particle production mechanisms in these reactions are discussed. (author). 59 refs, 13 figs, 4 tabs

Semihard scattering unraveled from collective dynamics by two-pion azimuthal correlations in 158A GeV/c Pb+Au collisions.

Science.gov (United States)

Agakichiev, G; Appelshäuser, H; Baur, R; Bielcikova, J; Braun-Munzinger, P; Cherlin, A; Drees, A; Esumi, S I; Filimonov, K; Fraenkel, Z; Fuchs, Ch; Glässel, P; Hering, G; Huovinen, P; Lenkeit, B; Marín, A; Messer, F; Messer, M; Milosevic, J; Miśkowiec, D; Nix, O; Panebrattsev, Yu; Petrácek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Razin, S; Rehak, P; Sako, H; Saveljic, N; Schmitz, W; Shimansky, S; Socol, E; Specht, H J; Stachel, J; Tilsner, H; Tserruya, I; Voigt, C; Voloshin, S; Weber, C; Wessels, J P; Wurm, J P; Yurevich, V

2004-01-23

Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-p(T) pions (p(T)>1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb+Au collisions by the CERES experiment. Elliptic flow (v(2)) rises linearly with p(T) to a value of about 10% at 2 GeV/c. Beyond p(T) approximately 1.5 GeV/c, the slope decreases considerably, possibly indicating a saturation of v(2) at high p(T). Two-pion azimuthal anisotropies for p(T)>1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

Semihard scattering unraveled from collective dynamics by two-pion azimuthal correlations in 158A GeV/c Pb + Au collisions

CERN Document Server

Agakichiev, G; Baur, R; Bielcikova, J; Braun-Munzinger, P; Cherlin, A; Drees, A; Esumi, S I; Filimonov, K; Fraenkel, Zeev; Fuchs, C; Glässel, P; Hering, G; Huovinen, P; Lenkeit, B C; Marin, A; Messer, F; Messer, M; Milosevic, J; Miskowiec, D; Nix, O; Panebratsev, Yu A; Petracek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Razin, S; Rehak, P; Sako, H; Saveljic, N; Schmitz, W; Shimansky, S S; Socol, E; Specht, H J; Stachel, J; Tilsner, H; Tserruya, Itzhak; Voigt, C A; Voloshin, S A; Weber, C; Wessels, J P; Wurm, J P; Yurevich, V

2004-01-01

Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-$p_{T}$ pions ($p_{T}>$1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb + Au collisions by the CERES experiment. Elliptic flow ($v_{2}$) rises linearly with $p_{T}$ to a value of about 10% at 2 GeV/c. Beyond $p_{T} \\approx $1.5 Ge V/c, the slope decreases considerably, possibly indicating a saturation of $v_{2}$ at high $p_{T}$. Two-pion azimuthal anisotropies for $p_{T} >$1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

The quasi deuteron model for low energy pion absorption

International Nuclear Information System (INIS)

Gouweloos, M.

1986-01-01

In this thesis pion absorption in complex nuclei is studied in the quasi-deuteron model in which the pion is absorbed on a nucleon pair in the nucleus. The mechanism is studied in the low-energy domain since then the in-medium (pi→NN) operator turns out to be of simple character. In Ch. 2 and 3 this operator is constructed and analytical expressions are derived for (pi,NN) distributions in a plane wave impulse approximation for nuclei. The results turn out to be very useful for developing insight in the possibilities inherent in the QDM and the interpretation of the results in later chapters. Ch. 4 to 6 are devoted to the more realistic distorted wave calculations. In Ch. 4 the formal framework is presented and the calculational details are discussed. Ch.5 and 6 contain the comparison to stopped pion and in-flight data respectively. In Ch. 7 the main results are summarized. (Auth.)

Effect of resonance production and diffraction on the inclusive spectra of pions and protons in 19 GeV/c pn interactions

Energy Technology Data Exchange (ETDEWEB)

Baken, V.; Breivik, F.O.; Jacobsen, T. (Oslo Univ. (Norway). Fysisk Inst.)

1984-01-01

Bubble chamber data on pn interactions at 19 GeV/c are used to investigate the effects of nucleon diffraction and resonance production on the inclusive x- and psub(T)/sup 2/-distributions of protons and pions. We determine the differential distributions of p, ..pi../sup -/ and ..pi../sup +/ due to neutron and proton diffraction and similarly the distributions from the decay of the strong resonances ..delta../sup + +/(1232) and ..delta../sup -/(1232) and from rho/sup 0/(770). The x-distributions of the protons in the two c.m. hemispheres become quite similar when the effect of diffraction and ..delta../sup + +/ is subtracted. The psub(T)/sup 2/-distributions can then be described by a single exponential in the whole kinematic region. The net effect on the shapes of the x-distributions of the pions due to diffraction, ..delta../sup + +//..delta../sup -/ and rho/sup 0/ production is rather small. The separate effects of these processes on the particle ratio ..pi../sup -//..pi../sup +/ is investigated. By excluding the diffraction and ..delta../sup + +//..delta../sup -/ production, the strength of the low-psub(T)/sup 2/ component of the psub(T)/sup 2/-distributions of the pions is reduced, but it seems that diffraction and resonance production cannot account for all of this low-psub(T)/sup 2/ enhancement.

Low and intermediate energy pion-nucleus interactions in the cascade-exciton model

International Nuclear Information System (INIS)

Mashnik, S.G.

1993-01-01

A large variety of experimental data on pion-nucleus interactions in the bombarding energy range of 0-3000 MeV, on nucleon-induced pion production and on cumulative nucleon production, when a two-step process of pion production followed by absorption on nucleon pairs within a target is taken into account, are analyzed with the Cascade-Exciton Model of nuclear reactions.Comparison is made with other up-to-date models of these processes. The contributions of different pion absorption mechanisms and the relative role of different particle production mechanisms in these reactions are discussed

Twist-2 Light-Cone Pion Wave Function

OpenAIRE

Belyaev, V. M.; Johnson, Mikkel B.

1997-01-01

We present an analysis of the existing constraints for the twist-2 light-cone pion wave function. We find that existing information on the pion wave function does not exclude the possibility that the pion wave function attains its asymptotic form. New bounds on the parameters of the pion wave function are presented.

Pion inelastic scattering and the pion-nucleus effective interaction

International Nuclear Information System (INIS)

Carr, J.A.

1983-01-01

This work examines pion inelastic scattering with the primary purpose of gaining a better understanding of the properties of the pion-nucleus interaction. The main conclusion of the work is that an effective interaction which incorporates the most obvious theoretical corrections to the impulse approximation does a good job of explaining pion elastic and inelastic scattering from zero to 200 MeV without significant adjustments to the strength parameters of the force. Watson's multiple scattering theory is used to develop a theoretical interaction starting from the free pion-nucleon interaction. Elastic scattering was used to calibrate the isoscalar central interaction. It was found that the impulse approximation did poorly at low energy, while the multiple scattering corrections gave good agreement with all of the data after a few minor adjustments in the force. The distorted wave approximation for the inelastic transition matrix elements are evaluated for both natural and unnatural parity excitations. The isoscalar natural parity transitions are used to test the reaction theory, and it is found that the effective interaction calibrated by elastic scattering produces good agreement with the inelastic data. Calculations are also shown for other inelastic and charge exchange reactions. It appears that the isovector central interaction is reasonable, but the importance of medium corrections cannot be determined. The unnatural parity transitions are also reasonably described by the theoretical estimate of the spin-orbit interaction, but not enough systematic data exists to reach a firm conclusion

Systematics of pion double charge exchange

International Nuclear Information System (INIS)

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 π/ = 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

The nucleon's transversity and the photon's distribution amplitude probed in lepton pair photoproduction

Energy Technology Data Exchange (ETDEWEB)

Szymanowski, Lech [Soltan Institute for Nuclear Studies, Hoza 69, 00691, Warsaw (Poland); Pire, Bernard [Centre de Physique Theorique - CPHT, UMR 7644, Ecole Polytechnique, Bat. 6, RDC, F91128 Palaiseau Cedex (France)

2010-07-01

We describe a new way to access the chiral odd transversity parton distribution in the proton through the photoproduction of lepton pairs. The basic ingredient is the interference of the usual Bethe Heitler or Drell-Yan amplitudes with the amplitude of a process, where the photon couples to quarks through its chiral-odd distribution amplitude, which is normalized to the magnetic susceptibility of the QCD vacuum. A phenomenology of single and double spin observables emerges from the unusual features of this amplitude (Phys.Rev.Lett.103:072002,2009). (authors)

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.

Experimental study of pion-nucleus elastic scattering above the Δ-resonance with the SKS spectrometer

International Nuclear Information System (INIS)

Takahashi, Toshiyuki

1995-11-01

Differential cross sections of the pion elastic scattering in the GeV/c region were systematically measured by using a newly constructed superconducting kaon spectrometer at KEK. The pion incident momenta were 610, 710, 790, and 895 MeV/c for 12 C(π - , π - ) 12 C and 790 MeV/c for 208 Pb(π ± , π ± ) 208 Pb. We have obtained the cross sections with absolute normalization uncertainty of about 10%. The π - -p scattering data measured with a CH target agree well with the phase-shift calculations, which confirms the accuracy of the absolute values of the cross sections. The angular distributions of the differential cross sections for 12 C were compared with calculations by a first-order optical potential model. The calculation reproduces the data at forward scattering-angle regions except at 610 MeV/c, although it underestimates at large-angle region. The present data at 790 MeV/c are in between the BNL data at 800 MeV/c and the calculation, although our data are consistent with the BNL data within their systematic errors. The incident momentum dependence of σ total , σ R , and σ elastic , which were extracted by fitting the angular distributions, is different from that of the calculation with free π-N elementary amplitudes. It is well explained by taking account of Fermi motion. The 208 Pb data are well reproduced by the optical potential model. The root mean square radius of the neutron distribution has been deduced from π + and π - elastic scattering for the first time. Although the result has a model ambiguity, it agrees with that deduced from the proton elastic scattering. It is, however, smaller than the prediction of the relativistic Hartree calculation. (author). 55 refs

Experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies: Final report

International Nuclear Information System (INIS)

Burleson, G.R.

1987-01-01

We are applying for a three-year grant from the US Department of Energy to New Mexico State University to continue its support of our work on experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies, which has been carried out in collaboration with groups from various laboratories and universities. The nucleon-nucleon work is aimed at making measurements that will contribute to a determination of the isospin-zero amplitudes, as well as continuing our investigations of evidence for dibaryon resonances. It is based at the LAMPF accelerator in Los Alamos, New Mexico. Current and planned experiments include measurements of total cross-section differences in pure spin states and of spin parameters in neutron-proton scattering. The pion-nucleus work is aimed at improving our understanding both of the nature of the pion-nucleus interaction and of nuclear structure. It consists of two programs, one based at LAMPF and one based principally at the SIN laboratory in Switzerland. The LAMPF-based work involves studies of large-angle scattering, double-charge-exchange scattering, including measurements at a new energy range above 300 MeV, and a new program of experiments with polarized nuclear targets. The SIN-based work involves studies of quasielastic scattering and absorption, including experiments with a new large-acceptance detector system planned for construction there. We are requesting support to continue the LAMPF-based work at its current level and to expand the SIN-based work to allow for increased involvement in experiments with the new detector system. 57 refs

The two Josephson junction flux qubit with large tunneling amplitude

International Nuclear Information System (INIS)

Shnurkov, V.I.; Soroka, A.A.; Mel'nik, S.I.

2008-01-01

In this paper we discuss solid-state nanoelectronic realizations of Josephson flux qubits with large tunneling amplitude between the two macroscopic states. The latter can be controlled via the height and form of the potential barrier, which is determined by quantum-state engineering of the flux qubit circuit. The simplest circuit of the flux qubit is a superconducting loop interrupted by a Josephson nanoscale tunnel junction. The tunneling amplitude between two macroscopically different states can be increased substantially by engineering of the qubit circuit if the tunnel junction is replaced by a ScS contact. However, only Josephson tunnel junctions are particularly suitable for large-scale integration circuits and quantum detectors with present-day technology. To overcome this difficulty we consider here a flux qubit with high energy-level separation between the 'ground' and 'excited' states, consisting of a superconducting loop with two low-capacitance Josephson tunnel junctions in series. We demonstrate that for real parameters of resonant superposition between the two macroscopic states the tunneling amplitude can reach values greater than 1 K. Analytical results for the tunneling amplitude obtained within the semiclassical approximation by the instanton technique show good correlation with a numerical solution

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...

Azimuthal distributions of charged hadrons, pions, and kaons produced in deep-inelastic scattering off unpolarized protons and deuterons

Energy Technology Data Exchange (ETDEWEB)

Airapetian, A. [Giessen Univ. (Germany). Physikalisches Inst.; Michigan Univ., Ann Arbor, MI (United States). Randall Laboratory of Physics; Akopov, N. [Yerevan Physics Institute (Armenia); Akopov, Z. [DESY Hamburg (DE)] (and others)

2012-04-15

The azimuthal cos {phi} and cos 2{phi} modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the Hermes experiment. For the first time these modulations were determined in a four-dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins effects.

Intermediate-energy nuclear photoabsorption and the pion optical potential

International Nuclear Information System (INIS)

Christillin, P.

1984-01-01

Nuclear photoabsorption around the pion threshold is schematised as photoproduction of a pion which undergoes final-stae interaction with the nucleus, accounted for by the pion optical potential. It is shown that real pion photoproduction and exchange effects are naturally described by the same mechanism with a non-static pion. The complementarity of photoabsorption to pion physics and its usefulness in gaining new information about pion-nucleus dynamics are stressed. (author)

Charge amplitude distribution of the Gossip gaseous pixel detector

Energy Technology Data Exchange (ETDEWEB)

Blanco Carballo, V.M. [Twente University, Enschede (Netherlands); Chefdeville, M. [NIKHEF, P.B. 41882, 1009DB Amsterdam (Netherlands); Colas, P.; Giomataris, Y. [Saclay, Gif-sur-Yvette (France); Graaf, H. van der; Gromov, V. [NIKHEF, P.B. 41882, 1009DB Amsterdam (Netherlands); Hartjes, F. [NIKHEF, P.B. 41882, 1009DB Amsterdam (Netherlands)], E-mail: F.Hartjes@nikhef.nl; Kluit, R.; Koffeman, E. [NIKHEF, P.B. 41882, 1009DB Amsterdam (Netherlands); Salm, C.; Schmitz, J.; Smits, S.M. [Twente University, Enschede (Netherlands); Timmermans, J.; Visschers, J.L. [NIKHEF, P.B. 41882, 1009DB Amsterdam (Netherlands)

2007-12-11

The Gossip gaseous pixel detector is being developed for the detection of charged particles in extreme high radiation environments as foreseen close to the interaction point of the proposed super LHC. The detecting medium is a thin layer of gas. Because of the low density of this medium, only a few primary electron/ion pairs are created by the traversing particle. To get a detectable signal, the electrons drift towards a perforated metal foil (Micromegas) whereafter they are multiplied in a gas avalanche to provide a detectable signal. The gas avalanche occurs in the high field between the Micromegas and the pixel readout chip (ROC). Compared to a silicon pixel detector, Gossip features a low material budget and a low cooling power. An experiment using X-rays has indicated a possible high radiation tolerance exceeding 10{sup 16} hadrons/cm{sup 2}. The amplified charge signal has a broad amplitude distribution due to the limited statistics of the primary ionization and the statistical variation of the gas amplification. Therefore, some degree of inefficiency is inevitable. This study presents experimental results on the charge amplitude distribution for CO{sub 2}/DME (dimethyl-ether) and Ar/iC{sub 4}H{sub 10} mixtures. The measured curves were fitted with the outcome of a theoretical model. In the model, the physical Landau distribution is approximated by a Poisson distribution that is convoluted with the variation of the gas gain and the electronic noise. The value for the fraction of pedestal events is used for a direct calculation of the cluster density. For some gases, the measured cluster density is considerably lower than given in literature.

Charge amplitude distribution of the Gossip gaseous pixel detector

Science.gov (United States)

Blanco Carballo, V. M.; Chefdeville, M.; Colas, P.; Giomataris, Y.; van der Graaf, H.; Gromov, V.; Hartjes, F.; Kluit, R.; Koffeman, E.; Salm, C.; Schmitz, J.; Smits, S. M.; Timmermans, J.; Visschers, J. L.

2007-12-01

The Gossip gaseous pixel detector is being developed for the detection of charged particles in extreme high radiation environments as foreseen close to the interaction point of the proposed super LHC. The detecting medium is a thin layer of gas. Because of the low density of this medium, only a few primary electron/ion pairs are created by the traversing particle. To get a detectable signal, the electrons drift towards a perforated metal foil (Micromegas) whereafter they are multiplied in a gas avalanche to provide a detectable signal. The gas avalanche occurs in the high field between the Micromegas and the pixel readout chip (ROC). Compared to a silicon pixel detector, Gossip features a low material budget and a low cooling power. An experiment using X-rays has indicated a possible high radiation tolerance exceeding 10 16 hadrons/cm 2. The amplified charge signal has a broad amplitude distribution due to the limited statistics of the primary ionization and the statistical variation of the gas amplification. Therefore, some degree of inefficiency is inevitable. This study presents experimental results on the charge amplitude distribution for CO 2/DME (dimethyl-ether) and Ar/iC 4H 10 mixtures. The measured curves were fitted with the outcome of a theoretical model. In the model, the physical Landau distribution is approximated by a Poisson distribution that is convoluted with the variation of the gas gain and the electronic noise. The value for the fraction of pedestal events is used for a direct calculation of the cluster density. For some gases, the measured cluster density is considerably lower than given in literature.

Charge amplitude distribution of the Gossip gaseous pixel detector

International Nuclear Information System (INIS)

Blanco Carballo, V.M.; Chefdeville, M.; Colas, P.; Giomataris, Y.; Graaf, H. van der; Gromov, V.; Hartjes, F.; Kluit, R.; Koffeman, E.; Salm, C.; Schmitz, J.; Smits, S.M.; Timmermans, J.; Visschers, J.L.

2007-01-01

The Gossip gaseous pixel detector is being developed for the detection of charged particles in extreme high radiation environments as foreseen close to the interaction point of the proposed super LHC. The detecting medium is a thin layer of gas. Because of the low density of this medium, only a few primary electron/ion pairs are created by the traversing particle. To get a detectable signal, the electrons drift towards a perforated metal foil (Micromegas) whereafter they are multiplied in a gas avalanche to provide a detectable signal. The gas avalanche occurs in the high field between the Micromegas and the pixel readout chip (ROC). Compared to a silicon pixel detector, Gossip features a low material budget and a low cooling power. An experiment using X-rays has indicated a possible high radiation tolerance exceeding 10 16 hadrons/cm 2 . The amplified charge signal has a broad amplitude distribution due to the limited statistics of the primary ionization and the statistical variation of the gas amplification. Therefore, some degree of inefficiency is inevitable. This study presents experimental results on the charge amplitude distribution for CO 2 /DME (dimethyl-ether) and Ar/iC 4 H 10 mixtures. The measured curves were fitted with the outcome of a theoretical model. In the model, the physical Landau distribution is approximated by a Poisson distribution that is convoluted with the variation of the gas gain and the electronic noise. The value for the fraction of pedestal events is used for a direct calculation of the cluster density. For some gases, the measured cluster density is considerably lower than given in literature

Characteristic aspects of pion-condensed phases

International Nuclear Information System (INIS)

Takatsuka, Tatsuyuki; Tamagaki, Ryozo; Tatsumi, Toshitaka.

1993-01-01

Characteristic aspects of pion-condensed phases are described in a simple model, for the system involving only nucleons and pions which interact through the π-N P-wave interaction. We consider one typical version in each of three kinds of pion condensation; the one of neutral pions (π 0 ), the one of charged pions (π C ) and the combined one in which both the π 0 and π C condensations are coexistent. Emphasis is put on the description to clarify the novel structures of the nucleon system which are realized in the pion-condensed phases. At first, it is shown that the π 0 condensation is equivalent to the particular nucleonic phase realized by a structure change of the nucleon system, where the attractive first-order effect of the one-pion-exchange (OPE) tensor force is brought about coherently. The aspects of this phase are characterized by the layered structure with a specific spin-isospin order with one-dimensional localization (named the ALS structure in short), which provides the source function for the condensed π 0 field. We utilize both descriptions with use of fields and potentials for the π 0 condensation. Next, the π C condensation realized in neutron-rich matter is described by adopting a version of the traveling condensed wave. In this phase, the nucleonic structure becomes the Fermi gas consisting of quasi-neutrons described by a superposition of neutron and proton. In this sense the structure change of the nucleon system for the π C condensation is moderate, and the field description is suitable. Finally, we describe a coexistent pion condensation, in which both the π 0 and π C condensations coexist without interference in such a manner that the π C condensation develops in the ALS structure. The model adopted here provides us with the characteristic aspects of the pion-condensed phases persisting in the realistic situation, where other ingredients affecting the pion condensation are taken into account. (author)

On the imaginary part of the S-wave pion-nucleus optical potential

International Nuclear Information System (INIS)

Germond, J.F.; Lombard, R.J.

1991-01-01

The contribution of pion absorption to the imaginary part of the S-wave pion-nucleus optical potential is calculated with Slater determinantal antisymmetrized nuclear wave funtions, taking fully into accout the spin and isospin degrees of freedom. The potential obtained has an explicit dependence on the proton and neutron nuclear densities whose coefficients are directly related to the two-nucleon absorption coupling constants. The values of these coefficients extracted from mesic atoms data are in good agreement with those deduced from exclusive pion absorption experiments in 3 He, but larger than the predictions of the pion rescattering model. (orig.)

Relativistic quantum kinetic analysis of a pion--nucleon system

International Nuclear Information System (INIS)

Alonso, J.D.

1985-01-01

A relativistic plasma of nucleons interacting through pions via the usual isospin-invariant Yukawa coupling is analyzed in the framework of the covariant Wigner function technique. The method is manifestly covariant and the temperature effects are considered. The relativistic quantum BBGKY hierarchy for the pion--nucleon system is derived. By generalizing the Bogolioubov analysis of the classical BBGKY hierarchy a non-perturbative renormalizable method is elaborated which allows the solution of the kinetic problem in form of power series of two cluster parameters which measure the importance of correlations. In the lowest order of the cluster expansion (Hartree approximation of zero-order approximation) the quasi-nucleon Fock space is introduced, the fermion Wigner function in the thermodynamic equilibrium is obtained and the vacuum effects are renormalized. In this approximation the plasma behaves as a perfect Fermi gas of nucleons and antinucleons, but there exists an abnormal configuration with a uniform pion condensate which is unstable. In the next approximation (quadratic in the small parameters) the quasi-pion dispersion relation is obtained and the vacuum polarization tensor is renormalized. The quasi-pion rest-mass spectra (''plasma frequency'') and the effective-coupling behaviour as functions of the thermodynamic state are given. By estimating the size of the cluster parameters the self-consistency of the approximation scheme is proved. The quasi-pion Fock space is introduced and the quasi-pion equilibrium Wigner function is obtained. From these results the problem of the higher-order corrections to the Hartree thermodynamics is outlined

Universality of Generalized Parton Distributions in Light-Front Holographic QCD

Science.gov (United States)

de Téramond, Guy F.; Liu, Tianbo; Sufian, Raza Sabbir; Dosch, Hans Günter; Brodsky, Stanley J.; Deur, Alexandre; Hlfhs Collaboration

2018-05-01

The structure of generalized parton distributions is determined from light-front holographic QCD up to a universal reparametrization function w (x ) which incorporates Regge behavior at small x and inclusive counting rules at x →1 . A simple ansatz for w (x ) that fulfills these physics constraints with a single-parameter results in precise descriptions of both the nucleon and the pion quark distribution functions in comparison with global fits. The analytic structure of the amplitudes leads to a connection with the Veneziano model and hence to a nontrivial connection with Regge theory and the hadron spectrum.

Factorization, the light-cone distribution amplitude of the B-meson and the radiative decay $B \\to \\gamma l \

CERN Document Server

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.

Charge dependence of the pion-nucleon coupling constant

Directory of Open Access Journals (Sweden)

V. A. Babenko

2015-07-01

Full Text Available On the basis of the Yukawa potential we study the pion-nucleon coupling constants for the neutral and charged pions assuming that nuclear forces at low energies are mainly determined by the exchange of virtual pions. We obtain the charged pseudovector pion-nucleon coupling constant f2π± = 0.0804(7 by making the use of experimental low-energy scattering parameters for the singlet pp- and np-scattering, and also by use of the neutral pseudovector pion-nucleon coupling constant f2π0 = 0.0749(7. Corresponding value of the charged pseudoscalar pion-nucleon coupling constant g2π0 / 4π = 14.55(13 is also determined. This calculated value of the charged pseudoscalar pion-nucleon coupling constant is in fully agreement with the experimental constant g2π0 / 4π = 14.52(26 obtained by the Uppsala Neutron Research Group. Our results show considerable charge splitting of the pion-nucleon coupling constant.

Pion-nucleus scattering in the isobar formalism

International Nuclear Information System (INIS)

Moniz, E.J.

1978-06-01

Lectures on the isobar-hole model for pion reactions include the isobar as an explicit degree of freedom and the connection with a purely pion and nucleon system, the formalism and its relation to the pion optical potential, the extended schematic model for pion scattering, a simple spinless s-wave model, application to pion-oxygen 16 scattering and comparison with elastic scattering data. In this way the extent is shown to which microscopic treatment of the many-body dynamics explains the data and the extent to which additional physical input is required. Another test is the various inelastic processes. Inclusive reactions are briefly discussed. 37 references

Correlations and self-consistency in pion scattering. II

International Nuclear Information System (INIS)

Johnson, M.B.; Keister, B.D.

1978-01-01

In an attempt to overcome certain difficulties of summing higher order processes in pion multiple scattering theories, a new, systematic expansion for the interaction of a pion in nuclear matter is derived within the context of the Foldy-Walecka theory, incorporating nucleon-nucleon correlations and an idea of self-consistency. The first two orders in the expansion are evaluated as a function of the nonlocality range; the expansion appears to be rapidly converging, in contrast to expansion schemes previously examined. (Auth.)

Magnetic polarizability of pion

Energy Technology Data Exchange (ETDEWEB)

Luschevskaya, E.V., E-mail: luschevskaya@itep.ru [Institute for Theoretical and Experimental Physics, Bolshaia Cheremushkinskaia 25, 117218 Moscow (Russian Federation); School of Biomedicine, Far Eastern Federal University, 690950 Vladivostok (Russian Federation); Solovjeva, O.E., E-mail: olga.solovjeva@itep.ru [Institute for Theoretical and Experimental Physics, Bolshaia Cheremushkinskaia 25, 117218 Moscow (Russian Federation); Teryaev, O.V., E-mail: teryaev@theor.jinr.ru [Joint Institute for Nuclear Research, Dubna, 141980 (Russian Federation); National Research Nuclear University “MEPhI” (Moscow Engineering Physics Institute), Kashirskoe highway, 31, 115409 Moscow (Russian Federation)

2016-10-10

We explore the energy dependence of π mesons off the background Abelian magnetic field on the base of quenched SU(3) lattice gauge theory and calculate the magnetic dipole polarizability of charged and neutral pions for various lattice volumes and lattice spacings. The contribution of the magnetic hyperpolarizability to the neutral pion energy has been also found.

Pion-nucleon scattering in covariant baryon chiral perturbation theory with explicit Delta resonances

Energy Technology Data Exchange (ETDEWEB)

Yao, De-Liang [Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich, D-52425 Jülich (Germany); Siemens, D. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Bernard, V. [Groupe de Physique Théorique, Institut de Physique Nucléaire, UMR 8606,CNRS, University Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex (France); Epelbaum, E. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Gasparyan, A.M. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); SSC RF ITEP, Bolshaya Cheremushkinskaya 25, 117218 Moscow (Russian Federation); Gegelia, J. [Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich, D-52425 Jülich (Germany); Tbilisi State University, 0186 Tbilisi (Georgia); Krebs, H. [Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Meißner, Ulf-G. [Helmholtz Institut für Strahlen- und Kernphysik andBethe Center for Theoretical Physics, Universität Bonn, D-53115 Bonn (Germany); Institute for Advanced Simulation, Institut für Kernphysik and Jülich Center for Hadron Physics,Forschungszentrum Jülich, D-52425 Jülich (Germany)

2016-05-05

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.

Pions in the nuclear medium

International Nuclear Information System (INIS)

Chanfray, G.

1996-07-01

We discuss various aspects of pion physics in the nuclear medium. We first study s-wave pion-nucleus interaction in connection with chiral symmetry restoration and quark condensate in the nuclear medium. We then address the question of p-wave pion-nucleus interaction and collective pionic modes in nuclei and draw the consequences for in medium ππ correlations especially in the scalar-isoscalar channel. We finally discuss the modification of the rho meson mass spectrum at finite density and/or temperature in connection with relativistic heavy ion collisions

Two-Loop Scattering Amplitudes from the Riemann Sphere

CERN Document Server

Geyer, Yvonne; Monteiro, Ricardo; Tourkine, Piotr

2016-01-01

The scattering equations give striking formulae for massless scattering amplitudes at tree level and, as shown recently, at one loop. The progress at loop level was based on ambitwistor string theory, which naturally yields the scattering equations. We proposed that, for ambitwistor strings, the standard loop expansion in terms of the genus of the worldsheet is equivalent to an expansion in terms of nodes of a Riemann sphere, with the nodes carrying the loop momenta. In this paper, we show how to obtain two-loop scattering equations with the correct factorization properties. We adapt genus-two integrands from the ambitwistor string to the nodal Riemann sphere and show that these yield correct answers, by matching standard results for the four-point two-loop amplitudes of maximal supergravity and super-Yang-Mills theory. In the Yang-Mills case, this requires the loop analogue of the Parke-Taylor factor carrying the colour dependence, which includes non-planar contributions.

Radiation quality of beams of negative pions

International Nuclear Information System (INIS)

Dicello, J.F.; Brenner, D.J.

1981-01-01

As a negative pion stops in tissue, it attaches itself to an adjacent atom to form a mesonic atom. Subsequently, the wave function of the pion interacts with that of the nucleus and the pion is absorbed. Because the energy associated with the rest mass of the pion is greater than the separation energy of the nuclear particles, the nucleus disintegrates (pion star). In tissue, approximately 40 MeV goes into overcoming the binding energies; 20 MeV goes into kinetic energy of charged particles; 80 MeV goes into kinetic energy of neutrons. In cases where biological studies are performed with beams of negative pions, as much as 20% of the total absorbed dose in the treatment volume and about 50% of the high-LET dose (> 100 keV/μm) can result from neutrons. The degree of biological response and the variation of that response throughout the treatment volume can be altered by the neutron dose

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.)

Physics of the pion liquid

International Nuclear Information System (INIS)

Shuryak, E.V.

1990-01-01

Excited hadronic matter in the temperature interval T = 100-200 MeV is not an ideal pion gas, but ratehr a liquid, in which attractive interaction among particles plays an important role. Pion dispersion curve is in this case essentially modified by a kind of collective momentum-dependent potential, which becomes important as the quasipion comes to the boundary of the system. The author shows that these effects can provide an explanation for a number of recent experimental puzzles, in particular, for the observed copious production of soft pions and soft photons in high energy hadronic reactions

Physics of the pion liquid

International Nuclear Information System (INIS)

Shuryak, E.V.

1990-04-01

Excited hadronic matter in the temperature interval T = 100--200 MeV is not an ideal pion gas, but rather a liquid, in which attractive interaction among particles plays an important role. Pion dispersion curve is in this case essentially modified by a kind of collective momentum-dependent potential, which becomes important as the ''quasipion'' comes to the boundary of the system. We show that effects can provide and explanation for a number of recent experimental puzzles, in particular, for the observed copious production of soft pions and soft photons in high energy hadronic reactions. 31 refs., 13 figs

Experimental study on pion capture by hydrogen bound in molecules

International Nuclear Information System (INIS)

Horvath, D.; Aniol, K.A.; Entezami, F.; Measday, D.F.; Noble, A.J.; Stanislaus, S.; Virtue, C.J.

1988-08-01

An experiment was performed at TRIUMF to study the formation of pionic hydrogen atoms and molecules in solids, particularly in groups of organic molecules of slightly different structure in order to help further clarify the problem. The nuclear capture of pions by hydrogen was measured using the charge exchange of stopped pions. The coincident photons emitted by the decaying π 0 mesons were detected by TRIUMF's two large NaI spectrometers. New experimental results were obtained for the capture probability of stopped π - mesons in the nuclei of hydrogen atoms, chemically bound in molecules of some simple hydrides, acid anhydrides, and sugar isomers. A linear relation was found between pion capture in hydrogen and melting point in sugar isomers. The pion capture probability in acid anhydrides is fairly well described by a simple atomic capture model in which the capture probability on the hydrogen dramatically increases as the hydrogen atom is separated from the strongly electronegative C 2 O 3 group. Both effects are consistent with a correlation between pion capture and electron density on hydrogen atoms. (Author) (38 refs., 4 tabs., 7 figs.)

Reaction mechanism and nuclear correlations study by low energy pion double charge exchange

International Nuclear Information System (INIS)

Weinfeld, Z.

1993-06-01

In pion double-charge-exchange (DCX) reactions, a positive (negative) pion is incident on a nucleus and a negative (positive) pion emerges. These reactions are of fundamental interest since the process must involve at least two nucleons in order to conserve charge. Although two nucleon processes are present in many reactions they are usually masked by the dominant single nucleon processes. DCX is unique in that respect since it is a two nucleon process in lowest order and thus may be sensitive to two-nucleon correlations. Measurements of low energy pion double-charge-exchange reactions to the double-isobaric-analog-state (DIAS) and ground-state (GS) of the residual nucleus provide new means for studying nucleon-nucleon correlations in nuclei. At low energies (T π 7/2 shell at energies ranging from 25 to 65 MeV. Cross sections were measured on 42,44,48 Ca, 46,50 Ti and 54 Fe. The calcium isotopes make a good set of nuclei on which to study the effects of correlations in DCX reactions

Asymptotical behaviour of pion electromagnetic form factor in QCD

International Nuclear Information System (INIS)

Efremov, A.V.; Radyushkin, A.V.

1978-01-01

In the framework of the renormalizable quantum field theory a new approach is developed to the investigation of asymptotical behaviour of two-particle bound state electromagnetic form factor. It is shown that the behaviour of the pion EM form factor in quantum chromodynamics at sufficiently large momentum transfers is controlled by the short-distance dynamics only. The formula is obtained which expresses the asymptotical behaviour of the pion form factor in terms of the fundamental constants of the theory

A relativistic, meson exchange model of pion-nucleon scattering

International Nuclear Information System (INIS)

Pearces, B.C.; Jennings, B.K.

1990-06-01

A relativistic meson exchange approach to the pion-nucleon interaction is developed using a three-dimensional relativistic two-body propagator, and the results using different propagators are compared. The relativistic approach is able to describe low energy scattering up to 400 MeV above threshold, while preserving the soft pion theorems. The different propagators give similar results, as the form factors necessary to get a fit suppress much of the multiple scattering. (Author) (24 refs., 4 tabs., 6 figs.)

Pion-nucleon vertex function with one nucleon off shell

International Nuclear Information System (INIS)

Mizutani, T.; Rochus, P.

1979-01-01

The pion-nucleon vertex function with an off-mass-shell nucleon is obtained through sideways dispersion relations with the P 11 and S 11 pion-nucleon phase shifts as only input. Contrary to the recent calculation of Nutt and Shakin, we find that the proper and improper vertex functions behave quite differently, indicating the importance of the nucleon propagator dressing. In particular the proper vertex function is found to have two poles in the unphysical region

Measuring pion beta decay with high-energy pion beams

International Nuclear Information System (INIS)

McFarlane, W.K.; Hoffman, C.M.

1993-01-01

Improved measurements of the pion beta decay rate are possible with an intense high-energy pion beam. The rate for the decay π + → π 0 e + vε is predicted by the Standard Model (SM) to be R(π + → π 0 e + vε) = 0.3999±0.0005 s -1 . The best experimental number, obtained using in-flight decays, is R(π + → π 0 e + vε) = 0.394 ± 0.015 s -1 . A precise measurement would test the SM by testing the unitarity of the Cabibbo-Kobayashi-Maskawa matrix for which one analysis of the nuclear beta decay data has shown a 0.4% discrepancy. Several nuclear correction factors, needed for nuclear decay, are not present for pion beta decay, so that an experiment at the 0.2% level would be a significant one. Detailed study of possible designs will be needed, as well as extensive testing of components. The reduction of systematic errors to the 0.1% level can only be done over a period of years with a highly stable apparatus and beam. At a minimum, three years of occupancy of a beam line, with 800 hours per year, would be required

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.

Pion scattering to 8- stretched states in 60Ni

International Nuclear Information System (INIS)

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 π/ = 8/sup /minus// stretched states in 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 π + and 65/degree/ and 80/degree/ for π/sup /minus//. The analysis of the 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 π/sup /minus// and π + angular distributions are maximum, the ratios of π/sup /minus// to π + 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 ( 12 C, 14 C, 16 O, 28 Si, and 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

Effective pion--nucleon interaction in nuclear matter

International Nuclear Information System (INIS)

Celenza, L.S.; Liu, L.C.; Nutt, W.; Shakin, C.M.

1976-01-01

We discuss the modification of the interaction between a pion and a nucleon in the presence of an infinite medium of nucleons (nuclear matter). The theory presented here is covariant and is relevant to the calculation of the pion--nucleus optical potential. The specific effects considered are the modifications of the nucleon propagator due to the Pauli principle and the modification of the pion and nucleon propagators due to collisions with nucleons of the medium. We also discuss in detail the pion self-energy in the medium, paying close attention to off-shell effects. These latter effects are particularly important because of the rapid variation with energy of the fundamental pion--nucleon interaction. Numerical results are presented, the main feature being the appearance of a significant damping width for the (3, 3) resonance

Electron linac design for pion radiotherapy

International Nuclear Information System (INIS)

Loew, G.A.; Brown, K.L.; Miller, R.H.; Walz, D.R.

1977-03-01

The electron linac provides a straightforward, state-of-the-art method of producing the primary beam required for a hospital-based multiport pion radiotherapy facility for cancer treatment. The accelerator and associated beam transport system described are capable of generating an electron beam of about 250 kW and delivering it alternately to one of several pion generators and treatment areas. Each pion generator, a prototype of which now exists at the Stanford W. W. Hansen Laboratory, would contain a target for the electron beam and sixty separate superconducting magnet channels which focus the pions in the patient. The considerations which enter the design of a practical linac are presented together with a possible layout of a flexible beam transport system

Charged pions polarizability measurement at COMPASS

CERN Document Server

Guskov, A

2010-01-01

The pion electromagnetic structure can be probed in $\\pi^{−}+(A,Z)\\rightarrow\\pi^{-}+(A,Z)+\\gamma$ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric $(\\alpha_{\\pi})$ and the magnetic $(\\beta_{\\pi})$ polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of point-like pions with the measured cross section. The opportunity to measure pion polarizability via the Primakoff reaction at the COMPASS experiment was studied with $a$ $\\pi^{-}$ beam of 190 GeV during pilot run 2004. The obtained results were used for preparation of the new data taking which was performed in 2009.

Photo- and pion electroproduction in chiral effective field theory; Photo- und Elektropionproduktion in chiraler effektiver Feldtheorie

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.

Pion Rescattering in Nuclei

Energy Technology Data Exchange (ETDEWEB)

Paschos, E.A. [Institute for Physics, University of Dortmund, 44221 Dortmund (Germany); Schienbein, I. [Deutsches Elektronen Synchroton (DESY), 22603 Hamburg (Germany); Yu, J.-Y. [Institute for Physics, University of Dortmund, 44221 Dortmund (Germany)

2005-02-15

Nuclear corrections are presented for neutrino and electron induced reactions in a pedagogical manner. The formalism is demonstrated with numerical studies and shown to produce substantial corrections in channels where the pions have the same charge with the exchanged current. Two comparisons with available data show consistency of the model. Additional experimental results along these lines will improve the accuracy of the predictions and enhance the discovery potential of experiments.

Photon- and pion-induced reactions in the few body systems

International Nuclear Information System (INIS)

Laget, J.M.

1985-05-01

The study of the interplay of the degrees of freedom of the many nuclear system and the internal degrees of freedom of its constituents is reviewed. First nucleon-nucleon interaction mechanisms are recalled in relation to the interaction range. It appears that pion and photon induced reactions should provide two complementary ways to disentangle these various mechanisms. Most of pion and photon induced reactions, performed until now, can be understood in terms of nucleons, pions and deltas. But after a short description of the method of analysis of the reactions it is shown that this agreement is achieved at the price of the adjustment of two parameters (the πNN form factor and the rho-nucleon coupling contant) which may simulate more subtle short range effects. Then the relevance of the analysis of the same reactions in terms of quark degrees of freedom is discussed briefly

Sivers asymmetries for inclusive pion and kaon production in deep-inelastic scattering

International Nuclear Information System (INIS)

Ellis, John; Hwang, Dae Sung; Kotzinian, Aram

2009-01-01

We calculate the Sivers distribution functions induced by the final-state interaction due to one-gluon exchange in diquark models of a nucleon structure, treating the cases of scalar and axial-vector diquarks with both dipole and Gaussian form factors. We use these distribution functions to calculate the Sivers single-spin asymmetries for inclusive pion and kaon production in deep-inelastic scattering. We compare our calculations with the results of HERMES and COMPASS, finding good agreement for π + production at HERMES, and qualitative agreement for π 0 and K + production. Our predictions for pion and kaon production at COMPASS could be probed with increased statistics. The successful comparison of our calculations with the HERMES data constitutes prima facie evidence that the quarks in the nucleon have some orbital angular momentum in the infinite-momentum frame.

Sivers Asymmetries for Inclusive Pion and Kaon Production in Deep-Inelastic Scattering

CERN Document Server

Ellis, Jonathan Richard; Kotzinian, Aram

2009-01-01

We calculate the Sivers distribution functions induced by the final-state interaction due to one-gluon exchange in diquark models of nucleon structure, treating the cases of scalar and axial-vector diquarks with both dipole and Gaussian form factors. We use these distribution functions to calculate the Sivers single-spin asymmetries for inclusive pion and kaon production in deep-inelastic scattering. We compare our calculations with the results of HERMES and COMPASS, finding good agreement for pi+ production at HERMES, and qualitative agreement for pi0 and K+ production. Our predictions for pion and kaon production at COMPASS could be probed with increased statistics. The successful comparison of our calculations with the HERMES data constitutes prima facie evidence that the quarks in the nucleon have some orbital angular momentum in the infinite-momentum frame.

Nuclear potentials due to pion exchange

International Nuclear Information System (INIS)

Robillota, M.R.

1984-01-01

The two, three and four nucleon potentials due to the exchange of pions can be accurately calculated by means of chiral symmetry. The comparison of the dynamical content of these potentials allow us to understand the geometrical origin of the hierarchy existing among them. (Author) [pt

Renormalization and applications of baryon distribution amplitudes QCD

International Nuclear Information System (INIS)

Rohrwild, Juergen Holger

2009-01-01

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 * (1535) decay is discussed. Employing light-cone sum rule, the transition form factors can be directly related to the N * distribution amplitudes. (orig.)

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.)

Chiral behaviour of the pion decay constant in N{sub f}=2 QCD

Energy Technology Data Exchange (ETDEWEB)

Lottini, Stefano [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Collaboration: ALPHA Collaboration

2013-11-15

As increased statistics and new ensembles with light pions have become available within the CLS effort, we complete previous work by inspecting the chiral behaviour of the pion decay constant. We discuss the validity of Chiral Perturbation Theory ({chi}PT) and examine the results concerning the pion decay constant and the ensuing scale setting, the pion mass squared in units of the quark mass, and the ratio of decay constants f{sub K}=f{sub {pi}}; along the way, the relevant low-energy constants of SU(2) {chi}PT are estimated. All simulations were performed with two dynamical flavours of nonperturbatively O(a)-improved Wilson fermions, on volumes with m{sub {pi}}L{>=}4, pion masses{>=}192 MeV and lattice spacings down to 0.048 fm. Our error analysis takes into account the effect of slow modes on the autocorrelations.

Pion radiation therapy

International Nuclear Information System (INIS)

Kligerman, M.M.

1975-01-01

Results are summarized from studies on the relative biological effects as compared with x or γ radiation and OER of negative pi mesons produced by the Berkeley 184-inch synchrocyclotron or the NIMROD 7-GeV proton synchrocyclotron at the Rutherford High Energy Laboratory in England using cultured animal cells or Vicia faba cells as the test system. Preliminary results are reported from similar radiobiological studies at the Los Alamos Meson Physics Facility. The relative response of human tissues to peak pion irradiation was compared with 140 kV x rays in a single patient with multiple malignant melanoma by observing the acute response of the skin surrounding metastatic modules following exposure to either pions or x radiation. Color photographs of the irradiated areas made at least twice weekly and densitometry measurements and observations by radiation therapists indicated that maximum erythemia occurred during the fifth, sixth, or seventh week after the start of a schedule of fractionated exposure to 15 fractions over 19 elapsed days. X irradiation was delivered at a dose rate of 500 rads/min to modules to deliver 55, 66, or 75 percent of a skin surface dose of 5,200 rads and pion irradiation, at doses numerically 50 percent of the x ray dose, was delivered at a dose rate of 5 to 7 rads/min. Dose response curves were plotted. Results of histological examinations of skin samples taken 24 weeks following irradiation are reported. Results are discussed relative to the destruction of melanoma cells following pion or x ray treatment

Total and differential cross sections for pion production via coherent isobar and giant resonance formation in heavy-ion collisions

International Nuclear Information System (INIS)

Deutchman, P.A.; Norbury, J.W.; Townsend, L.W.

1985-01-01

A quantal many-body formalism is presented that investigates pion production through the coherent formation of a nucleonic isobar in the projectile and its subsequent decay to various pion charge states along with concomitant excitation of the target to a coherent spin-isospin giant resonance via a peripheral collision of relativistic heavy ions. Total cross sections as a function of the incident energy per nucleon and Lorentz-invariant differential cross sections as a function of pion energy and angle are calculated. It is shown that the pion angular distributions, in coincidence with the target giant resonance excitations, might provide a well-defined signature for these coherent processes

On the seagull effect in semi-inclusive distributions

International Nuclear Information System (INIS)

Ernst, W.

1978-01-01

Taking into account that pions contain two constituents, the semi-inclusive distributions are derived by information theory. From these distributions the psub(L)psub(T) correlations are especially calculated, the results are compared with experimental data

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.

Mechanism of pion absorption in complex nuclei

International Nuclear Information System (INIS)

Doss, K.G.N.; Wharton, W.R.

Basic geometrical arguments are used to analyze the A dependence of the total pion absorption cross section, the effective number of nucleons sharing the pion momentum and energy, and the proton yields from π + - and π - -induced reactions. The results are consistent with the pions penetrating some distance through the nuclear volume and annihilating on a pair of nucleons. 3 figures

Anomalous electrodynamics of neutral pion matter in strong magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Brauner, Tomáš [Department of Mathematics and Natural Sciences, University of Stavanger,N-4036 Stavanger (Norway); Kadam, Saurabh V. [Indian Institute of Science Education and Research (IISER),Pune 411008 (India)

2017-03-03

The ground state of quantum chromodynamics in sufficiently strong external magnetic fields and at moderate baryon chemical potential is a chiral soliton lattice (CSL) of neutral pions https://arxiv.org/abs/1609.05213. We investigate the interplay between the CSL structure and dynamical electromagnetic fields. Our main result is that in presence of the CSL background, the two physical photon polarizations and the neutral pion mix, giving rise to two gapped excitations and one gapless mode with a nonrelativistic dispersion relation. The nature of this mode depends on the direction of its propagation, interpolating between a circularly polarized electromagnetic wave https://www.doi.org/10.1103/PhysRevD.93.085036 and a neutral pion surface wave, which in turn arises from the spontaneously broken translation invariance. Quite remarkably, there is a neutral-pion-like mode that remains gapped even in the chiral limit, in seeming contradiction to the Goldstone theorem. Finally, we have a first look at the effect of thermal fluctuations of the CSL, showing that even the soft nonrelativistic excitation does not lead to the Landau-Peierls instability. However, it leads to an anomalous contribution to pressure that scales with temperature and magnetic field as T{sup 5/2}(B/f{sub π}){sup 3/2}.

The Adler-Weisberger and Goldberger-Miyazawa-Oehme sum rules as probes of constraints from analyticity and chiral symmetry in dynamical models for pion-nucleon scattering

International Nuclear Information System (INIS)

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 evaluating the sum-rule integrals with the calculated total cross section. The discrepancy between the results of the two methods provides a measure of the breaking of analyticity and chiral symmetry in the model. The contribution of the Δ resonance, including its dressing with meson loops, is discussed in some detail and found to be small

Joint resummation for pion wave function and pion transition form factor

Energy Technology Data Exchange (ETDEWEB)

Li, Hsiang-nan [Institute of Physics, Academia Sinica,Academia Rd., Taipei, Taiwan 115 (China); Department of Physics, National Cheng-Kung University,University Rd., Tainan, Taiwan 701 (China); Department of Physics, National Tsing-Hua University,Kuang-Fu Rd., Hsinchu, Taiwan 300 (China); Shen, Yue-Long [College of Information Science and Engineering, Ocean University of China,Songling Rd, Qingdao, Shandong 266100 (China); Wang, Yu-Ming [Institut für Theoretische Teilchenphysik und Kosmologie RWTH Aachen,Physikzentrum Otto-Blumenthal-Straße, D-52056 Aachen (Germany); Physik Department T31, Technische Universität München,James-Franck-Straße, D-85748 Garching (Germany)

2014-01-03

We construct an evolution equation for the pion wave function in the k{sub T} factorization formalism, whose solution sums the mixed logarithm ln xln k{sub T} to all orders, with x (k{sub T}) being a parton momentum fraction (transverse momentum). This joint resummation induces strong suppression of the pion wave function in the small x and large b regions, b being the impact parameter conjugate to k{sub T}, and improves the applicability of perturbative QCD to hard exclusive processes. The above effect is similar to those from the conventional threshold resummation for the double logarithm ln{sup 2} x and the conventional k{sub T} resummation for ln{sup 2} k{sub T}. Combining the evolution equation for the hard kernel, we are able to organize all large logarithms in the γ{sup ∗}π{sup 0}→γ scattering, and to establish a scheme-independent k{sub T} factorization formula. It will be shown that the significance of next-to-leading-order contributions and saturation behaviors of this process at high energy differ from those under the conventional resummations. It implies that QCD logarithmic corrections to a process must be handled appropriately, before its data are used to extract a hadron wave function. Our predictions for the involved pion transition form factor, derived under the joint resummation and the input of a non-asymptotic pion wave function with the second Gegenbauer moment a{sub 2}=0.05, match reasonably well the CLEO, BaBar, and Belle data.

Invariant potential for elastic pion--nucleus scattering

International Nuclear Information System (INIS)

Cammarata, J.B.; Banerjee, M.K.

1976-01-01

From the Wick-Dyson expansion of the exact propagator of a pion in the presence of a nucleus, an invariant potential for crossing symmetric elastic pion-nucleus scattering is obtained in terms of a series of pion-nucleon diagrams. The Chew-Low theory is used to develop a model in which the most important class of diagrams is effectively summed. Included in this model is the exclusion principle restriction on the pion-bound nucleon interaction, the effects of the binding of nucleons, a kinematic transformation of energy from the lab to the πN center of mass frame, and the Fermi motion and recoil of the target nucleons. From a numerical study of the effects of these processes on the π- 12 C total cross section, the relative importance of each is determined. Other processes contributing to the elastic scattering of pions not included in the present model are also discussed

Bumping structure of initial energy density distributions and peculiarities of pion spectra in A + A collisions

International Nuclear Information System (INIS)

Borysova, M.S.

2012-01-01

The effect of a fluctuating bumping structure of the initial conditions on spectra and the collective evolution of matter created in heavy-ion collisions in the frameworks of the Hydro-Kinetic Model is investigated. As motivated by the glasma-flux-tube scenario, the initial conditions are modeled by the set of four high energy-density tube-like fluctuations with longitudinally homogeneous structure within some space-rapidity region in a boost-invariant 2D geometry. It was found that the presence of transversally bumping tube-like fluctuations in initial conditions strongly affects the hydrodynamic evolution and leads to emergence of conspicuous structures in the calculated pion spectra. It was observed that the 4 tube initial configuration generates a four-peak structure in the final azimuthal distributions of one-particle spectra.

Near-threshold charged pion photoproduction from 13C

International Nuclear Information System (INIS)

LeRose, J.J.

1981-01-01

Differential cross sections to discrete final states have been measured for both positive and negative pion photo-production on 13 C at 90 0 in the lab at pion energies of 18, 29, and 41 MeV. Measurements were made using a fixed angle magnetic spectrometer located in the 14 0 area of the MIT Bates linear accelerator. Pions were detected using a 90 channel multi-wire proportional counter in the focal plane along with a backup array consisting of three 1/16'' thick plastic scintillator detectors and a 1/2'' thick Cerenkov detector. Positive pion photo-production cross sections were obtained for the excitation of the 3/2 - ground state and for the 3.45 MeV first excited state of 13 B. Negative pion photo-production cross sections were obtained for the excitation of the 1/2 - ground state, and the 3/2 to 3.51 MeV and 5/2 to 7.39 MeV excited states of 13 N. The measured positive pion photo-production ground state cross sections are in reasonable agreement wth theoretical calculations. However, there is a large discrepancy between the measured negative pion photoproduction ground state cross sections and the theoretical values. There are no theoretical calculations available for comparison with the excited state measurements in either positive or negative pion photoproduction on 13 C

Pion broadening and low-mass dilepton production

International Nuclear Information System (INIS)

Schulze, H.-J.; Blaschke, D.

2002-01-01

Mass and transverse momentum spectra of dileptons produced in Pb + Au (158 GeV/u) collisions within a pion annihilation model are determined. A fit to the data requires simultaneous mass reduction and broadening of the in-medium rho propagator. The introduction of a finite pion width, as required within self-consistent approaches to the interacting pion gas, further improves the agreement with the data

Can one distinguish τ-neutrinos from antineutrinos in neutral-current pion production processes?

International Nuclear Information System (INIS)

Hernandez, E.; Nieves, J.; Valverde, M.

2007-01-01

A potential way to distinguish τ-neutrinos from antineutrinos, below the τ-production threshold, but above the pion production one, is presented. It is based on the different behavior of the neutral-current pion production off the nucleon, depending on whether it is induced by neutrinos or antineutrinos. This procedure for distinguishing τ-neutrinos from antineutrinos neither relies on any nuclear model, nor it is affected by any nuclear effect (distortion of the outgoing nucleon waves, etc.). We show that neutrino-antineutrino asymmetries occur both in the totally integrated cross sections and in the pion azimuthal differential distributions. To define the asymmetries for the latter distributions we just rely on Lorentz-invariance. All these asymmetries are independent of the lepton family and can be experimentally measured by using electron or muon neutrinos, due to the lepton family universality of the neutral-current neutrino interaction. Nevertheless and to estimate their size, we have also used the chiral model of [E. Hernandez, J. Nieves, M. Valverde, hep-ph/0701149] at intermediate energies. Results are really significant since the differences between neutrino and antineutrino induced reactions are always large in all physical channels

Landau-Migdal parameters and pion condensation

Energy Technology Data Exchange (ETDEWEB)

Tatsumi, Toshitaka [Department of Physics, Kyoto Univ., Kyoto (Japan)

1999-08-01

The possibility of pion condensation, one of the long-standing issues in nuclear physics, is reexamined in the light of the recent experimental data on the giant Gamow-Teller resonance. The experimental result tells that the coupling of nucleon particle-hole states with {delta} isobar-hole states in the spin-isospin channel should be weaker than that previously believed. It, in turn, implies that nuclear matter has the making of pion condensation at low densities. The possibility and implications of pion condensation in the heavy-ion collisions and neutron stars should be seriously reconsidered. (author)

Factorization and pion form factor in QCD

International Nuclear Information System (INIS)

Efremov, A.V.; Radyushkin, A.V.

1979-01-01

The behaviour of the pion electromagnetic form factor (EMFF) in the framework of quantum chromodynamics (QCD) is discussed. Pion is considered to be a quark-antiquark bound state. It is proposed to use an OPE description of the bound state structure by matrix elements of certain local gauge-invariant operators. Short-distance quark interactions is proved using a direct analysis of perturbation theory in the α-parametric representation of the Feynman diagrams. It is shown that the short-distance parton picture privides a self-consistent description of the large Q 2 momentum behaviour of the pion EMFF in QCD. Pion EMFF asymptotics is expressed in terms of fu fundamental constants of the theory

The future IKO-PION-MUON-facility

International Nuclear Information System (INIS)

Goudsmit, P.F.A.; Arnold, H.; Dantzig, R. van; Konijn, J.

1975-09-01

Information is given on the pion and muon physics facility planned at the Institute for Nuclear Physics Research (IKO) with special notice of the fluxes of pions and muons expected at this facility, as well as on the structure of these secondary beams

Landau singularities and symbology: one- and two-loop MHV amplitudes in SYM theory

Energy Technology Data Exchange (ETDEWEB)

Dennen, Tristan; Spradlin, Marcus; Volovich, Anastasia [Department of Physics, Brown University,Providence RI 02912 (United States)

2016-03-14

We apply the Landau equations, whose solutions parameterize the locus of possible branch points, to the one- and two-loop Feynman integrals relevant to MHV amplitudes in planar N=4 super-Yang-Mills theory. We then identify which of the Landau singularities appear in the symbols of the amplitudes, and which do not. We observe that all of the symbol entries in the two-loop MHV amplitudes are already present as Landau singularities of one-loop pentagon integrals.

Landau singularities and symbology: one- and two-loop MHV amplitudes in SYM theory

International Nuclear Information System (INIS)

Dennen, Tristan; Spradlin, Marcus; Volovich, Anastasia

2016-01-01

We apply the Landau equations, whose solutions parameterize the locus of possible branch points, to the one- and two-loop Feynman integrals relevant to MHV amplitudes in planar N=4 super-Yang-Mills theory. We then identify which of the Landau singularities appear in the symbols of the amplitudes, and which do not. We observe that all of the symbol entries in the two-loop MHV amplitudes are already present as Landau singularities of one-loop pentagon integrals.

Quasi-pions with temperature dependent dispersion relation

International Nuclear Information System (INIS)

Gorenstein, M.I.

1995-01-01

We construct the procedure to calculate thermodynamical functions for a system of quasi-particles with temperature dependent dispersion relation. Two models for the hot quasi-pion system are considered to illustrate the importance of thermodynamical self consistency requirements. 8 refs., 9 figs

Study of elastic pion scattering from /sup 9/Be, /sup 28/Si, /sup 58/Ni, and /sup 208/Pb at 162 MeV. [Total and differential cross sections, scattering yields, scattering amplitudes

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.

The scattering of pions on polarized helium-three in the vicinity of delta resonance

International Nuclear Information System (INIS)

Braun, M.A.; Suslov, V.M.

1996-01-01

In the fixed-centers approximation the amplitude of the pion interaction with 3 H and 3 He is obtained. The N N interaction is neglected and for the πN interaction only the contribution of the P 33 state is included. The nuclear coordinate wave function was taken as a sum of Gaussian. The differential cross sections and asymmetries for elastic π -3 H(π +3 He) process at T π = 180 MeV are calculated. The results are compared with experimental data [ru

An investigation of the linear energy transfer distribution in a beam of negative pi-mesons

International Nuclear Information System (INIS)

Lewis, C.A.

1979-07-01

A review of the possible therapeutic advantages of negative pions is given and the more prolific of the dedicated facilities are described. The results are given of an examination of the microdosimetry of negative pion absorption in tissue through the measurement of event size spectra with proportional counters, and of the subsequent unfolding of these spectra in terms of LET distributions. The parameters LET and event size are discussed and methods of deriving LET distributions from event size measurements examined. Experiments with three tissue equivalent proportional counters of different geometry at the Rutherford Laboratory negative pion facility are described and the processing of the event size data is discussed. Fractional absorbed dose in LET distributions are presented for each of the counters at various positions of interest over the negative pion ionization profile. Quality Factors have been calculated from the data taken with the spherical counters and a Quality Factor of 5 is suggested for a negative pion beam. Results of measurements at two neutron facilities, a cyclotron neutron source and a 14 MeV neutron source, are also presented. Anomalies in the derived LET distributions are discussed. (UK)

Ratios of helicity amplitudes for exclusive ρ{sup 0} electroproduction on transversely polarized protons

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); Hulse, C. van [University of the Basque Country UPV/EHU, Department of Theoretical Physics, Bilbao (Spain); Ghent University, Department of Physics and Astronomy, Gent (Belgium); Yaschenko, S. [DESY, Hamburg (Germany); Universitaet Erlangen-Nuernberg, Physikalisches Institut, Erlangen (Germany); Collaboration: The HERMES Collaboration

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.)

Ratios of helicity amplitudes for exclusive ρ{sup 0} electroproduction on transversely polarized protons

Energy Technology Data Exchange (ETDEWEB)

Airapetian, A. [Giessen Univ. (Germany). 2. Physikalisches Inst.; Michigan Univ., Ann Arbor, MI (United States). Randall Lab. of Physics; Akopov, N. [Yerevan Physics Institute (Armenia); Akopov, Z. [DESY, Hamburg (Germany); Collaboration: HERMES Collaboration; and others

2017-06-13

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}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.

The pion mass: Looking for its origins

International Nuclear Information System (INIS)

Peccei, R.D.

1985-10-01

After explaining why pions are special excitations in QCD, I discuss how the pion mass reflects directly the dynamical scale of the strong interactions (Λsub(QCD)) and the scale of breaking of the weak interactions (Λsub(F)). To actually calculate the pion mass, however, requires understanding the origin of the quark masses and so I compare and contrast approaches to this latter problem, based on composite models and on superstrings. (orig.)

Double Δ-exchange contribution to pp-bar annihilation into three pions

International Nuclear Information System (INIS)

Betz, M.; Veit, E.A.; Haidenbauer, J.; Mull, V.

1999-01-01

Proton-antiproton annihilation into three uncorrelated pions is studied in a model based on both nucleon and Δ exchanges, with initial-state interactions described by the most complete version of the Juelich N N-bar model. The present work focuses in particular on the contribution of double Δ exchange, which had not been considered in previous work. The coupling constant at the ΔΔ π vertex, necessary to generate the double Δ-exchange amplitude, is fixed by reference to the SU (2) x SU(2) quark model. The effects of double Δ exchange are found to be rather small, though not negligible fort the π + π - π 0 channel. (author)

Funny hills in pion spectra from heavy-ion collisions

International Nuclear Information System (INIS)

Rasmussen, J.O.

1982-03-01

A discussion of some of the systematic features of the pion spectra in heavy-ions reactions is given. A discussion of the hills and valleys in heavy ion pion spectra that show up at the lower pion energies is given. The following topics are discussed: (1) three kinds of funny hills; (2) π - / + ratios near center of mass; (3) new Monte Carlo studies of charged pion spectra; and (4) pion orbiting about fireballs and Bose-Einstein behavior as explanation for the mid-rapidity P/sub perpendicular to/ approx. = 0.4 to 0.5 m/sub π/c hill

Nuclear-medium renormalization of the probabilities of the absorption of slow negative pions by nuclei

International Nuclear Information System (INIS)

Ivankov, Yu. V.; Kadmensky, S. G.

1997-01-01

Regions of admissible values of four constants determined by the ratios of the reduced probabilities of the absorption of slow negative pions by nucleon pairs in a nucleus to the analogous probabilities of absorption by free nucleon pairs are found from comparison of theoretical results and experimental data on the nuclear widths of the levels of π - mesic atoms and on the yields and energy distributions of nucleons and correlated nn and up pairs emitted in the absorption of slow negative pions by nuclei. It is concluded that some of these constants considerably deviate from unity. This suggests that a nuclear medium strongly affects hadron propagators or vertex functions determining negative-pion absorption by a nucleon pair at small distances

Negative pion irradiation of mammalian cells

International Nuclear Information System (INIS)

Dertinger, H.; Luecke-Huhle, C.; Schlag, H.; Weibezahn, K.F.

1976-01-01

Monolayers and spheroids of Chinese hamster cells (V79) were subjected to negative pion irradiation under aerobic conditions. R.b.e. values in the pion peak of 1.8 and 1.5 were obtained for monolayers and spheroids, respectively, whereas the r.b.e. for the plateau was found to be slightly higher than 1. In addition, it was observed that the higher resistance of the V79 spheroid cells than the monolayers to γ-irradiation is not diminished in the pion peak, suggesting that the underlying phenomenon of intercellular communication influences cell survival even after high-LET irradiation. (author)

Covariant density functional theory: The role of the pion

International Nuclear Information System (INIS)

Lalazissis, G. A.; Karatzikos, S.; Serra, M.; Otsuka, T.; Ring, P.

2009-01-01

We investigate the role of the pion in covariant density functional theory. Starting from conventional relativistic mean field (RMF) theory with a nonlinear coupling of the σ meson and without exchange terms we add pions with a pseudovector coupling to the nucleons in relativistic Hartree-Fock approximation. In order to take into account the change of the pion field in the nuclear medium the effective coupling constant of the pion is treated as a free parameter. It is found that the inclusion of the pion to this sort of density functionals does not destroy the overall description of the bulk properties by RMF. On the other hand, the noncentral contribution of the pion (tensor coupling) does have effects on single particle energies and on binding energies of certain nuclei.

Measurement of the charged-pion polarizability.

Science.gov (United States)

Adolph, C; Akhunzyanov, R; Alexeev, M G; Alexeev, G D; Amoroso, A; Andrieux, V; Anosov, V; Austregesilo, A; Badełek, 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; Büchele, 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; Dünnweber, W; Dziewiecki, M; Efremov, A; Elia, C; Eversheim, P D; Eyrich, W; Faessler, M; Ferrero, A; Filin, A; Finger, M; Finger, M; Fischer, H; Franco, C; du Fresne von Hohenesche, N; Friedrich, J M; Frolov, V; Gautheron, F; Gavrichtchouk, O P; Gerassimov, S; Geyer, R; Gnesi, I; Gobbo, B; Goertz, S; Gorzellik, M; Grabmüller, S; Grasso, A; Grube, B; Grussenmeyer, T; Guskov, A; Guthörl, T; Haas, F; von Harrach, D; Hahne, D; Hashimoto, R; Heinsius, F H; Herrmann, F; Hinterberger, F; Höppner, Ch; Horikawa, N; d'Hose, N; Huber, S; Ishimoto, S; Ivanov, A; Ivanshin, Yu; Iwata, T; Jahn, R; Jary, V; Jasinski, P; Jörg, 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; Königsmann, K; Konorov, I; Konstantinov, V F; Kotzinian, A M; Kouznetsov, O; Krämer, 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; Schlüter, T; Schmidt, K; Schmieden, H; Schönning, 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; ter Wolbeek, J; 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

2015-02-13

The COMPASS collaboration at CERN has investigated pion Compton scattering, π(-)γ→π(-)γ, at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π(-)Ni→π(-)γNi, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal 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 polarizability is determined to be α(π)=(2.0±0.6(stat)±0.7(syst))×10(-4)  fm(3) under the assumption α(π)=-β(π), which relates the electric and magnetic dipole polarizabilities. 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 found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty.

Off-shell two-particle scattering amplitude in the P-matrix approach

International Nuclear Information System (INIS)

Babenko, V.A.; Petrov, N.M.

1988-01-01

A generalization of the P-matrix approach which makes it possible to describe the interaction of two particles off the energy shell is proposed. Explicit separation in the wave function of a part corresponding to free motion yields a compact expression for the off-shell scattering amplitude and gives directly a method for separable expansion of the amplitude

The theory of hadronic systems

International Nuclear Information System (INIS)

Gibbs, W.R.

1995-01-01

This report briefly discusses progress on the following topics: isospin breaking in the pion-nucleon system; subthreshold amplitudes in the πN system; neutron-proton charge-exchange; transparency in pion production; energy dependence of pion DCX; direct capture of pions into deeply bound atomic states; knock out of secondary components in the nucleus; radii of neutron distributions in nuclei; the hadronic double scattering operator; pion scattering and charge exchange from polarized nuclei; pion absorption in nuclei; modification of nucleon structure in nuclei; and antiproton annihilation in nuclei

Electromagnetic properties of the pion as a composite Nambu-Goldstone boson

International Nuclear Information System (INIS)

Ito, H.; Buck, W.W.; Gross, F.

1992-01-01

Motivated by the Nambu--Jona-Lasinio model of light mesons, we introduce a covariant separable interaction to model the structure of relativistic quark-antiquark systems. The Schwinger-Dyson equation for the quark self-energy is solved analytically, generating a dynamical quark mass through spontaneous breaking of chiral symmetry, and yielding a pion which has zero mass in the chiral limit. The Bethe-Salpeter vertex function for this q bar q pion, which has a momentum distribution and composite structure associated with the interaction, is obtained analytically. Using this vertex function, and a similar one for the ρ meson, we calculate the electromagnetic observables of this composite Nambu-Goldstone boson, including effects from ρ-meson dominance processes. Our calculation takes the composite structure of the mesons into account. The ρ-meson effects are found to be very small in the pion charge form factor, but substantial in the charge radius. Using the model, predictions are made for γ * π 0 →γ and ρπγ transition form factors

Solar flare pion and neutron production

International Nuclear Information System (INIS)

Forrest, D.J.; Vestrand, W.T.

1992-01-01

During cycle 21, the Gamma Ray Spectrometer on SMM observed three large flares with clear evidence for pion decay gamma rays and high energy neutrons. Two of these had an extended emission phase. The emission observed in these extended phases were clearly different from those observed in the impulsive phase. Compared to the impulsive phase, the extended phase emissions were strongly deficient in electron bremsstrahlung relative to the nuclear line emission in the 1.0-7.0 MeV band and appeared to have a reduced energetic neutron to pion gamma ray emission in the >10 MeV band. These changes can be produced either by a strong hardening of the accelerated ion spectrum together with a relative decrease in the energetic electron spectrum, or by a pronounced change in the geometry of the particle spectrum downwards towards the photosphere. The authors review the observational evidence in terms of these two possibilities. A dramatic change in the energetic particle geometry appears to offer the simplest explanation. If true these two flares represent the first clear evidence of strong particle geometry effects within individual flares

Pion-nucleon vertex function and the Chew-Low model

International Nuclear Information System (INIS)

Nutt, W.T.

1977-01-01

We provide an interpretation of the cutoff function used in the Chew-Low theory of pion-nucleon scattering. It is shown that this function may be related to the pion-pion interaction which is not explicitly considered in the Chew-Low approach. Using a previously developed model for the pion-nucleon vertex function, we then perform a ''parameter-free'' Chew-Low calculation which predicts the P 33 resonance quite well

Gravitational wave from dark sector with dark pion

Energy Technology Data Exchange (ETDEWEB)

Tsumura, Koji [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Yamada, Masatoshi [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Yamaguchi, Yuya, E-mail: ko2@gauge.scphys.kyoto-u.ac.jp, E-mail: m.yamada@thphys.uni-heidelberg.de, E-mail: yy@particle.sci.hokudai.ac.jp [Department of Physics, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan)

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.

R.f.-induced steps in mutually coupled, two-dimensional distributed Josephson tunnel junctions

International Nuclear Information System (INIS)

Klein, U.; Dammschneider, P.

1991-01-01

This paper reports on the amplitudes of the current steps in the I-V characteristics of mutually coupled two-dimensional distributed Josephson tunnel junctions driven by microwaves. For this purpose we use a numerical computation algorithm based on a planar resonator model for the individual Josephson tunnel junctions to calculate the d.c. current density distribution. In addition to the fundamental microwave frequency, harmonic contents of the tunneling current are also considered. The lateral dimensions of the individual junctions are small compared to the microwave wavelength and the Josephson penetration depth, giving an almost constant current density distribution. Therefore, the coupled junctions can give much greater step amplitudes than a single junction with an equal tunneling area, because of their nonuniform current density distribution

Pion and kaon freezeout in NA44

International Nuclear Information System (INIS)

1994-01-01

The NA44 spectrometer is optimized for the study of single and two-particle particle spectra near mid-rapidity for transverse momenta below ∼ 1 GeV/c. A large fraction of all pairs in the spectrometer's acceptance are at low relative momenta, resulting in small statistical uncertainties on the extracted size parameters. In addition, the spectrometer's clean particle identification allows the authors to measure correlation functions for pions, kaons, and protons. This contribution will concentrate on the source size parameters determined from pion and kaon correlation functions. These size parameters will be compared to calculations from the RQMD event generator and also interpreted in the context of a hydrodynamic model. Finally, the measured single particle spectra will be examined from the viewpoint of hydrodynamics

A measurement of the pion charge radius

International Nuclear Information System (INIS)

Amendolia, S.R.; Badelek, B.; Batignani, G.; Bedeschi, F.; Bertolucci, E.; Bettoni, D.; Bosisio, L.; Bradaschia, C.; Dell'Orso, M.; Fidecaro, F.; Foa, L.; Focardi, E.; Giazotto, A.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Ristori, L.; Scribano, A.; Tonelli, G.; Codino, A.; Fabbri, F.L.; Laurelli, P.; Satta, L.; Spillantini, P.; Zallo, A.; Counihan, M.J.; Frank, S.G.F.; Harvey, J.; Storey, D.; Menasce, D.; Meroni, E.; Moroni, L.

1984-01-01

We report a measurement of the negative pion electromagnetic form factor in the range of space-like four-momentum transfer 0.014 2 2 . The measurement was made by the NA7 collaboration at the CERN SPS, by observing the interaction of 300 GeV pions with the electrons of a liquid hydrogen target. The form factor is fitted by a pole form with a pion radius of (rho 2 )sup(1/2) = 0.657 +- 0.012 fm. (orig.)

Fast pion production in exclusive neutrino processes

International Nuclear Information System (INIS)

Gershtein, S.S.; Komachenko, Yu.Ya.; Khlopov, M.Yu.

1980-01-01

Single pion production in exclusive neutrino reactions with small momentum transfer to nucleon, induced by neutrino scattering on virtual mesons (reggeons), is considered. The estimation of the contributions to process νA → μπA where A is a nucleon or the target nucleus made by various virtual mesons is presented. In the experimental investigation of such processes the contributions of different mesons may be singled out, thus providing information on the weak; meson-pion (reggeon-pion) transitions

Capture and transfer of pions in hydrogenous materials

International Nuclear Information System (INIS)

Armstrong, D.S.

1990-05-01

Pionic hydrogen is a short-lived exotic hydrogen isotope in which a negative pion replaces the atomic electron. The formation and subsequent interactions of pionic hydrogen are discussed, with emphasis on the process of pion transfer. Recent results using the pion charge-exchange reaction (π - , π 0 ) obtained at TRIUMF are reviewed. (Author) (35 refs., 3 tabs., 9 figs.)

DWPI: a computer program to calculate the inelastic scattering of pions from nuclei

Energy Technology Data Exchange (ETDEWEB)

Eisenstein, R A; Miller, G A [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA). Dept. of Physics

1976-02-01

Angular distributions for the inelastic scattering of pions are generated using the distorted wave impulse approximation (DWIA). The cross section for a given transition is calculated by summing a partial wave expansion. The T-matrix elements are calculated using distorted pion waves from the program PIRK, and therefore include elastic scattering to all orders. The excitation is treated in first order only. Several optical potentials and nuclear densities are available in the program. The transition form factor may be uncoupled from the ground-state density. Coulomb excitation, which interferes coherently with the strong interaction, is a program option.

A new version of DWPI (inelastic pion-nucleus scattering) to incorporate microscopic form factors and differing proton and neutron radii

International Nuclear Information System (INIS)

Funsten, H.O.

1979-01-01

This is a modification of the Eisenstein-Miller program for calculation of collective inelastic pion-nucleus differential cross sections using free π-N scattering amplitudes. This revision permits the additional use of microscopic (shell model) proton and neutron form factors. It also incorporates separate proton and neutron radii for the nuclear density rho(r) generating the distorted wave optical potential. (Auth.)

Pion scattering from very light nuclei

International Nuclear Information System (INIS)

Berman, B.

1993-01-01

Selected recent elastic and inelastic pion-scattering experiments on 3 H, 3 He, and 4 He will be reviewed. Particular attention will be given to multinucleon or cluster aspects of the data, and to possible comparisons with electron-scattering results. From elastic scattering from 3 H and 3 He at forward angles, one can extract the matter distribution of the paired neutrons in 3 H as well as that of the paired protons in 3 He. At backward angles, scattering from correlated nucleon pairs and/or two-step processes play an important role. For inelastic scattering, the momentum-transfer dependence of the cross section varies strongly with incident energy. Elastic scattering from a polarized 3 He target shows a strong asymmetry near 90 degrees. Elastic scattering from 4 He yields results which cannot be fitted with a simple optical model. An for inelastic scattering from 4 He, analysis of the data requires an important contribution from direct triton knockout

Understanding the amplitudes of noise correlation measurements

Science.gov (United States)

Tsai, Victor C.

2011-01-01

Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.

Relative amplitude preservation processing utilizing surface consistent amplitude correction. Part 4; Surface consistent amplitude correction wo mochiita sotai shinpuku hozon shori. 4

Energy Technology Data Exchange (ETDEWEB)

Saeki, T [Japan National Oil Corp., Tokyo (Japan). Technology Research Center

1997-10-22

Discussions were given on seismic exploration from the ground surface using the reflection method, for surface consistent amplitude correction from among effects imposed from the ground surface and a surface layer. Amplitude distribution on the reflection wave zone is complex. Therefore, items to be considered in making an analysis are multiple, such as estimation of spherical surface divergence effect and exponential attenuation effect, not only amplitude change through the surface layer. If all of these items are taken into consideration, burden of the work becomes excessive. As a method to solve this problem, utilization of amplitude in initial movement of a diffraction wave may be conceived. Distribution of the amplitude in initial movement of the diffraction wave shows a value relatively close to distribution of the vibration transmitting and receiving points. The reason for this is thought because characteristics of the vibration transmitting and receiving points related with waveline paths in the vicinity of the ground surface have no great difference both on the diffraction waves and on the reflection waves. The lecture described in this paper introduces an attempt of improving the efficiency of the surface consistent amplitude correction by utilizing the analysis of amplitude in initial movement of the diffraction wave. 4 refs., 2 figs.

Local integrands for two-loop all-plus Yang-Mills amplitudes

International Nuclear Information System (INIS)

Badger, Simon; Mogull, Gustav; Peraro, Tiziano

2016-01-01

We express the planar five- and six-gluon two-loop Yang-Mills amplitudes with all positive helicities in compact analytic form using D-dimensional local integrands that are free of spurious singularities. The integrand is fixed from on-shell tree amplitudes in six dimensions using D-dimensional generalised unitarity cuts. The resulting expressions are shown to have manifest infrared behaviour at the integrand level. We also find simple representations of the rational terms obtained after integration in 4−2ϵ dimensions.

Local integrands for two-loop all-plus Yang-Mills amplitudes

Energy Technology Data Exchange (ETDEWEB)

Badger, Simon; Mogull, Gustav; Peraro, Tiziano [Higgs Centre for Theoretical Physics, School of Physics and Astronomy,The University of Edinburgh, James Clerk Maxwell Building,Peter Guthrie Tait Road, Edinburgh EH9 3FD (United Kingdom)

2016-08-09

We express the planar five- and six-gluon two-loop Yang-Mills amplitudes with all positive helicities in compact analytic form using D-dimensional local integrands that are free of spurious singularities. The integrand is fixed from on-shell tree amplitudes in six dimensions using D-dimensional generalised unitarity cuts. The resulting expressions are shown to have manifest infrared behaviour at the integrand level. We also find simple representations of the rational terms obtained after integration in 4−2ϵ dimensions.

Two-level systems driven by large-amplitude fields

Science.gov (United States)

Nori, F.; Ashhab, S.; Johansson, J. R.; Zagoskin, A. M.

2009-03-01

We analyze the dynamics of a two-level system subject to driving by large-amplitude external fields, focusing on the resonance properties in the case of driving around the region of avoided level crossing. In particular, we consider three main questions that characterize resonance dynamics: (1) the resonance condition, (2) the frequency of the resulting oscillations on resonance, and (3) the width of the resonance. We identify the regions of validity of different approximations. In a large region of the parameter space, we use a geometric picture in order to obtain both a simple understanding of the dynamics and quantitative results. The geometric approach is obtained by dividing the evolution into discrete time steps, with each time step described by either a phase shift on the basis states or a coherent mixing process corresponding to a Landau-Zener crossing. We compare the results of the geometric picture with those of a rotating wave approximation. We also comment briefly on the prospects of employing strong driving as a useful tool to manipulate two-level systems. S. Ashhab, J.R. Johansson, A.M. Zagoskin, F. Nori, Two-level systems driven by large-amplitude fields, Phys. Rev. A 75, 063414 (2007). S. Ashhab et al, unpublished.

Remarks on the pion-nucleon σ-term

Science.gov (United States)

Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.

2016-09-01

The pion-nucleon σ-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 3σ 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.

Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy

Science.gov (United States)

Hellesen, C.; Mantsinen, M.; Conroy, S.; Ericsson, G.; Eriksson, J.; Kiptily, V. G.; Nabais, F.; Contributors, JET

2018-05-01

ICRF heating at the fundamental cyclotron frequency of a hydrogen minority ion species also gives rise to a partial power absorption by deuterium ions at their second harmonic resonance. This paper studies the deuterium distributions resulting from such 2nd harmonic heating at JET using neutron emission spectroscopy data from the time of flight spectrometer TOFOR. The fast deuterium distributions are obtained over the energy range 100 keV to 2 MeV. Specifically, we study how the fast deuterium distributions vary as ICRF heating is used alone as well as in combination with NBI heating. When comparing the different heating scenarios, we observed both a difference in the shapes of the distributions as well as in their absolute level. The differences are most pronounced below 0.5 MeV. Comparisons are made with corresponding distributions calculated with the code PION. We find a good agreement between the measured distributions and those calculated with PION, both in terms of their shapes as well as their amplitudes. However, we also identified a period with signs of an inverted fast ion distribution, which showed large disagreements between the modeled and measured results. Resonant interactions with tornado modes, i.e. core localized toroidal alfven eigenmodes (TAEs), are put forward as a possible explanation for the inverted distribution.

Goldberger-Treiman discrepancy and the momentum variation of the pion-nucleon form factor and pion decay constant

International Nuclear Information System (INIS)

Coon, S.A.; Scadron, M.D.

1981-01-01

We suggest that the observed 6% Goldberger-Treiman discrepancy is due in part to a 3% variation in the pion-nucleon form factor and in part due to a 3% variation in the pion decay form factor from q 2 =m/sub π/ 2 to q 2 =0

Large-q correlations from a Hubble-type pion source

International Nuclear Information System (INIS)

Barghouty, A.F.; Miller, J.; Frankel, K.A.

1993-01-01

In two-pion correlation measurements from relativistic nuclear collisions, the correlation function, C 2 (q), appears to exhibit an oscillatory structure at large (q ≥100 MeV/c) relative momentum. If real, this structure may have consequences for the determination of the space-time extent of the pion source. A qualitatively similar feature is seen in cellular automaton simulations of a Lorentz gas. It has been argued phenomenologically that the q-dependent oscillations can arise from an interplay between successive scattering probabilities and density variations of an exploding pion source. To further illustrate this interplay we consider a Hubble-type free expansion model for the source in which the density is time-folded from an initial Gaussian. This allows the source expansion to enter as a dynamical variable in the source density p[r(t); t] and thus C 2 , along with any signature of the interplay between scattering and source density

Study of the incident pion deflection in passing through atomic nucleus

International Nuclear Information System (INIS)

Strugalski, Z.; Pawlak, T.; Pluta, J.

1982-01-01

Pion-xenon nucleus collision events at 3.5 GeV/c momentum are studied in which the incident pion is deflected only, without particle production; the deflection is accompanied by emission of nucleons. The multiplicity of the protons emitted is a measure of the nuclear matter layer thickness passed by the pion. It can be concluded that: a) a definite simple relation exists between the pion deflection angle and the thickness of the nuclear matter layer traversed by this pion; b) the deflection angle of the incident pion increases in a definite manner with increasing the thickness of the nuclear matter layer traversed by this pion; c) the average kinetic energy, average longitudinal momentum and average transverse momentum of the protons emitted do not depend on the pion deflection angle

Microdosimetry of negative pions

International Nuclear Information System (INIS)

Amols, H.I.; Dicello, J.F.; Lane, T.F.

1976-01-01

The radiation quality of negative and positive pions of initial momentum 168MeV/c has been determined at eight different depths in a liquid phantom. The measurements were made with a 2.5cm diameter spherical proportional counter with Shonka A-150 neutron tissue equivalent plastic walls. The gas pressure in the sensitive volume was chosen to stimulate a diameter of 2μm in unit density material. Dose distributions as a function of lineal energy change slowly in the entrance and plateau regions with a dose mean lineal energy of 6-8keV/μm. Less than 3% of the dose is delivered in excess of 50keV/μm in this region. In the Bragg peak region the distributions change rapidly as a function of depth with the dose mean lineal energy increasing to 38keV/μm at the peak and to 57keV/μm just beyond the peak. On the basis of these microdosimetric data predictions of RBE and OER have been made with the use of both the theory of dual radiation action and also the delta ray theory of cell survival. The former has been used to predict biological response at low doses and the latter at high doses. A comparison is made between the two theories at intermediate doses. The results of these calculations are not inconsistant with recent biological data

A final state interaction model for K and eta decay into three pions

International Nuclear Information System (INIS)

Angus, A.G.

1973-07-01

The Khuri-Treiman model is adapted in a relativistic formalism with the electromagnetic mass differences of the pions in the final state taken into account to produce new predictions for the relative decay rates and the slope parameters of the four reactions K→3x and the two reactions eta→3x. The pion-pion interaction is investigated in terms of the N/D method and as well as the normal pure pole approximations for the N functions. The Khuri-Treiman equations are solved for the best solutions from both the pure pole and the mixed pole and cut models. (author)

Investigation of pion-nucleus interactions

International Nuclear Information System (INIS)

Moore, C.F.

1992-09-01

This report summarizes the work carried out by personnel from the University of Texas at Austin at the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF). The research activities involved experiments done with the Energetic Pion Channel and Spectrometer (EPICS), the Low Energy Pion Channel (LEP), the Pion and Particle Physics Channel (P 3 ), the High Resolution Spectrometer (HRS), and planning a new experimental program associated with the new high-resolution Neutral Meson Spectrometer (NMS) at LAMPF. A brief overview of work supported by this grant is given followed by an account of the study of the double giant resonances in pion double charge exchange on 51 V, 115 In, and 197 Au. This report contains a list of published papers and preprints, abstracts, and invited talks. These papers summarize experiments involving participants supported by this grant and indicate the work accomplished by these participants in this program of medium energy nuclear physics research. Lists of the most recent proposals on which we have participation at LAMPF, proposals which have been approved this past year to run as experiments, personnel who have participated in this research program are included. The research cited in this report is, in many cases, the collaborative effort of many groups associated with research at LAMPF

Experimental studies of pion-nucleus interactions at intermediate energies

International Nuclear Information System (INIS)

1991-01-01

This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting π 0 mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized 3 He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure

Azimuthal dependence of pion source radii in Pb + Au collisions at 158 A GeV

CERN Document Server

AUTHOR|(CDS)2073202; Andronic, A; Antonczyk, D; Appelshäuser, H; Belaga, V; Bielcikova, J; Braun-Munzinger, P; Busch, O; Cherlin, A; Damjanovic, S; Dietel, T; Dietrich, L; Drees, A; Dubitzky, W; Esumi, S I; Filimonov, K; Fomenko, K; Fraenkel, Zeev; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kalisky, M; Kniege, S; Kushpil, V; Maas, A; Marin, A; Milosevic, J; Miskowiec, D; Ortega, R; Panebratsev, Yu A; Petchenova, O; Petracek, V; Ploskon, M; Radomski, S; Rak, J; Ravinovich, I; Rehak, P; Sako, H; Schmitz, W; Schuchmann, S; Schükraft, J; Sedykh, S; Shimansky, S; Soualah, R; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, Itzhak; Tsiledakis, G; Wessels, J P; Wienold, T; Wurm, J P; Yurevich, S; Yurevich, V

2008-01-01

We present results of a two-pion correlation analysis performed with the Au+Pb collision data collected by the upgraded CERES experiment in the fall of 2000. The analysis was done in bins of the reaction centrality and the pion azimuthal emission angle with respect to the reaction plane. The pion source, deduced from the data, is slightly elongated in the direction perpendicular to the reaction plane, similarly as was observed at the AGS and at RHIC.

Disappearance of Anisotropic Intermittency in Large-amplitude MHD Turbulence and Its Comparison with Small-amplitude MHD Turbulence

Science.gov (United States)

Yang, Liping; Zhang, Lei; He, Jiansen; Tu, Chuanyi; Li, Shengtai; Wang, Xin; Wang, Linghua

2018-03-01

Multi-order structure functions in the solar wind are reported to display a monofractal scaling when sampled parallel to the local magnetic field and a multifractal scaling when measured perpendicularly. Whether and to what extent will the scaling anisotropy be weakened by the enhancement of turbulence amplitude relative to the background magnetic strength? In this study, based on two runs of the magnetohydrodynamic (MHD) turbulence simulation with different relative levels of turbulence amplitude, we investigate and compare the scaling of multi-order magnetic structure functions and magnetic probability distribution functions (PDFs) as well as their dependence on the direction of the local field. The numerical results show that for the case of large-amplitude MHD turbulence, the multi-order structure functions display a multifractal scaling at all angles to the local magnetic field, with PDFs deviating significantly from the Gaussian distribution and a flatness larger than 3 at all angles. In contrast, for the case of small-amplitude MHD turbulence, the multi-order structure functions and PDFs have different features in the quasi-parallel and quasi-perpendicular directions: a monofractal scaling and Gaussian-like distribution in the former, and a conversion of a monofractal scaling and Gaussian-like distribution into a multifractal scaling and non-Gaussian tail distribution in the latter. These results hint that when intermittencies are abundant and intense, the multifractal scaling in the structure functions can appear even if it is in the quasi-parallel direction; otherwise, the monofractal scaling in the structure functions remains even if it is in the quasi-perpendicular direction.

Renormalization and applications of baryon distribution amplitudes in QCD

International Nuclear Information System (INIS)

Rohrwild, Juergen Holger

2009-01-01

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 * (1535) decay is discussed. Employing light-cone sum rule, the transition form factors can be directly related to the N* 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.)

Wide angular range study of the reaction /sup 16/O( pi /sup -/, 2n) /sup 14/N with stopped pions

CERN Document Server

Bassalleck, B; Furic, M; Klotz, W D; Lewis, C W; Takeutchi, F; Ullrich, H

1980-01-01

A first kinematically complete investigation of the reaction /sup 16/O ( pi /sup -/, 2n)/sup 14/N with stopped pions has been performed at the CERN SC over a wide angular range. Measured distributions in excitation energy of the residual nucleus, recoil momentum, and angle between the two neutrons are presented. They are compared with theoretical predictions on two-hole states and with detailed calculations on the quasi-free two-nucleon absorption process. (34 refs).

Measurement of the Charged-Pion Polarizability

CERN Document Server

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.; Finger, M., 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.

2015-02-10

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...

Experimental studies of nucleon-nucleon and pion-nucleus interactions at intermediate energies: Annual progress report, 1988--1989

International Nuclear Information System (INIS)

1988-01-01

This report summarizes the work on experimental research in intermediate energy nuclear and particle physics carried out by New Mexico State University in 1988 under a grant from the US Department of Energy. The nucleon-nucleon research has involved studies of interactions between polarized neutrons and polarized protons. Its purpose is to help complete the determination of the nucleon-nucleon amplitudes at energies up to 800 MeV, as part of a program currently in progress at LAMPF, as well as to investigate the possibility of the existence of dibaryon resonances. The pion-nucleus research involves studies of this interaction in regions where it has not been adequately explored. These include experiments on elastic and double charge exchange scattering at energies above the /Delta/(1232) resonance, interactions with polarized nuclear targets, and investigations of pion absorption using a detector covering nearly the full solid angle region. 21 refs., 4 figs

High-energy pion beams: Problems and prospects

International Nuclear Information System (INIS)

Chrien, R.E.

1992-01-01

The investigation of relatively unexplored research areas with high energy pion beams requires new facilities. Presently existing meson factories such as LAMPF, TRIUMF and PSI provide insufficient pion fluxes above the 3,3 resonance region for access to topics such as strangeness production with the (π, K) reaction, baryon resonances, rare meson decays, and nuclear studies with penetrating pion beams. The problems and prospects of useful beams for these studies will be reviewed, both for existing facilities such as the AGS and KEK, and for possible future facilities like KAON and PILAC

Learning about nucleon resonances with pion photoproduction

International Nuclear Information System (INIS)

Walker, R.L.

1989-01-01

This chapter charts the discovery of nucleon resonances from pion-nucleon interactions. It was not until after the Albuquerque meeting in 1953 the experimentalists were able to persuade physicists about the existence of this phenomenon with the discovery of the P 33 resonance. The second and third resonances to be discovered, D 13 and F 15 , were seen as peaks in the total cross section for pion plus photoproduction, from 1956 onwards. Knowledge of pion-nucleon scattering has played an important role in the development of quark models. (UK)

A new determination of the pion mass

International Nuclear Information System (INIS)

Anagnastopoulos, D.; Belmiloud, D.; El-Khoury, P.; Indelicato, P.; Borchert, G.; Gorke, H.; Gotta, D.; Lenz, S.; Siems, T.; Daum, M.; Frosch, R.; Hauser, P.; Kirch, K.; Simons, L.M.

1996-01-01

Initial measurements concerning the feasibility of a new pion mass determination are described. In a first step, a high-resolution crystal spectrometer was coupled to a cyclotron trap which provides a high pion stopping density, sufficient to check predictions for the cascade process and to measure the stability of the apparatus. A comparison with the measured Cu K α fluorescence line resolves an ambiguity in the value of the pion mass. The preliminary result from this experiment is m π -=(139.57040±0.00045) MeV/c 2 . (orig.)

Development of a cooling system and vacuum chamber for the pion tracker for HADES

Energy Technology Data Exchange (ETDEWEB)

Wirth, Joana [Technische Univ. Muenchen, Garching (Germany). Excellence Cluster Universe; Collaboration: HADES-Collaboration

2013-07-01

One of the future experiments planned at SIS18 with the HADES spectrometer in GSI Darmstadt envisages the employment of pion beam colliding on LH2 or nuclear target. Due to the fact that secondary pion beam has high momentum spread, since the precise knowledge of pion momentum is mandatory to carry out the planned exclusive measurements, we have to measure the momentum for each individual pion. For this purpose our group is developing a pion beam tracking system, which consists of two silicon detectors. Both detectors are located in the beamline and therefore have to cope the high-intensity secondary beam. Cooling of a silicon detector strongly improves its radiation hardness and performance. It reduces the leakage current and thus the noise, which is important for the detection of MIPs like pions. We have designed and built a complete prototype system of vacuum chamber and detector cooling. With use of the Finite Element Method we simulated the mechanical and thermal properties of the prototype. The proposed poster shows the current status and performance of the cooling system for a test-detector, focusing on the reduction of the leakage current and the noise.

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.

The pion quasiparticle in the low-temperature phase of QCD

Directory of Open Access Journals (Sweden)

Brandt Bastian B.

2018-01-01

Full Text Available We extend our previous studies [PhysRevD.90.054509, PhysRevD.92.094510] of the pion quasiparticle in the low-temperature phase of two-flavor QCD with support from chiral effective theory. This includes the analysis performed on a finite temperature ensemble of size 20 × 643 at T ≈ 151MeV and a lighter zero-temperature pion mass mπ ≈ 185 MeV. Furthermore, we investigate the Gell-Mann–Oakes-Renner relation at finite temperature and the Dey-Eletsky-Ioffe mixing theorem at finite quark mass.

Incorporating pion effects into the naive quark model

International Nuclear Information System (INIS)

Nogami, Y.; Ohtuska, N.

1982-01-01

A hybrid of the naive nonrelativistic quark model and the Chew-Low model is proposed. The pion is treated as an elementary particle which interacts with the ''bare baryon'' or ''baryon core'' via the Chew-Low interaction. The baryon core, which is the source of the pion interaction, is described by the naive nonrelativistic quark model. It turns out that the baryon-core radius has to be as large as 0.8 fm, and consequently the cutoff momentum Λ for the pion interaction is < or approx. =3m/sub π/, m/sub π/ being the pion mass. Because of this small Λ (as compared with Λapprox. nucleon mass in the old Chew-Low model) the effects of the pion cloud are strongly suppressed. The baryon masses, baryon magnetic moments, and the nucleon charge radii can be reproduced quite well. However, we found it singularly difficult to fit the axial-vector weak decay constant g/sub A/

Precise measurements of beam spin asymmetries in semi-inclusive π0 production

Science.gov (United States)

Aghasyan, M.; Avakian, H.; Rossi, P.; De Sanctis, E.; Hasch, D.; Mirazita, M.; Adikaram, D.; Amaryan, M. J.; Anghinolfi, M.; Baghdasaryan, H.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Bennett, R. P.; Biselli, A. S.; Branford, D.; Briscoe, W. J.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Chandavar, S.; Cole, P. L.; Collins, P.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Daniel, A.; Dashyan, N.; De Vita, R.; Deur, A.; Dey, B.; Dickson, R.; Djalali, C.; Dodge, G. E.; Doughty, D.; Dupre, R.; Egiyan, H.; El Alaoui, A.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fradi, A.; Gabrielyan, M. Y.; Garçon, M.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Graham, L.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guler, N.; Guo, L.; Hafidi, K.; Hanretty, C.; Hicks, K.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Isupov, E. L.; Jawalkar, S. S.; Jenkins, D.; Jo, H. S.; Joo, K.; Keller, D.; Khandaker, M.; Khetarpal, P.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Kubarovsky, V.; Kuhn, S. E.; Kuleshov, S. V.; Kuznetsov, V.; Kvaltine, N. D.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McAndrew, J.; McKinnon, B.; Meyer, C. A.; Micherdzinska, A. M.; Mokeev, V.; Moreno, B.; Moutarde, H.; Munevar, E.; Nadel-Turonski, P.; Ni, A.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Paolone, M.; Pappalardo, L.; Paremuzyan, R.; Park, K.; Park, S.; Pasyuk, E.; Pereira, S. Anefalos; Phelps, E.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Raue, B. A.; Ricco, G.; Rimal, D.; Ripani, M.; Rosner, G.; Sabatié, F.; Saini, M. S.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Sharabian, Y. G.; Smith, G. D.; Sober, D. I.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Strakovsky, I.; Strauch, S.; Taiuti, M.; Tang, W.; Taylor, C. E.; Tkachenko, S.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Watts, D.; Weinstein, L. B.; Weygand, D. P.; Wood, M. H.; Zana, L.; Zhang, J.; Zhao, B.; Zhao, Z. W.

2011-10-01

We present studies of single-spin asymmetries for neutral pion electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV polarized electrons from an unpolarized hydrogen target, using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. A substantial sinϕh amplitude has been measured in the distribution of the cross section asymmetry as a function of the azimuthal angle ϕh of the produced neutral pion. The dependence of this amplitude on Bjorken x and on the pion transverse momentum is extracted with significantly higher precision than previous data and is compared to model calculations.

Exclusive vector meson production with leading neutrons in a saturation model for the dipole amplitude in mixed space

Science.gov (United States)

Amaral, J. T.; Becker, V. M.

2018-05-01

We investigate ρ vector meson production in e p collisions at HERA with leading neutrons in the dipole formalism. The interaction of the dipole and the pion is described in a mixed-space approach, in which the dipole-pion scattering amplitude is given by the Marquet-Peschanski-Soyez saturation model, which is based on the traveling wave solutions of the nonlinear Balitsky-Kovchegov equation. We estimate the magnitude of the absorption effects and compare our results with a previous analysis of the same process in full coordinate space. In contrast with this approach, the present study leads to absorption K factors in the range of those predicted by previous theoretical studies on semi-inclusive processes.

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.

Modified three-pole VMD model with two-branch-point analytic structure and approved asymptotic behaviour for the pion electromagnetic form factor

International Nuclear Information System (INIS)

Dubnicka, S.; Furdik, I.; Meshcheryakov, V.A.

1987-01-01

A modification of three-pole VMD model for electromagnetic pion form factor was carried out, first by means of its transformation into the pion c.m. momentum variable and subsequently by using the inverse Zhukovsky transformation into another variable. In such a procedure a common normalized factor for all three vector mesons, ρ(770), ρ'(1250) and ρ''(1600), is singled out, by means of which it is possible to settle a specific freedom in the choice of the pion form factor asymptotic behaviour. An explicit incorporation of nonzero vector meson widths creates a real analytic model, defined on the four-sheeted Riemann surface. It includes inelastic contributions effectively, depends just on the parameters with a clear physical meaning, conserves the normalization of the original VMD parametrization, and provides a perfect fit of all existing pion form factor data, in which all parameters of the model are determined and the presence of ρ'(1250) in e + e - → π + π - is again established

Construction of two-dimensional Schrodinger operator with given scattering amplitude at fixed energy

International Nuclear Information System (INIS)

Novikov, R.G.

1986-01-01

The classical necessary properties of the scattering amplitude (reciprocity and unitarity) are, provided its L 2 norm is small, sufficient for the existence of a two-dimensional Schrodinger operator with the given scattering amplitude at fixed energy

Low energy pion detection by a silicon surface barrier telescope

International Nuclear Information System (INIS)

Sealock, R.M.; Caplan, H.S.; Leung, M.K.

1978-01-01

Four telescopes of three (2-ΔE, 1-E) silicon surface barrier detectors each, mounted in the focal plane of a magnetic spectrometer, have been used to detect positive pions in the energy range from 4.7-17.9 MeV and negative pions from 14.1-17.9 MeV. Positive pions from 4.7-12.7 MeV were stopped in the third detector while positive and negative pions from 14.1-17.9 MeV were detected in transmission. For energies greater than 7.4 MeV aluminum moderators were placed in front of the first detector to degrade the pion energy. Energy spectra show well resolved pion peaks with extremely low background. Double differential cross sections for the 12 C(e,π + ) 12 B,e' reaction have been measured. (Auth.)

Analyticity properties of two-body helicity amplitudes; Proprietes d'analyticite des amplitudes d'helicite a deux corps

Energy Technology Data Exchange (ETDEWEB)

Navelet-Noualhier, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-06-15

Helicity amplitudes are expressed via the spinor amplitudes in terms of the Joos invariant which have been shown by Williams to be free from kinematical singularities. This procedure allows to analyze the kinematical singularities of helicity amplitudes and separate them out, which results into the definition of regularized helicity amplitudes. A crossing matrix for helicity amplitudes, is written down, corresponding to the continuation path used to cross spinor amplitudes. We verify explicitly that the corresponding crossing matrix for regularized helicity amplitudes is uniform as it should be. Kinematical constraints which generalize, to the case of arbitrary spins and masses, relations which must hold between helicity amplitudes at some values of the energy variable in {pi}N {yields} {pi}N, {pi}{pi} {yields} NN-bar and NN-bar {yields} NN-bar reactions, appear as a consequence of the existence of poles in the crossing matrix between regularized helicity amplitudes. An english version of this work has been written with G. Cohen-Tannoudji and A. Morel and submitted for publication to Annals of Physics. (author) [French] Les amplitudes d'helicite pour une reaction a deux corps sont exprimees, par l'intermediaire des amplitudes spinorielles, en fonction d'amplitudes invariantes de Joos qui sont, comme l'a montre Williams, sans singularites cinematiques. Ce procede nous permet d'analyser puis d'eliminer les singularites cinematiques des amplitudes d'helicite. Ceci nous conduit a la definition d'amplitudes d'helicite 'regularisees'. Une relation de 'croisement' entre amplitudes d'helicite est ecrite; elle realise leur prolongement analytique le long du chemin utilise pour 'croiser' les amplitudes spinorielles. Nous verifions que les elements de la matrice de croisement entre amplitudes d'helicite 'regularisees' sont bien uniformes. Les contraintes cinematiques qui generalisent, au cas de masses et de spins arbitraires, les relations obtenues dans les reactions {pi

Characteristics of the pion production and nucleon emission processes in pion-carbon nuclear collisions at 40 GeV/.c

International Nuclear Information System (INIS)

Strugalski, Z.; Sultanov, M.

1992-01-01

Experimental data on pion-carbon nucleus collisions are presented. The momentum and energy spectra of protons emitted from the target nucleus do not depend on the intensity of the pion production in the collisions. 6 refs.; 12 figs.; 12 tabs

Some long-term effects of negative pions in mice exposed to partial body irradiation

International Nuclear Information System (INIS)

Coggle, J.E.

1977-01-01

The long-term effects of partial body exposure of one-day-old mice given either 60 Co γ rays or negative pions have been studied. Both radiations produced considerable life-shortening; for pions 6.8 +- 1.5% of life was lost per 100 rad and for γ rays the value was 5.7 +- 0.5% per 100 rad. The RBE of pions for ten weeks of life-shortening was about 1.3 compared with 60 Co γ rays, although at lower doses the RBE may be higher reaching about two for six weeks of life-shortening. The incidence rate of tumours at any particular age was greater in mice irradiated with pions at the peak and in those given higher doses of γ rays than in the controls. (author)

A complete two-loop, five-gluon helicity amplitude in Yang-Mills theory

International Nuclear Information System (INIS)

Badger, Simon; Mogull, Gustav; Ochirov, Alexander; O’Connell, Donal

2015-01-01

We compute the integrand of the full-colour, two-loop, five-gluon scattering amplitude in pure Yang-Mills theory with all helicities positive, using generalized unitarity cuts. Tree-level BCJ relations, satisfied by amplitudes appearing in the cuts, allow us to deduce all the necessary non-planar information for the full-colour amplitude from known planar data. We present our result in terms of irreducible numerators, with colour factors derived from the multi-peripheral colour decomposition. Finally, the leading soft divergences are checked to reproduce the expected infrared behaviour.

A complete two-loop, five-gluon helicity amplitude in Yang-Mills theory

Energy Technology Data Exchange (ETDEWEB)

Badger, Simon; Mogull, Gustav; Ochirov, Alexander [Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); O’Connell, Donal [Higgs Centre for Theoretical Physics, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106-4030 (United States)

2015-10-09

We compute the integrand of the full-colour, two-loop, five-gluon scattering amplitude in pure Yang-Mills theory with all helicities positive, using generalized unitarity cuts. Tree-level BCJ relations, satisfied by amplitudes appearing in the cuts, allow us to deduce all the necessary non-planar information for the full-colour amplitude from known planar data. We present our result in terms of irreducible numerators, with colour factors derived from the multi-peripheral colour decomposition. Finally, the leading soft divergences are checked to reproduce the expected infrared behaviour.

Investigation of Compton effect on π-meson and charged pion polarizability

International Nuclear Information System (INIS)

Antipov, Yu.M.; Batarin, V.A.; Bezzubov, V.A.

1986-01-01

The results of an experiment aimed at the study of the 40 GeV/c pion radiative scattering on nuclei at small momentum transfers are presented. Compton effect on the pion was investigated and the charged pion polarizability was measured. The pion Compton-effect cross section dependence on the incident photon energy ω' 1 (rest pion frame) was measured in the 100 - 600 MeV range. The polarizability of charged pion from the analysis of Compton-effect events has been found to be β π =-α π =(-6.9 ± 1.4 stat. ± 1.2 syst. )x10 -43 cm 3 and the sun of pion electrical α π and magnetic β π polarizability has been estimated to be in agreement with theoretical predictions: α π +β π ≅ 0

Status of PILAC: A pion linac facility for 1-GeV pion physics at LAMPF

International Nuclear Information System (INIS)

Thiessen, H.A.

1990-01-01

A Pion Linac (PILAC) is being designed for LAMPF. Together with its high resolution beam line and spectrometer, the system is optimized to provide 10 9 pions per second on target and 200-keV resolution for the (π + ,K + ) reaction at 920, MeV. There will also be an achromatic beam line capable of utilizing the maximum energy available, thus opening up the possibility of a broad experimental program as is being discussed at this workshop. 12 figs

Pion electroproduction at threshold on the nucleon. Contribution to the measurement of the nucleon form factor

International Nuclear Information System (INIS)

Duval, M.A.

1989-11-01

A pion electroproduction experiment is discussed. The experiment is carried out at threshold on the proton, at the Saclay Linear Accelerator. The scattered electron and the produced pion are detected in coincidence. The aim of the investigation is to measure the nucleon axial form factor. Theoretical concepts and previous experiments are reviewed. The experimental set-up is described, in particular the new pion arm and the trigger simulation. The preliminary analysis of six kinematical points at the momentum transfer of two inverse fermis squared shows the feasibility of the experiment. The pions detection and their identification are satisfactory and allow measurements to be performed [fr

Chiral pion dynamics for spherical nucleon bags

International Nuclear Information System (INIS)

Vento, V.; Rho, M.; Nyman, E.M.; Jun, J.H.; Brown, G.E.; CEA Centre d'Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette

1980-01-01

A chirally symmetric quark-bag model for the nucleon is obtained by introducing an explicit, classical, pion field exterior to the bag. The coupling at the bag surface is determined by the requirement of a conserved axial-vector current. The pion field satisfies equations of motion corresponding to the non-linear sigma-model. We study on this paper the simplified case where the bag and the pion field are spherically symmetric. Corrections due to gluon exchange between the quarks are ignored along with other interactions which split the N- and Δ-masses. The equations of motion for the pion field are solved and we find a substantial pion pressure at the bag surface, along with an attractive contribution to the nucleon self-energy. The total energy of the system, bag plus meson cloud, turns out to be approximately Msub(n)c 2 for a wide range of bag radii, from 1.5 fm down to about 0.5 fm. Introduction of a form factor for the pion would extend the range of possible radii to even smaller values. We propose that the bag with the smallest allowed radius be identified with the 'little bag' discussed before. One surprising result of the paper is that as long as one restricts to spherically symmetric bags, restoring chiral symmetry to the bag model makes the axial-vector current coupling constant gsub(A) to be always too large compared with the experimental value for any bag radius, suggesting a deviation from spherical symmetry for the intrinsic bag wave functions of the 'ground-state' hadrons. (orig.)

Strangeness production with protons and pions

International Nuclear Information System (INIS)

Dover, C.B.

1993-01-01

We discuss the spectrum of physics questions related to strangeness which could be addressed with intense beams of protons and pions in the few GeV region. We focus on various aspects of strangeness production, including hyperon production in pp collisions, studies of hyperon-nucleon scattering, production of hypernuclei in proton and pion-nucleus collisions, and spin phenomena in hypernuclei

Neutral meson measurement using different neutral pion reconstruction techniques in ALICE in pp collisions at $\\sqrt s = 7$ TeV

CERN Document Server

Jonas, Florian

2017-01-01

In this analysis, which is carried out as part of a summer student project, the $\\omega$ and $\\eta$ mesons are measured in pp collisions at $\\sqrt s = 7$ TeV using ALICE's two calorimeters PHOS and EMCal, the so called Photon Conversion Method (PCM) and two hybrid methods that combine one photon that was reconstructed with PCM and the other photon measured with the different calorimeters for neutral pion reconstruction. The analysis was carried out on LHC data from 2010 resulting in visible peaks for all mentioned methods. Investigations of the invariant mass distributions using Monte Carlo Event Generator PYTHIA6 show a main contribution to the background by false identifications of neutral pions, that are reduced by stronger cuts on the photon pairs invariant-mass. Furthermore, the chain of afterburners that was put in place to further process the extracted peaks and compare the different reconstruction methods is demonstrated.

Beam-energy-dependent two-pion interferometry and the freeze-out eccentricity of pions measured in heavy ion collisions at the STAR detector

Science.gov (United States)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Averichev, G. S.; Banerjee, A.; Beavis, D. R.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chwastowski, J.; Codrington, M. J. M.; Contin, G.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Derradi de Souza, R.; Dhamija, S.; di Ruzza, B.; Didenko, L.; Dilks, C.; Ding, F.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Engle, K. S.; Eppley, G.; Eun, L.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Gagliardi, C. A.; Gangadharan, D. R.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Gliske, S.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Haag, B.; Hamed, A.; Han, L.-X.; Haque, R.; Harris, J. W.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huang, X.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Khan, Z. H.; Kikola, D. P.; Kisel, I.; Kisiel, A.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Kosarzewski, L. K.; Kotchenda, L.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Kycia, R. A.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; LeVine, M. J.; Li, C.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, G. L.; Ma, Y. G.; Madagodagettige Don, D. M. M. D.; Mahapatra, D. P.; Majka, R.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Minaev, N. G.; Mioduszewski, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nigmatkulov, G.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Olvitt, D. L.; Pachr, M.; Page, B. S.; Pal, S. K.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Peryt, W.; Pile, P.; Planinic, M.; Pluta, J.; Poljak, N.; Poniatowska, K.; Porter, J.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Pujahari, P. R.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Roy, A.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, B.; Shen, W. Q.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Singaraju, R. N.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Sun, X.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szelezniak, M. A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarnowsky, T.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, X. L.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y.; Xu, Z.; Yan, W.; Yang, C.; Yang, Y.; Yang, Y.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zawisza, Y.; Zbroszczyk, H.; Zha, W.; Zhang, J. B.; Zhang, J. L.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2015-07-01

We present results of analyses of two-pion interferometry in Au +Au collisions at √{sNN}=7.7 , 11.5, 19.6, 27, 39, 62.4, and 200 GeV measured in the STAR detector as part of the BNL Relativistic Heavy Ion Collider Beam Energy Scan program. The extracted correlation lengths (Hanbury-Brown-Twiss radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass (mT) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes in the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model.