Baryon Form Factors at Threshold
Baldini Ferroli, Rinaldo [Museo Storico della Fisica e Centro Studi e Ricerche ' E. Fermi' , Rome (Italy); INFN, Laboratori Nazionali di Frascati, Frascati (Italy); Pacetti, Simone [INFN and Dipartimento di Fisica, Universita di Perugia, Perugia (Italy)
2012-04-15
An extensive study of the e{sup +}e{sup -}{yields}pp{sup Macron }BABAR cross section data is presented. Two unexpected outcomes have been found: the modulus of the proton form factor is normalized to one at threshold, i.e.: |G{sup p}(4M{sub p}{sup 2})|=1, as a pointlike fermion, and the resummation factor in the Sommerfeld formula is not needed. Other e{sup +}e{sup -} {yields} baryon-antibaryon cross sections show a similar behavior near threshold.
Heavy-baryon weak form factors
It has recently been shown that hadrons containing a single heavy quark exhibit a new flavor-spin symmetry of QCD. We exploit this symmetry to obtain model-independent absolutely normalized predictions for some heavy-baryon weak form factors at zero recoil as well as relations between such form factos at nonzero recoil. (orig.)
Baryon form factors: Model-independent results
Baryon form factors can be analyzed in a largely model-independent fashion in terms of two complementary approaches. These are chiral perturbation theory and dispersion relations. I review the status of dispersive calculations of the nucleon electromagnetic form factors in the light of new data. Then, I present the leading one-loop chiral perturbation theory analysis of the hyperon and the strange nucleon form factors. Open problems and challenges are also discussed
Baryon transition form factors at the pole
Tiator, L; Workman, R L; Hadžimehmedović, M; Osmanović, H; Omerović, R; Stahov, J; Švarc, A
2016-01-01
Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the $G_M$, $G_E$, and $G_C$ form factors for the $\\Delta(1232)$ resonance excitation at the Breit-Wigner resonance and pole positions up to $Q^2=5$ GeV$^2$. We also explore the $E/M$ and $S/M$ ratios as functions of $Q^2$. For pole and residue extraction, we apply the Laurent + Pietarinen method.
Electromagnetic form factors of octet baryons in QCD
The electromagnetic form factors of octet baryons are estimated within light cone QCD sum rules method, using the most general form of the interpolating current for baryons. A comparison of our predictions on the magnetic dipole and electric form factors with the results of other approaches is performed
Heavy-to-light baryonic form factors at large recoil
Mannel, Thomas
2011-01-01
We analyze heavy-to-light baryonic form factors at large recoil and derive the scaling behavior of these form factors in the heavy quark limit. It is shown that only one universal form factor is needed to parameterize Lambda_b to p and Lambda_b to Lambda matrix elements in the large recoil limit of light baryons, while hadronic matrix elements of Lambda_b to Sigma transition vanish in the large energy limit of Sigma baryon due to the space-time parity symmetry. The scaling law of the soft form factor eta(P^{\\prime} \\cdot v), P^{\\prime} and v being the momentum of nucleon and the velocity of Lambda_b baryon, responsible for Lambda_b to p transitions is also derived using the nucleon distribution amplitudes in leading conformal spin. In particular, we verify that this scaling behavior is in full agreement with that from light-cone sum rule approach in the heavy-quark limit. With these form factors, we further investigate the Lambda baryon polarization asymmetry alpha in Lambda_b to Lambda gamma and the forward-...
Chiral analysis of baryon form factors
This work presents an extensive theoretical investigation of the structure of the nucleon within the standard model of elementary particle physics. In particular, the long range contributions to a number of various form factors parametrizing the interactions of the nucleon with an electromagnetic probe are calculated. The theoretical framework for those calculations is chiral perturbation theory, the exact low energy limit of Quantum Chromo Dynamics, which describes such long range contributions in terms of a pion-cloud. In this theory, a nonrelativistic leading one loop order calculation of the form factors parametrizing the vector transition of a nucleon to its lowest lying resonance, the Δ, a covariant calculation of the isovector and isoscalar vector form factors of the nucleon at next to leading one loop order and a covariant calculation of the isoscalar and isovector generalized vector form factors of the nucleon at leading one loop order are performed. In order to perform consistent loop calculations in the covariant formulation of chiral perturbation theory an appropriate renormalization scheme is defined in this work. All theoretical predictions are compared to phenomenology and results from lattice QCD simulations. These comparisons allow for a determination of the low energy constants of the theory. Furthermore, the possibility of chiral extrapolation, i.e. the extrapolation of lattice data from simulations at large pion masses down to the small physical pion mass is studied in detail. Statistical as well as systematic uncertainties are estimated for all results throughout this work. (orig.)
Baryon form factors from Dyson-Schwinger equations
Eichmann, Gernot
2011-01-01
I briefly summarize the application of the Dyson-Schwinger/Faddeev approach to baryon form factors. Recent results for nucleon electromagnetic and axial form factors as well as N-Delta-Gamma electromagnetic transition form factors are discussed. The calculation of the current diagrams from the quark-gluon level enables an analysis of common features, such as the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects.
Light-cone sum rule approach for Baryon form factors
Offen, Nils
2016-01-01
We present the state-of-the-art of the light-cone sum rule approach to Baryon form factors. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations.
Baryon octet electromagnetic form factors in a confining NJL model
Carrillo-Serrano, Manuel E.; Bentz, Wolfgang; Cloët, Ian C.; Thomas, Anthony W.
2016-08-01
Electromagnetic form factors of the baryon octet are studied using a Nambu-Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result that rEp quark masses.
Baryon octet electromagnetic form factors in a confining NJL model
Carrillo-Serrano, Manuel E.; Bentz, Wolfgang; Cloët, Ian C.; Thomas, Anthony W.
2016-08-01
Electromagnetic form factors of the baryon octet are studied using a Nambu-Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result that rEp based on the dressed quark masses.
Li, Hao-Song; Chen, Xiao-Lin; Deng, Wei-Zhen; Zhu, Shi-Lin
2016-01-01
We have systematically investigated the magnetic moments and magnetic form factors of the decuplet baryons to the next-to-next-leading order in the framework of the heavy baryon chiral perturbation theory. Our calculation includes the contributions from both the intermediate decuplet and octet baryon states in the loops. We also calculate the charge and magnetic dipole form factors of the decuplet baryons. Our results may be useful to the chiral extrapolation of the lattice simulations of the decuplet electromagnetic properties.
Baryon Octet Electromagnetic Form Factors in a confining NJL model
Carrillo-Serrano, Manuel E; Cloët, Ian C; Thomas, Anthony W
2016-01-01
Electromagnetic form factors of the baryon octet are studied using a Nambu--Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result $r_{E}^p < r_{E}^{\\Sigma^+}$ and $|r_{E}^n| < |r_{E}^{\\Xi^0}|$, whereas the magnetic radii have a pattern largely consistent with a naive expectation based on the dressed quark masses.
Measurement of Baryon Electromagnetic Form Factors at BESIII
Morales, Cristina Morales
2016-01-01
The Beijing $e^+e^-$-collider (BEPCII) is a double-ring symmetric collider running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range allows the BESIII-experiment to measure baryon electromagnetic form factors in direct $e^+e^-$-annihilation and in initial state radiation processes. In this paper, results on $e^+e^-\\rightarrow p\\bar{p}$ and $e^+e^-\\rightarrow \\Lambda \\bar{\\Lambda}$ based on data collected by BESIII in 2011 and 2012 are presented. Expectations from the BESIII high luminosity energy scan from 2015 and from radiative return at different center-of-mass energies are also reported.
Magnetic form factors of the octet baryons from lattice QCD and chiral extrapolation
We present a 2+1-flavor lattice QCD calculation of the electromagnetic Dirac and Pauli form factors of the octet baryons. The magnetic Sachs form factor is extrapolated at six fixed values of Q2 to physical pseudoscalar masses and infinite volume using a formulation based on heavy baryon chiral perturbation theory with finite-range regularization. We properly account for omitted disconnected quark contractions using a partially-quenched effective field theory formalism. The results compare well with the experimental form factors of the nucleon and the magnetic moments of the octet baryons.
Electric form factors of the octet baryons from lattice QCD and chiral extrapolation
We apply a formalism inspired by heavy baryon chiral perturbation theory with finite-range regularization to dynamical 2+1-flavor CSSM/QCDSF/UKQCD Collaboration lattice QCD simulation results for the electric form factors of the octet baryons. The electric form factor of each octet baryon is extrapolated to the physical pseudoscalar masses, after finite-volume corrections have been applied, at six fixed values of Q2 in the range 0.2-1.3 GeV2. The extrapolated lattice results accurately reproduce the experimental form factors of the nucleon at the physical point, indicating that omitted disconnected quark loop contributions are small. Furthermore, using the results of a recent lattice study of the magnetic form factors, we determine the ratio μpGEp/GMp. This quantity decreases with Q2 in a way qualitatively consistent with recent experimental results.
Axial form factors of the octet baryons in a covariant quark model
Ramalho, G.; Tsushima, K.
2016-07-01
We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q2. In our model the axial form factors GA(Q2) (axial-vector form factor) and GP(Q2) (induced pseudoscalar form factor) are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor gAq(Q2), and the induced pseudoscalar form factor gPq(Q2). The baryon wave functions are composed of a dominant S -state and a P -state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor gAq(Q2) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P -state mixture and the Q2 dependence of gPq(Q2), are determined by a fit to the nucleon axial form factor data obtained by lattice QCD simulations with large pion masses. In this lattice QCD regime the meson cloud effects are small, and the physics associated with the valence quarks can be better calibrated. Once the valence quark model is calibrated, we extend the model to the physical regime and use the low Q2 experimental data to estimate the meson cloud contributions for GA(Q2) and GP(Q2). Using the calibrated quark axial form factors and the generalization of the nucleon wave function for the other octet baryon members, we make predictions for all the possible weak interaction axial form factors GA(Q2) and GP(Q2) of the octet baryons. The results are compared with the corresponding experimental data for GA(0 ) and with the estimates of baryon-meson models based on S U (6 ) symmetry.
Electric form factors of the octet baryons from lattice QCD and chiral extrapolation
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M. [Adelaide Univ., SA (Australia). ARC Centre of Excellence in Particle Physics at the Terascale and CSSM; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe, Hyogo (Japan); Pleiter, D. [Forschungszentrum Juelich (Germany). JSC; Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stueben, H. [Hamburg Univ. (Germany). Regionales Rechenzentrum; Collaboration: CSSM and QCDSF/UKQCD Collaborations
2014-03-15
We apply a formalism inspired by heavy baryon chiral perturbation theory with finite-range regularization to dynamical 2+1-flavor CSSM/QCDSF/UKQCD Collaboration lattice QCD simulation results for the electric form factors of the octet baryons. The electric form factor of each octet baryon is extrapolated to the physical pseudoscalar masses, after finite-volume corrections have been applied, at six fixed values of Q{sup 2} in the range 0.2-1.3 GeV{sup 2}. The extrapolated lattice results accurately reproduce the experimental form factors of the nucleon at the physical point, indicating that omitted disconnected quark loop contributions are small. Furthermore, using the results of a recent lattice study of the magnetic form factors, we determine the ratio μ{sub p}G{sub E}{sup p}/G{sub M}{sup p}. This quantity decreases with Q{sup 2} in a way qualitatively consistent with recent experimental results.
Strange Baryon Electromagnetic Form Factors and SU(3) Flavor Symmetry Breaking
Lin, Huey-Wen; Orginos, Konstantinos
2009-01-01
We study the nucleon, Sigma and cascade octet baryon electromagnetic form factors and the effects of SU(3) flavor symmetry breaking from 2+1-flavor lattice calculations. We find that electric and magnetic radii are similar; the maximum discrepancy is about 10\\%. In the pion-mass region we explore, both the quark-component and full-baryon moments have small SU(3) symmetry breaking. We extrapolate the charge radii and the magnetic moments using three-flavor heavy-baryon chiral perturbation theory (HBXPT). The systematic errors due to chiral and continuum extrapolations remain significant, giving rise to charge radii for $p$ and $\\Sigma^-$ that are 3--4 standard deviations away from the known experimental ones. Within these systematics the predicted $\\Sigma^+$ and $\\Xi^-$ radii are 0.67(5) and 0.306(15)~fm$^2$ respectively. When the next-to-next-to-leading order of HBXPT is included, the extrapolated magnetic moments are less than 3 standard deviations away from PDG values, and the d
Initial state radiation processes can be effectively used to measure e+e− annihilation at high luminosity storage rings, such as the B–factory PEP-II in Stanford and the tau-charm factory BEPC-II in Beijing. The BaBar Collaboration has measured with unprecedented accuracy the channels e+e− → p p-bar, produced with initial state radiation at 10.6 GeV. BES-III aims to collect a luminosity of 10 fb−1 at 3.77 GeV in the next years. The measurements of the baryon electromagnetic form factors published by BaBar are summarized here together with the expectations of BES-III for the same channels.
SU(2Nf) x 0(3) light diquark symmetry and current-induced heavy baryon transition form factors
We study the current-induced bottom baryon to charm baryon transitions in the Heavy Quark Symmetry limit as mq → ∞. Our discussion involves s-wave to s-wave as well as s-wave to p-wave transitions. Using a constituent quark model picture for the light diquark system with an underlying SU(2Nf) x 0(3) symmetry and the heavy quark symmetry we arrive at a number of new predictions for the reduced form factors that describe these transitions. (author). 17 refs, 2 tabs
Extended vector meson dominance model for the baryon octet electromagnetic form factors
An unresolved issue in the present understanding of nucleon structure is the effect of hidden strangeness on electromagnetic observables such as GnE(q2). Previously, we have shown that GnE(q2) is sensitive to small φNN couplings. A complementary approach for understanding effects due to strangeness content and the Okubo-Zweig-Iizuka (OZI) rule is to investigate the electromagnetic structure of hyperons. We apply Sakurai close-quote s universality limit of the SU(3)F symmetry relations and a prescription based on the OZI rule to calculate the electromagnetic form factors of the baryon octet states (p,n,Λ,Σ+,Σ0,Σ-,Ξ0,Ξ-) within the framework of an extended vector meson dominance model. To provide additional motivation for experimental investigation, we discuss the possibility of extracting the ratio GMΛ(q2)/GMΣΛ(q2) from the Λ/Σ polarization ratio in kaon electroproduction experiments. copyright 1996 The American Physical Society
Electromagnetic baryon form factors in the Poincaré-covariant Faddeev approach
Alkofer, Reinhard, E-mail: reinhard.alkofer@uni-graz.at [Institute of Physics, University of Graz (Austria); Eichmann, Gernot; Sanchis-Alepuz, Hèlios; Williams, Richard [Institute of Theoretical Physics I, Justus-Liebig-Universität Giessen (Germany)
2015-08-15
Baryons are treated as three-quark systems using QCD degrees of freedom in Poincaré-covariant bound-state equations. The quark self-energy as well as the interaction between quarks are approximated by a vector-vector interaction via a single dressed-gluon exchange (rainbow-ladder truncation), thereby allowing a unified study of quark, meson and baryon properties. Here we will focus on the calculation of electromagnetic properties of spin-1/2 and spin-3/2 ground state baryons.
On the asymptotics of baryon form-factors in quark-gluon model
Specific asymptotic relations for the nucleon form factors are obtained in the quark-gluon model in the lowest order of the perturbation theory. Changing of signs of the nucleon form factors and strong violation of the scaling law are predicted at large momentum transfer Q2 → infinity. The relations between the γN → N and γN → Δ transition form factors are also obtained
Excited baryon form-factors at high momentum transfer at CEBAF at higher energies
Stoler, P. [Rensselaer Polytechnic Inst., Troy, NY (United States)
1994-04-01
The possibilities of measuring the properties of excited nucleons at high Q{sup 2} by means of exclusive single meson production at CEBAF with an electron energy of 8 GeV is considered. The motivation is to access short range phenomena in baryon structure, and to investigate the transition from the low Q{sup 2} non-perturbative QCD regime, where constituent quark models are valid, to higher Q{sup 2} where it is believed perturbative QCD plays an increasingly important role. It is found that high quality baryon decay angular distributions can be obtained for the most prominent states up to Q{sup 2} {approximately} 12 GeV{sup 2}/c{sup 2} using a set of moderate resolution, large solid angle magnetic spectrometers.
Study of Baryon Spectroscopy Using a New Potential Form
L. I. Abou-Salem
2014-01-01
Full Text Available In the present work, the nonrelativistic quark model is applied to study baryon systems, where the constituent quarks are bound by a suitable hyper central potential. We proposed a new phenomenological form of the interaction potential, digamma-type potential. Using the Jacobi coordinates, the three-body wave equation is solved numerically to calculate the resonance states of the N, Δ, Λ, and Σ baryon systems. The present model contains only two adjustable parameters in addition to the quark masses. Our theoretical calculations are compared to the available experimental data and Cornell potential results. The description of the spectrum shows that the ground states of the considered light and strange baryon spectra are in general well reproduced.
Forming supermassive black holes by accreting dark and baryon matter
Hu, J; Lou, Y Q; Zhang, S; Hu, Jian; Shen, Yue; Lou, Yu-Qing; Zhang, Shuangnan
2006-01-01
Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around $\\sim 10^9 M_{\\odot}$ at high redshifts $z (\\gsim 6)$. The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter onto seed black holes (BHs) created at redshifts $z\\lsim 30$ by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of $M_{\\hbox{\\tiny BH},t_1}\\backsimeq 1.4\\times 10^6\\ M_\\odot \\sigma_0/(1\\hbox{cm}^2\\hbox{g}^{-1})(C_s/30\\hbox{km s}^{-1})^4$ during $z\\sim 20-15$, where $\\sigma_0$ is the cross section per unit mass of SIDM particles and $C_s$ is the velocity dispersion in the SIDM halo referred to as an effective "sound speed". The second phase of BH mass growth is envisaged to proceed primar...
The present status of electroweak nucleon form factors and the N - Δ transition form factors is reviewed. Particularly the determination of dipole mass MA in the axial vector form factor is discussed
Scaling of Hadronic Form Factors in Point Form Kinematics
Coester, F
2003-01-01
The general features of baryon form factors calculated with point form kinematics are derived. With point form kinematics and spectator currents hadronic form factors are functions of $\\eta:={1\\over 4}(v_{out}-v_{in})^2$ and, over a range of $\\eta$ values are insensitive to unitary scale transformations of the model wave functions when the extent of the wave function is small compared to the scale defined by the constituent mass, $ \\ll 1/m^2$. The form factors are sensitive to the shape of such compact wave functions. Simple 3-quark proton wave functions are employed to illustrate these features. Rational and algebraic model wave functions lead to a reasonable representation of the empirical form factors, while Gaussian wave functions fail. For large values of $\\eta$ point form kinematics with spectator currents leads to power law behavior of the wave functions.
A brief review on the theoretical and experimental situation of baryon spectroscopy is first given. Then, the radial structure of baryons, related to the ground state form factors and the baryonic compressibility, is discussed. An experiment has been performed at Saturne laboratory (France) in which for the first time a compression of the nucleon is observed, exciting the P11 (1440 MeV) resonance (Roper resonance) by α-particles. The analysis of the data indicates that this excitation covers a large fraction of the available monopole strength in the nucleon. The derived compressibility is discussed as well as the consequence for other fields, as nuclear medium effects on baryon properties, high density phenomena in nuclear collisions as well as colour transparency. In the last point the spin-flip structure of the P11 (1440 MeV) resonance is discussed. The possibility to determine isoscalar spin-flip strength by polarized deuteron scattering is contrasted with first preliminary results from photon-induced reactions studied at Mainz which indicate a non-negligible M1 excitation of the Roper resonance. (author) 10 figs., 31 refs
Relativistic quark model for the Omega- electromagnetic form factors
G. Ramalho, K. Tsushima, Franz Gross
2009-08-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
Bloch, J. C. R.; Krassnigg, A.; Roberts, C. D.
2003-01-01
The proton's elastic electromagnetic form factors are calculated using an Ansatz for the nucleon's Poincare' covariant Faddeev amplitude that only retains scalar diquark correlations. A spectator approximation is employed for the current. On the domain of q^2 accessible in modern precision experiments these form factors are a sensitive probe of nonperturbative strong interaction dynamics. The ratio of Pauli and Dirac form factors can provide realistic constraints on models of the nucleon and ...
Hyperon elastic electromagnetic form factors in the space-like momentum region
Sanchis-Alepuz, Helios [Justus-Liebig-Universitaet Giessen, Institut fuer Theoretische Physik, Giessen (Germany); Karl-Franzens-Universitaet Graz, Institut fuer Physik, Graz (Austria); Fischer, Christian S. [Justus-Liebig-Universitaet Giessen, Institut fuer Theoretische Physik, Giessen (Germany)
2016-02-15
We present a calculation of the electric and magnetic form factors of ground-state octet and decuplet baryons including strange quarks. We work with a combination of Dyson-Schwinger equations for the quark propagator and covariant Bethe-Salpeter equations describing baryons as bound states of three (non-perturbative) quarks. Our form factors for the octet baryons are in good agreement with corresponding lattice data at finite Q{sup 2}; deviations in some isospin channels for the magnetic moments can be explained by missing meson cloud effects. At larger Q{sup 2} our quark core calculation has predictive power for both, the octet and decuplet baryons. (orig.)
Cornelis de Jager
2004-09-01
The experimental and theoretical status of elastic electron scattering from the nucleon is reviewed. As a consequence of new experimental facilities, data of unprecedented precision have recently become available for the electromagnetic and the strange form factors of the nucleon.
Electromagetic proton form factors
Hussein, M Y
2006-01-01
The electromagnetic form factors are crucial to our understanding of the proton internal structure, and thus provide a strong constraint of the distributions of the charge and magnetization current within the proton. We adopted the quark-parton model for calculating and understanding the charge structure of the proton interms of the electromagnetic form factors. A remarkable agreement with the available experimental evidence is found.
Observation of a narrow baryon resonance with positive strangeness formed in K+Xe collisions
Barmin, V. V.; Asratyan, A. E.; Borisov, V. S.; Curceanu, C.; Davidenko, G. V.; Dolgolenko, A. G.; Guaraldo, C.; Kubantsev, M. A.; Larin, I. F.; Matveev, V. A.; Shebanov, V. A.; Shishov, N. N.; Sokolov, L. I.; Tarasov, V. V.; Tumanov, G. K.; Verebryusov, V. S.; Diana Collaboration
2014-04-01
The charge-exchange reaction K+Xe→K0pXe' is investigated using the data of the DIANA experiment. The distribution of the pK0 effective mass shows a prominent enhancement near 1538 MeV formed by nearly 80 events above the background, whose width is consistent with being entirely due to the experimental resolution. Under the selections based on a simulation of K+Xe collisions, the statistical significance of the signal reaches 5.5σ. We interpret this observation as strong evidence for formation of a pentaquark baryon with positive strangeness, Θ+(uudds¯), in the charge-exchange reaction K+n→K0p on a bound neutron. The mass of the Θ+ baryon is measured as m (Θ+)=1538±2 MeV. Using the ratio between the numbers of resonant and nonresonant charge-exchange events in the peak region, the intrinsic width of this baryon resonance is determined as Γ (Θ+)=0.34±0.10 MeV.
Kees de Jager
2002-10-01
A review of data on the nucleon electro-weak form factors in the space-like region is presented. Recent results from experiments using polarized beams and either polarized targets or nucleon recoil polarimeters have yielded a significant improvement on the precision of the electromagnetic data obtained with the traditional Rosenbluth separation. An outlook is presented of planned experiments.
A Diquark-Quark Model with Its Use in Nucleon Form Factors
WANG Hong-Min; ZHANG Ben-Ai
2005-01-01
The nucleon electromagnetic form factors are investigated within a simple diquark-quark model using the light-front formalism. In this model, baryon is described as a bound state of one quark and one clustering diquark.The calculational results are compared with the experimental ones. We also regard the quarks in a baryon as pointlike constituent quarks.
Electromagnetic form factors with FLIC fermions
The fat-link irrelevant clover (FLIC) fermion action provides a new form of nonperturbative O(a) improvement and allows efficient access to the light quark-mass regime. FLIC fermions enable the construction of the nonperturbatively O(a)-improved conserved vector current without the difficulties associated with the fine tuning of the improvement coefficients. The simulations are performed with an O(a2) mean-field improved plaquette-plus-rectangle gluon action on a 203 x 40 lattice with a lattice spacing of 0.128 fm, enabling the first simulation of baryon form factors at light quark masses on a large volume lattice. Magnetic moments, electric charge radii and magnetic radii are extracted from these form factors, and show interesting chiral nonanalytic behavior in the light quark mass regime. (orig.)
Nucleon Electromagnetic Form Factors
Although nucleons account for nearly all the visible mass in the universe, they have a complicated structure that is still incompletely understood. The first indication that nucleons have an internal structure, was the measurement of the proton magnetic moment by Frisch and Stern (1933) which revealed a large deviation from the value expected for a point-like Dirac particle. The investigation of the spatial structure of the nucleon, resulting in the first quantitative measurement of the proton charge radius, was initiated by the HEPL (Stanford) experiments in the 1950s, for which Hofstadter was awarded the 1961 Nobel prize. The first indication of a non-zero neutron charge distribution was obtained by scattering thermal neutrons off atomic electrons. The recent revival of its experimental study through the operational implementation of novel instrumentation has instigated a strong theoretical interest. Nucleon electro-magnetic form factors (EMFFs) are optimally studied through the exchange of a virtual photon, in elastic electron-nucleon scattering. The momentum transferred to the nucleon by the virtual photon can be selected to probe different scales of the nucleon, from integral properties such as the charge radius to scaling properties of its internal constituents. Polarization instrumentation, polarized beams and targets, and the measurement of the polarization of the recoiling nucleon have been essential in the accurate separation of the charge and magnetic form factors and in studies of the elusive neutron charge form factor
Semileptonic heavy-to-light decays of baryons
The results about semileptonic decays of baryons with only heavy quark into light baryons are reported. These processes are considered in the framework of the quark confinement model. Weak form factors, decay rates and differential distributions of semileptonic heavy-to-light baryon decays are calculated. The limit mQ→∞ is examined. 23 refs.; 14 figs.; 1 tab
Kaplunovsky, Vadim; Melnikov, Dmitry; Sonnenschein, Jacob
2012-01-01
In the large N limit cold dense nuclear matter must be in a lattice phase. This applies also to holographic models of hadron physics. In a class of such models, like the generalized Sakai-Sugimoto model, baryons take the form of instantons of the effective flavor gauge theory that resides on probe flavor branes. In this paper we study the phase structure of baryonic crystals by analyzing discrete periodic configurations of such instantons. We find that instanton configurations exhibit a serie...
Ryong Ji, C.; Pang, A.; Szczepaniak, A. [North Carolina State Univ., Raleigh, NC (United States)
1994-04-01
It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.
Nucleon Electromagnetic Form Factors
Marc Vanderhaeghen; Charles Perdrisat; Vina Punjabi
2007-10-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at JLab, MAMI, and MIT-Bates. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.
Anomalous Sudakov Form Factors
Ciafaloni, Marcello; Comelli, Denis
2009-01-01
While radiative corrections of infrared origin normally depress high energy amplitudes (Sudakov form factors), we find that in some cases resummation of leading effects produces exponentials with positive exponents, giving rise to amplitudes that grow indefinitely with energy. The effect happens in broken gauge theories like the electroweak sector of the Standard Model, and is related to the existence of amplitudes that do not respect the gauge symmetry. Contrary to expectations, these amplitudes, although mass suppressed, do not vanish in the very high energy limit, but rather become dominant. As a working example we consider a model with two chiral abelian gauge groups U'(1)times U(1) with large mass splitting M(Z') >> M(Z), and we compute leading radiative corrections corrections to the decay of the heavy extra Z' boson into light fermions. The chirality breaking magnetic dipole moment becomes the dominant contribution to the Z' width at very high energies.
Baryon scattering at high energies. Wave function, impact factor, and gluon radiation
The scattering of a baryon consisting of three massive quarks is investigated in the high energy limit of perturbative QCD. A model of a relativistic proton-like wave function, dependent on valence quark longitudinal and transverse momenta and on quark helicities, is proposed, and we derive the baryon impact factors for two, three and four t-channel gluons. We find that the baryonic impact factor can be written as a sum of three pieces: in the first one a subsystem consisting of two of the three quarks behaves very much like the quark-antiquark pair in γ* scattering, whereas the third quark acts as a spectator. The second term belongs to the odderon, whereas in the third (C-even) piece all three quarks participate in the scattering. This term is new and has no analogue in γ* scattering. We also study the small x evolution of gluon radiation for each of these three terms. The first term follows the same pattern of gluon radiation as the γ*-initiated quark-antiquark dipole, and, in particular, it contains the BFKL evolution followed by the 2→4 transition vertex (triple Pomeron vertex). The odderon-term is described by the standard BKP evolution, and the baryon couples to both known odderon solutions, the Janik-Wosiek solution and the BLV solution. Finally, the t-channel evolution of the third term starts with a three reggeized gluon state which then, via a new 3→4 transition vertex, couples to the four gluon (two-Pomeron) state. We briefly discuss a few consequences of these findings, in particular the pattern of unitarization of high energy baryon scattering amplitudes. (orig.)
Baryon scattering at high energies. Wave function, impact factor, and gluon radiation
Bartels, J. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Motyka, L. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik]|[Jagellonian Univ., Krakow (Poland). Inst. of Physics
2007-11-15
The scattering of a baryon consisting of three massive quarks is investigated in the high energy limit of perturbative QCD. A model of a relativistic proton-like wave function, dependent on valence quark longitudinal and transverse momenta and on quark helicities, is proposed, and we derive the baryon impact factors for two, three and four t-channel gluons. We find that the baryonic impact factor can be written as a sum of three pieces: in the first one a subsystem consisting of two of the three quarks behaves very much like the quark-antiquark pair in {gamma}{sup *} scattering, whereas the third quark acts as a spectator. The second term belongs to the odderon, whereas in the third (C-even) piece all three quarks participate in the scattering. This term is new and has no analogue in {gamma}{sup *} scattering. We also study the small x evolution of gluon radiation for each of these three terms. The first term follows the same pattern of gluon radiation as the {gamma}{sup *}-initiated quark-antiquark dipole, and, in particular, it contains the BFKL evolution followed by the 2{yields}4 transition vertex (triple Pomeron vertex). The odderon-term is described by the standard BKP evolution, and the baryon couples to both known odderon solutions, the Janik-Wosiek solution and the BLV solution. Finally, the t-channel evolution of the third term starts with a three reggeized gluon state which then, via a new 3{yields}4 transition vertex, couples to the four gluon (two-Pomeron) state. We briefly discuss a few consequences of these findings, in particular the pattern of unitarization of high energy baryon scattering amplitudes. (orig.)
Excited baryon form factors at high Q2
The role of resonance electroproduction at high Q2 is discussed in the context of exclusive reactions, as well as the alternative theoretical models which are proposed to treat exclusive reactions in the few GeV2/c2 region of momentum transfer. Jefferson Lab experiment 94-014, which measured the excitation of the Delta (1232) and S11(1535) via the reactions p(e,e'p)pi0 and p(e,e'p)eta respectively at Q2 ∼ 2.8 and 4 GeV2/c2 is described, and the state of analysis reported
Measurements of Hadron Form Factors at BESIII
Morales, Cristina Morales
2016-01-01
BEPCII is a symmetric $e^+e^-$-collider located in Beijing running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range allows the BESIII-experiment to measure hadron form factors both from direct $e^+e^-$-annihilation and from initial state radiation processes. In this paper, results on $e^+e^-\\rightarrow p\\bar{p}$ based on data collected by BESIII in 2011 and 2012 are presented. We also present preliminary results on $e^+e^-\\rightarrow \\Lambda \\bar{\\Lambda}$ based on the same data samples at 4 center-of-mass energies. BESIII results obtained from $e^+e^-\\rightarrow \\pi^+\\pi^-$ using the initial state radiation technique at the center-of-mass energy of 3.773 GeV are also summarized. Finally, expectations on the measurement of baryon electromagnetic form factors from the BESIII high luminosity energy scan in 2015 and from initial state radiation processes at different center-of-mass energies are also reported.
Nucleon and Elastic and Transition Form Factors
Segovia, Jorge; Cloët, Ian C.; Roberts, Craig D.; Schmidt, Sebastian M.
2014-12-01
We present a unified study of nucleon and elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector vector contact-interaction. The comparison emphasises that experiments are sensitive to the momentum dependence of the running couplings and masses in the strong interaction sector of the Standard Model and highlights that the key to describing hadron properties is a veracious expression of dynamical chiral symmetry breaking in the bound-state problem. Amongst the results we describe, the following are of particular interest: possesses a zero at Q 2 = 9.5 GeV2; any change in the interaction which shifts a zero in the proton ratio to larger Q 2 relocates a zero in to smaller Q 2; there is likely a value of momentum transfer above which ; and the presence of strong diquark correlations within the nucleon is sufficient to understand empirical extractions of the flavour-separated form factors. Regarding the -baryon, we find that, inter alia: the electric monopole form factor exhibits a zero; the electric quadrupole form factor is negative, large in magnitude, and sensitive to the nature and strength of correlations in the Faddeev amplitude; and the magnetic octupole form factor is negative so long as rest-frame P- and D-wave correlations are included. In connection with the transition, the momentum-dependence of the magnetic transition form factor, , matches that of once the momentum transfer is high enough to pierce the meson-cloud; and the electric quadrupole ratio is a keen measure of diquark and orbital angular momentum correlations, the zero in which is obscured by meson-cloud effects on the domain currently accessible to experiment. Importantly, within each framework, identical propagators and vertices are sufficient to describe all properties discussed herein. Our
Measurement of the $\\Lambda_{b}^{0}$ Decay Form Factor
Abdallah, J; Adam, W; Adzic, P; Albrecht, T; Alderweireld, T; Alemany-Fernandez, R; Allmendinger, T; Allport, P P; Amaldi, Ugo; Amapane, N; Amato, S; Anashkin, E; Andreazza, A; Andringa, S; Anjos, N; Antilogus, P; Apel, W D; Arnoud, Y; Ask, S; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Ballestrero, A; Bambade, P; Barbier, R; Bardin, Dimitri Yuri; Barker, G; Baroncelli, A; Battaglia, Marco; Baubillier, M; Becks, K H; Begalli, M; Behrmann, A; Ben-Haim, E; Benekos, N C; Benvenuti, Alberto C; Bérat, C; Berggren, M; Berntzon, L; Bertrand, D; Besançon, M; Besson, N; Bloch, D; Blom, M; Bluj, M; Bonesini, M; Boonekamp, M; Booth, P S L; Borisov, G; Botner, O; Bouquet, B; Bowcock, T J V; Boyko, I; Bracko, M; Brenner, R; Brodet, E; Brückman, P; Brunet, J M; Bugge, L; Buschmann, P; Calvi, M; Camporesi, T; Canale, V; Carena, F; Castro, N; Cavallo, F R; Chapkin, M M; Charpentier, P; Checchia, P; Chierici, R; Shlyapnikov, P; Chudoba, J; Chung, S U; Cieslik, K; Collins, P; Contri, R; Cosme, G; Cossutti, F; Costa, M J; Crawley, B; Crennell, D J; Cuevas-Maestro, J; D'Hondt, J; Dalmau, J; Da Silva, T; Da Silva, W; Della Ricca, G; De Angelis, A; de Boer, Wim; De Clercq, C; De Lotto, B; De Maria, N; De Min, A; De Paula, L S; Di Ciaccio, Lucia; Di Simone, A; Doroba, K; Drees, J; Dris, M; Eigen, G; Ekelöf, T J C; Ellert, M; Elsing, M; Espirito-Santo, M C; Fanourakis, G K; Fassouliotis, D; Feindt, M; Fernández, J; Ferrer, A; Ferro, F; Flagmeyer, U; Föth, H; Fokitis, E; Fulda-Quenzer, F; Fuster, J A; Gandelman, M; García, C; Gavillet, P; Gazis, E N; Gokieli, R; Golob, B; Gómez-Ceballos, G; Gonçalves, P; Graziani, E; Grosdidier, G; Grzelak, K; Guy, J; Haag, C; Hallgren, A; Hamacher, K; Hamilton, K; Haug, S; Hauler, F; Hedberg, V; Hennecke, M; Herr, H; Hoffman, J; Holmgren, S O; Holt, P J; Houlden, M A; Hultqvist, K; Jackson, J N; Jarlskog, G; Jarry, P; Jeans, D; Johansson, E K; Johansson, P D; Jonsson, P; Joram, C; Jungermann, L; Kapusta, F; Katsanevas, S; Katsoufis, E C; Kernel, G; Kersevan, Borut P; Kerzel, U; Kiiskinen, A P; King, B T; Kjaer, N J; Kluit, P; Kokkinias, P; Kourkoumelis, C; Kuznetsov, O; Krumshtein, Z; Kucharczyk, M; Lamsa, J; Leder, G; Ledroit, F; Leinonen, L; Leitner, R; Lemonne, J; Lepeltier, V; Lesiak, T; Liebig, W; Liko, D; Lipniacka, A; Lopes, J H; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J; Malek, A; Maltezos, S; Mandl, F; Marco, J; Marco, R; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Masik, J; Mastroyiannopoulos, N; Matorras, F; Matteuzzi, C; Mazzucato, F; Mazzucato, M; McNulty, R; Meroni, C; Meyer, W T; Myagkov, A; Migliore, E; Mitaroff, W A; Mjörnmark, U; Moa, T; Moch, M; Mönig, K; Monge, R; Montenegro, J; Moraes, D; Moreno, S; Morettini, P; Müller, U; Münich, K; Mulders, M; Mundim, L M; Murray, W; Muryn, B; Myatt, Gerald; Myklebust, T; Nassiakou, M; Navarria, Francesco Luigi; Nawrocki, K; Nicolaidou, R; Nikolenko, M; Oblakowska-Mucha, A; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Österberg, K; Ouraou, A; Oyanguren, A; Paganoni, M; Paiano, S; Palacios, J P; Palka, H; Papadopoulou, T D; Pape, L; Parkes, C; Parodi, F; Parzefall, U; Passeri, A; Passon, O; Peralta, L; Perepelitsa, V F; Perrotta, A; Petrolini, A; Piedra, J; Pieri, L; Pierre, F; Pimenta, M; Piotto, E; Podobnik, T; Poireau, V; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Pukhaeva, N; Pullia, Antonio; Rames, J; Ramler, L; Read, A; Rebecchi, P; Rehn, J; Reid, D; Reinhardt, R; Renton, P B; Richard, F; Rídky, J; Rivero, M; Rodríguez, D; Romero, A; Ronchese, P; Rosenberg, E I; Roudeau, Patrick; Rovelli, T; Ruhlmann-Kleider, V; Ryabtchikov, D; Sadovskii, A; Salmi, L; Salt, J; Savoy-Navarro, A; Schwickerath, U; Segar, A; Sekulin, R L; Siebel, M; Sissakian, A N; Smadja, G; Smirnova, O G; Sokolov, A; Sopczak, A; Sosnowski, R; Spassoff, Tz; Stanitzki, M; Stocchi, A; Strauss, J; Stugu, B; Szczekowski, M; Szeptycka, M; Szumlak, T; Tabarelli de Fatis, T; Taffard, A C; Tegenfeldt, F; Timmermans, J; Tkatchev, L G; Tobin, M; Todorovova, S; Tomé, B; Tonazzo, A; Tortosa, P; Travnicek, P; Treille, D; Tristram, G; Trochimczuk, M; Troncon, C; Turluer, M L; Tyapkin, I A; Tyapkin, P; Tzamarias, S; Uvarov, V; Valenti, G; van Dam, P; Van Eldik, J; Van Lysebetten, A; Van Remortel, N; Van Vulpen, I B; Vegni, G; Veloso, F; Venus, W A; Verdier, P; Verzi, V; Vilanova, D; Vitale, L; Vrba, V; Wahlen, H; Washbrook, A J; Weiser, C; Wicke, D; Wickens, J H; Wilkinson, G; Winter, M; Witek, M; Yushchenko, O P; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zhuravlov, V; Zimin, N I; Zinchenko, A I; Zupan, M
2004-01-01
The form factor of Lambda_b^0 baryons is estimated using 3.46 10^6 hadronic Z decays collected by the DELPHI experiment between 1992 and 1995. Charmed Lambda_c^+ baryons fully reconstructed in the pK-pi+, pK0_S, and Lambda pi+pi+pi- modes, are associated to a lepton with opposite charge in order to select Lambda_b^0 -> Lambda_c^+ l^- anti-nu_l decays. From a combined likelihood and event rate fit to the distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be: rho-hat^2 = 2.03 +/- 0.46 (stat) ^{+0.72}_{-1.00} (syst). The exclusive semileptonic branching fraction Br(Lambda_b^0 -> Lambda_c^+ l^- anti-nu_l) can be derived from rho-hat^2 and is found to be (5.0^{+1.1}_{-0.8} (stat) ^{+1.6}_{-1.2} (syst))%. Limits on other branching fractions are also obtained.
Baryonic and Non-Baryonic Dark Matter
Carr, Bernard
2000-01-01
Cosmological nucleosynthesis calculations imply that there should be both non-baryonic and baryonic dark matter. Recent data suggest that some of the non-baryonic dark matter must be "hot" (i.e. massive neutrinos) and there may also be evidence for "cold" dark matter (i.e. WIMPs). If the baryonic dark matter resides in galactic halos, it is likely to be in the form of compact objects (i.e. MACHOs) and these would probably be the remnants of a first generation of pregalactic or protogalactic P...
Observation of a narrow baryon resonance with positive strangeness formed in $K^+$Xe collisions
Barmin, V V; Borisov, V S; Curceanu, C; Davidenko, G V; Dolgolenko, A G; Guaraldo, C; Kubantsev, M A; Larin, I F; Matveev, V A; Shebanov, V A; Shishov, N N; Sokolov, L I; Tarasov, V V; Tumanov, G K; Verebryusov, V S
2013-01-01
The data on the charge-exchange reaction K^+ Xe --> K^0 p Xe', obtained with the Xenon bubble chamber DIANA, are reanalyzed using increased statistics and modified selections. The distribution of the pK^0 effective mass shows a prominent enhancement near 1538 MeV whose width is consistent with being entirely due to experimental resolution. A corresponding enhancement at m(pK^0) \\simeq 1538 MeV and p(K^+)\\simeq 490 MeV is observed in the m(pK^0)--p(K^+) scatter plot. Using a simulation of K^+ Xe collisions that includes the development of the intranuclear cascade, we show that the observed enhancement is not a spurious structure created by the selections. The statistical significance of the signal, estimated as \\sqrt{2\\Delta\\lnL}, reaches 6.3 standard deviations. We interpret this observation as strong evidence for formation of a pentaquark baryon with positive strangeness, \\Theta^+(uudd\\bar{s}), in the charge-exchange reaction K^+ p --> K^0 n on a bound neutron. The mass of the \\Theta^+ baryon is measured as ...
Simerka - Quadratic Forms and Factorization
Lemmermeyer, Franz
2011-01-01
In this article we show that the Czech mathematician Vaclav Simerka discovered the factorization of (10^17-1)/9 using a method based on the class group of binary quadratic forms more than 120 years before Shanks and Schnorr developed similar algorithms. Simerka also gave the first examples of what later became known as Carmichael numbers.
Lomon, Earle L
2016-01-01
The pion electromagnetic form factor and two-pion production in electron-positron collisions are simultaneously fitted by a vector dominance model evolving to perturbative QCD at large momentum transfer. This model was previously successful in simultaneously fitting the nucleon electromagnetic form factors (space-like region) and the electromagnetic production of nucleon-antinucleon pairs (time-like region). For this pion case dispersion relations are used to produce the analytic connection of the space-like and time-like regions. The fit to all the data is good. The description of high-$q^2$ data, in the time-like region, requires one more meson with $\\rho$ quantum numbers than listed in the 2014 Particle Data Group review.
Nucleon electromagnetic form factors in two-flavour QCD
Capitani, S; Djukanovic, D; von Hippel, G; Hua, J; Knippschild, B Jäger B; Meyer, H B; Rae, T D; Wittig, H
2015-01-01
We present results for the nucleon electromagnetic form factors, including the momentum transfer dependence and derived quantities (charge radii and magnetic moment). The analysis is performed using O(a) improved Wilson fermions in Nf=2 QCD measured on the CLS ensembles. Particular focus is placed on a systematic evaluation of the influence of excited states in three-point correlation functions, which lead to a biased evaluation, if not accounted for correctly. We argue that the use of summed operator insertions and fit ans\\"atze including excited states allow us to suppress and control this effect. We employ a novel method to perform joint chiral and continuum extrapolations, by fitting the form factors directly to the expressions of covariant baryonic chiral effective field theory. The final results for the charge radii and magnetic moment from our lattice calculations include, for the first time, a full error budget. We find that our estimates are compatible with experimental results within their overall u...
SU(3) breaking in hyperon transition vector form factors
We present a calculation of the SU(3)-breaking corrections to the hyperon transition vector form factors to O(p4) in heavy baryon chiral perturbation theory with finite-range regularisation. Both octet and decuplet degrees of freedom are included. We formulate a chiral expansion at the kinematic point Q2=-(MB1-MB2)2, which can be conveniently accessed in lattice QCD. The two unknown low-energy constants at this point are constrained by lattice QCD simulation results for the Σ-→n and Ξ0→Σ+ transition form factors. Hence we determine lattice-informed values of f1 at the physical point. This work constitutes progress towards the precise determination of vertical stroke Vus vertical stroke from hyperon semileptonic decays.
SU(3) breaking in hyperon transition vector form factors
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M. [ARC Centre of Excellence in Particle Physics at the Terascale, Adelaide (Australia); Centre for the Subatomic Structure of Matter (CSSM), Adelaide, SA (Australia); Adelaide Univ., SA (Australia). Dept. of Physics; Cooke, A.N.; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe (Japan); Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Division; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2015-08-15
We present a calculation of the SU(3)-breaking corrections to the hyperon transition vector form factors to O(p{sup 4}) in heavy baryon chiral perturbation theory with finite-range regularisation. Both octet and decuplet degrees of freedom are included. We formulate a chiral expansion at the kinematic point Q{sup 2}=-(M{sub B{sub 1}}-M{sub B{sub 2}}){sup 2}, which can be conveniently accessed in lattice QCD. The two unknown low-energy constants at this point are constrained by lattice QCD simulation results for the Σ{sup -}→n and Ξ{sup 0}→Σ{sup +} transition form factors. Hence we determine lattice-informed values of f{sub 1} at the physical point. This work constitutes progress towards the precise determination of vertical stroke V{sub us} vertical stroke from hyperon semileptonic decays.
Factorization and pion form factor in QCD
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 Q2 momentum behaviour of the pion EMFF in QCD. Pion EMFF asymptotics is expressed in terms of fu fundamental constants of the theory
This paper contains a discussion of the spectrum of the lowest-lying charm baryons and review the experimental status of the masses of charm baryons and briefly comment on theoretical attempts to understand their spectroscopy. Lifetime measurements and lifetime hierarchies suggested by the interplay of various theoretical mechanisms contributing to the decay and semileptonic decays of charm baryons are discussed. It also treats exclusive nonleptonic charm baryon decays, where there are more data to be compared to theoretical modeling, and contains a summary and an outlook on future charm baryon experiments
Kaplunovsky, Vadim; Sonnenschein, Jacob
2012-01-01
In the large N limit cold dense nuclear matter must be in a lattice phase. This applies also to holographic models of hadron physics. In a class of such models, like the generalized Sakai-Sugimoto model, baryons take the form of instantons of the effective flavor gauge theory that resides on probe flavor branes. In this paper we study the phase structure of baryonic crystals by analyzing discrete periodic configurations of such instantons. We find that instanton configurations exhibit a series of "popcorn" transitions upon increasing the density. Through these transitions normal (3D) lattices expand into the transverse dimension, eventually becoming a higher dimensional (4D) multi-layer lattice at large densities. We consider 3D lattices of zero size instantons as well as 1D periodic chains of finite size instantons, which serve as toy models of the full holographic systems. In particular, for the finite-size case we determine solutions of the corresponding ADHM equations for both a straight chain and for a 2...
We review the experimental and theoretical status of baryons containing one heavy quark. The charm and bottom baryon states are classified and their mass spectra are listed. The appropriate theoretical framework for the description of heavy baryons is the Heavy Quark Effective Theory, whose general ideas and methods are introduced and illustrated in specific examples. We present simple covariant expressions for the spin wave functions of heavy baryons including p-wave baryons. The covariant spin wave functions are used to determine the Heavy Quark Symmetry structure of flavour-changing current-induced transitions between heavy baryons as well as one-pion and one-photon transitions between heavy baryons of the same flavour. We discuss 1/mQ corrections to the current-induced transitions as well as the structure of heavy to light baryon transitions. Whenever possible we attempt to present numbers to compare with experiment by making use of further model-dependent assumptions as e.g. the constituent picture for light quarks. We highlight recent advances in the theoretical understanding of the inclusive decays of hadrons containing one heavy quark including polarization. For exclusive semileptonic decays we discuss rates, angular decay distributions and polarization effects. We provide an update of the experimental and theoretical status of lifetimes of heavy baryons and of exclusive nonleptonic two body decays of charm baryons. (orig.)
Nakamura, Gen; Huetsi, Gert; Sato, Takahiro; Yamamoto, Kazuhiro
2009-01-01
We determine a constraint on the growth factor by measuring the damping of the baryon acoustic oscillations in the matter power spectrum using the Sloan Digital Sky Survey luminous red galaxy sample. The damping of the BAO is detected at the one sigma level. We obtain \\sigma_8D_1(z=0.3) = 0.42^{+0.34}_{-0.28} at the 1\\sigma statistical level, where \\sigma_8 is the root mean square overdensity in a sphere of radius 8h^{-1}Mpc and D_1(z) is the growth factor at redshift z. The above result assu...
Delta and Omega electromagnetic form factors in a Dyson-Schwinger/Bethe-Salpeter approach
Diana Nicmorus, Gernot Eichmann, Reinhard Alkofer
2010-12-01
We investigate the electromagnetic form factors of the Delta and the Omega baryons within the Poincare-covariant framework of Dyson-Schwinger and Bethe-Salpeter equations. The three-quark core contributions of the form factors are evaluated by employing a quark-diquark approximation. We use a consistent setup for the quark-gluon dressing, the quark-quark bound-state kernel and the quark-photon interaction. Our predictions for the multipole form factors are compatible with available experimental data and quark-model estimates. The current-quark mass evolution of the static electromagnetic properties agrees with results provided by lattice calculations.
Kaplunovsky, Vadim; Melnikov, Dmitry; Sonnenschein, Jacob
2012-11-01
In the large N c limit cold dense nuclear matter must be in a lattice phase. This applies also to holographic models of hadron physics. In a class of such models, like the generalized Sakai-Sugimoto model, baryons take the form of instantons of the effective flavor gauge theory that resides on probe flavor branes. In this paper we study the phase structure of baryonic crystals by analyzing discrete periodic configurations of such instantons. We find that instanton configurations exhibit a series of "popcorn" transitions upon increasing the density. Through these transitions normal (3D) lattices expand into the transverse dimension, eventually becoming a higher dimensional (4D) multi-layer lattice at large densities. We consider 3D lattices of zero size instantons as well as 1D periodic chains of finite size instantons, which serve as toy models of the full holographic systems. In particular, for the finite-size case we determine solutions of the corresponding ADHM equations for both a straight chain and for a 2D zigzag configuration where instantons pop up into the holographic dimension. At low density the system takes the form of an "abelian anti- ferromagnetic" straight periodic chain. Above a critical density there is a second order phase transition into a zigzag structure. An even higher density yields a rich phase space characterized by the formation of multi-layer zigzag structures. The finite size of the lattices in the transverse dimension is a signal of an emerging Fermi sea of quarks. We thus propose that the popcorn transitions indicate the onset of the "quarkyonic" phase of the cold dense nuclear matter.
First lattice calculation of charmed hadrons' electromagnetic form factors
Electromagnetic form factors of D and D* mesons and Ξcc, Σc, Ωc and Ωcc baryons are calculated in 2+1 flavor lattice QCD. As a by product of this calculation electric/magnetic charge radii and magnetic moments are extracted. Compared to the PDG values of the light- sector, i.e. pion and proton, charmed hadron results are systematically smaller
Effects of the d-state quarks on the nucleon electric form factors
Considering the d-orbital excitation of a quark in the bag, we calculate the nucleon electric form factors in the cloudy bag model. In these calculations, we have taken into account the πNN, πΔN and πγ form factors though neglecting the c.m. correction. It turns out that the neutron charge form factor is very sensitive to the d-state quark admixture in the overall region of the momentum transfer but the proton charge form factor remains unchanged. Taking the d-state quark admixture in the intermediate state baryons, we can obtain the nucleon rms radii in remarkable agreement with the experimental values. We also investigate the roles of Δ particles in the nucleon charge form factors. (author). 20 refs, 10 figs
Radiative decays of negative parity heavy baryons in QCD
Agamaliev, A K; Savcı, M
2016-01-01
The transition form factors responsible for the radiative $\\Sigma_Q \\to \\Lambda_Q \\gamma$ and $\\Xi_Q^\\prime \\to \\Xi \\gamma$ decays of the negative parity baryons are examined within light cone QCD sum rules. The decay widths of the radiative transitions are calculated using the obtained results of the form factors.
On form factors of boundary changing operators
Bajnok, Zoltan
2015-01-01
We develop a form factor bootstrap program to determine the matrix elements of local, boundary condition changing operators. We propose axioms for these form factors and determine their solutions in the free boson and Lee-Yang models. The sudden change in the boundary condition, caused by an operator insertion, can be interpreted as a local quench and the form factors provide the overlap of any state before the quench with any outgoing state after the quench.
On form factors of boundary changing operators
Z. Bajnok
2016-04-01
Full Text Available We develop a form factor bootstrap program to determine the matrix elements of local, boundary condition changing operators. We propose axioms for these form factors and determine their solutions in the free boson and Lee–Yang models. The sudden change in the boundary condition, caused by an operator insertion, can be interpreted as a local quench and the form factors provide the overlap of any state before the quench with any outgoing state after the quench.
Soliton form factors from lattice simulations
Rajantie, Arttu
2010-01-01
The form factor provides a convenient way to describe properties of topological solitons in the full quantum theory, when semiclassical concepts are not applicable. It is demonstrated that the form factor can be calculated numerically using lattice Monte Carlo simulations. The approach is very general and can be applied to essentially any type of soliton. The technique is illustrated by calculating the kink form factor near the critical point in 1+1-dimensional scalar field theory. As expected from universality arguments, the result agrees with the exactly calculable scaling form factor of the two-dimensional Ising model.
Lambda_b -> Lambda l+ l- form factors and differential branching fraction from lattice QCD
Detmold, William; Lin, C. -J. David; Meinel, Stefan; Wingate, Matthew
2012-01-01
We present the first lattice QCD determination of the $\\Lambda_b \\to \\Lambda$ transition form factors that govern the rare baryonic decays $\\Lambda_b \\to \\Lambda l^+ l^-$ at leading order in heavy-quark effective theory. Our calculations are performed with 2+1 flavors of domain-wall fermions, at two lattice spacings and with pion masses down to 227 MeV. Three-point functions with a wide range of source-sink separations are used to extract the ground-state contributions. The form factors are e...
Dark matter, first definitely found in the large clusters of galaxies, is now known to be dominant mass in the outer parts of galaxies. All the mass definitely deduced could be made up of baryons, and this would fit well with the requirements of nucleosynthesis in a big bang of small ΩB. However, if inflation is the explanation of the expansion and large scale homogeneity of the universe and of baryon synthesis, and if the universe did not have an infinite extent at the big bang, then Ω should be minutely greater than unity. It is commonly hypothesized that most mass is composed of some unknown, non-baryonic form. This book first discusses the known forms, comets, planets, brown dwarfs, stars, gas, galaxies and Lyman α clouds in which baryons are known to exist. Limits on the amount of dark matter in baryonic form are discussed in the context of the big bang. Inhomogeneities of the right type alleviate the difficulties associated with ΩB = 1 cosmological nucleosynthesis
Nucleon and Δ Elastic and Transition Form Factors
We present a unified study of nucleon and Δ elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector ⊗ vector contact-interaction. The comparison emphasises that experiments are sensitive to the momentum dependence of the running couplings and masses in the strong interaction sector of the Standard Model and highlights that the key to describing hadron properties is a veracious expression of dynamical chiral symmetry breaking in the bound-state problem. Amongst the results we describe, the following are of particular interest: GpE(Q2)/GpM(Q2) possesses a zero at Q2 = 9.5 GeV2; any change in the interaction which shifts a zero in the proton ratio to larger Q2 relocates a zero in GnE(Q2)/GnM(Q2) to smaller Q2; there is likely a value of momentum transfer above which GnE>GpE ; and the presence of strong diquark correlations within the nucleon is sufficient to understand empirical extractions of the flavour-separated form factors. Regarding the Δ(1232) -baryon, we find that, inter alia: the electric monopole form factor exhibits a zero; the electric quadrupole form factor is negative, large in magnitude, and sensitive to the nature and strength of correlations in the Δ(1232) Faddeev amplitude; and the magnetic octupole form factor is negative so long as rest-frame P- and D-wave correlations are included. In connection with the N→Δ transition, the momentum-dependence of the magnetic transition form factor, G∗M , matches that of GnM once the momentum transfer is high enough to pierce the meson-cloud; and the electric quadrupole ratio is a keen measure of diquark and orbital angular momentum correlations, the zero in which is obscured by meson-cloud effects on the domain currently accessible to experiment. Importantly, within each framework, identical propagators
Light-cone sum rules for the nucleon form factors in NLO
In this work the leading-twist next-to-leading order (NLO) correction to the light-cone sum rules prediction for the electromagnetic form factors of the nucleon are calculated. Here the Ioffe nucleon interpolation current is used and it is worked in the MN=0 approximation, with MN being the mass of the nucleon. In this approximation, only the Pauli form factor F2 receives a correction and the calculated correction is quite sizable. The numerical results for the proton form factors show the improved agreement with the experimental data. Furthermore the problems encountered when going away from MN=0 approximation at NLO, as well as, gauge invariance of the perturbative results are discussed. This work presents the first step towards the NLO accuracy in the light-cone sum rules for baryon form factors. (orig.)
Price, Sedona H.; Kriek, Mariska; Shapley, Alice E.; Reddy, Naveen A.; Freeman, William R.; Coil, Alison L.; de Groot, Laura; Shivaei, Irene; Siana, Brian; Azadi, Mojegan; Barro, Guillermo; Mobasher, Bahram; Sanders, Ryan L.; Zick, Tom
2016-03-01
We present {{H}}α gas kinematics for 178 star-forming galaxies at z˜ 2 from the MOSFIRE Deep Evolution Field survey. We have developed models to interpret the kinematic measurements from fixed-angle multi-object spectroscopy, using structural parameters derived from Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey Hubble Space Telescope/F160W imaging. For 35 galaxies, we measure resolved rotation with a median of {(V/{σ }V,0)}{RE} = 2.1. We derive dynamical masses from the kinematics and sizes and compare them to baryonic masses, with gas masses estimated from dust-corrected {{H}}α star formation rates (SFRs) and the Kennicutt-Schmidt relation. When assuming that galaxies with and without observed rotation have the same median {(V/{σ }V,0)}{RE}, we find good agreement between the dynamical and baryonic masses, with a scatter of {σ }{rms} = 0.34 {dex} and a median offset of {{Δ }}{{log}}10 M = 0.04 {dex}. This comparison implies a low dark matter fraction (8% within an effective radius) for a Chabrier initial mass function (IMF), and disfavors a Salpeter IMF. Moreover, the requirement that {M}{dyn}/{M}{baryon} should be independent of inclination yields a median value of {(V/{σ }V,0)}{RE} = 2.1 for galaxies without observed rotation. If, instead, we treat the galaxies without detected rotation as early-type galaxies, the masses are also in reasonable agreement ({{Δ }}{{log}}10 M = -0.07 {dex}, {σ }{rms} = 0.37 {dex}). The inclusion of gas masses is critical in this comparison; if gas masses are excluded, there is an increasing trend of {M}{dyn}/{M}* with higher specific SFR (SSFR). Furthermore, we find indications that V/σ decreases with increasing {{H}}α SSFR for our full sample, which may reflect disk settling. We also study the Tully-Fisher relation and find that at fixed stellar mass {S}0.5 = {(0.5{V}2.22+{σ }V,02)}1/2 was higher at earlier times. At fixed baryonic mass, we observe the opposite trend. Finally, the baryonic and
Electromagnetic form factors of the nucleon
Schmieden, H.
2003-01-01
Elastic form factors provide information about the low energy structure of composite particles.Recent double polarization coincidence experiments significantly improved our knowledge of proton and neutron form factors. Recoil polarization measurements in the p(\\vec e, e' \\vec p) reaction proved that at momentum transfers above Q^2 \\simeq 1.5 (GeV/c)^2 the electric form factor of the proton falls significantly faster than the dipole expectation. The close--to--dipole shape at low Q^2 of the ne...
Form Factor and Boundary Contribution of Amplitude
Huang, Rijun; Feng, Bo
2016-01-01
The boundary contribution of an amplitude in the BCFW recursion relation can be considered as a form factor involving boundary operator and unshifted particles. At the tree-level, we show that by suitable construction of Lagrangian, one can relate the leading order term of boundary operators to some composite operators of N=4 super-Yang-Mills theory, then the computation of form factors is translated to the computation of amplitudes. We compute the form factors of these composite operators through the computation of corresponding double trace amplitudes.
Pseudoscalar meson form factors and decays
Dorokhov, A E
2011-01-01
In this communication we discuss few topics related with modern experimental data on the physics of light pseudoscalar mesons. It includes the contribution of the pseudoscalar mesons to the muon anomalous magnetic moment (AMM), $g-2$, the rare decays of light pseudoscalar mesons to lepton pair, the transition form factors of pseudoscalar mesons at large momentum transfer, the pion transversity form factor. Measuring the muon anomalous magnetic moment $g-2$ and the rare decays of light pseudoscalar mesons into lepton pair $P\\rightarrow l^{+}l^{-} $ serve as important test of the standard model. To reduce the theoretical uncertainty in the standard model predictions the data on the transition form factors of light pseudoscalar mesons play significant role. Recently new data on behavior of these form factors at large momentum transfer was supplied by the BABAR collaboration. Within the nonlocal chiral quark model it shown how to describe these data and how the meson distribution amplitude evolves as a function o...
Aleksan, R.; Yaouanc, A. Le; Oliver, L.; Pène, O; Raynal, J. -C.
1994-01-01
The heavy to light form factors in $B$ decays are discussed. Critical discussion of theoretical approaches is made with special emphasis on their failure to describe the $B \\to K^{(\\ast )}\\psi$ data.
Make Projects Small Form Factor PCs
Wessels, Duane
2006-01-01
Shoebox sized and smaller, small-form-factor PCs can pack as much computing muscle as a full-sized desktop computer. They consumer less power, have few or no moving parts, and are very quiet. Whether you plan to use one as a standalone PC or want to embed it in your next hacking project, a small-form-factor PC can be a lot of fun to build. Make Projects: Small Form Factor PCs is the only book available that shows you how to build small-form-factor PCs -- from kits and from scratch -- that are more interesting and more personalized than what a full-sized PC can give you. Included in the book
Separation energy dependence of hole form factors
Form factors of fragmented hole states are studied within the quasiparticle-phonon model, using the inhomogeneous equation method. The validity of this method is successfully checked by comparison with coupled equation solutions in schematic vibrational model cases. A systematic investigation of form factors is performed for neutron and proton hole states in the valence and first inner shells of 208Pb. Large fluctuations of form factor radii are observed for individual levels superimposed on a general increase with separation energy. Average characteristics are introduced for groups of levels, namely the mean form factors, summed source terms and correction potentials, and their behaviour is presented. The role of the relative values of the interaction radius parameter and binding well radius is discussed in detail. (orig.)
Problems in baryon spectroscopy
Capstick, S. [Florida State Univ., Tallahassee, FL (United States)
1994-04-01
Current issues and problems in the physics of ground- and excited-state baryons are considered, and are classified into those which should be resolved by CEBAF in its present form, and those which may require CEBAF to undergo an energy upgrade to 8 GeV or more. Recent theoretical developments designed to address these problems are outlined.
Paolis, F.; Ingrosso, G.; Jetzer, Ph.; Roncadelli, M.
1997-01-01
Reasons supporting the idea that most of the dark matter in galaxies and clusters of galaxies is baryonic are discussed. Moreover, it is argued that most of the dark matter in galactic halos should be in the form of MACHOs and cold molecular clouds.
Spectral Content of Isoscalar Nucleon Form Factors
Hammer, H. -W.; Ramsey-Musolf, M. J.
1998-01-01
The nucleon strange vector and isoscalar electromagnetic form factors are studied using a spectral decomposition. The K\\bar{K} contribution to the electric and magnetic radii as well as the magnetic moment is evaluated to all orders in the strong interaction using an analytic continuation of experimental KN scattering amplitudes and bounds from unitarity. The relationship between non-resonant and resonant K\\bar{K} contributions to the form factors is demonstrated, and values for the vector an...
Electromagnetic structure of octet baryons
A numerical simulation of quenched QCD on a 24x12x12x24 lattice at β=5.9 is used to calculate the electric and magnetic form factors of the baryon octet. General forms of the baryon interpolating fields are considered. Magnetic moments, electric radii, magnetic radii, and magnetic transition moments are extracted from the form factors. The electric properties are found to be consistent with a quark-model picture involving spin-dependent forces. The lattice results for the magnetic properties show a mass and spin dependence of the effective quark moments which is not accounted for in conventional quark models. Lattice calculations underestimate the magnitude of electric radii, magnetic radii, and magnetic moments compared to experimental measurements. The finite volume of the periodic lattice may be responsible for the discrepancies. The pattern of electromagnetic radii in the lattice results are seen to be generally reproduced in the model results that are considered. The only exception is that of Ξ- which proves to be a sensitive probe of the quark dynamics. Lattice calculations indicate a positive value for the normalized square magnetic radius in Ξ- which contrasts Skyrme model results. Ratios of the magnetic moments allow a more detailed comparison with the experimental measurements. The lattice calculations are seen to better reproduce the experimental ratios than the model calculations
Electromagnetic and axial structures of Baryon ground and resonant states
This thesis is devoted to the investigation of the electroweak structures of baryons. One performs a comprehensive study of the electromagnetic and axial form factors of baryon ground states with flavors 'up', 'down', and 'strange'; regarding baryon resonances the axial charges are investigated. The dynamics for the description of baryons is furnished by the relativistic constituent-quark model, of which three different variants are applied here. The calculations are performed in the framework of relativistic quantum mechanics, where the electromagnetic and axial current operators are constructed along a spectator model in the point-form.While the evaluations of the electroweak form factors are based on an already established formalism, one develops a generally valid formulation for the axial charges. Thereby it becomes possible to calculate these quantities for arbitrary baryon states and completely general interaction models.It turns out that relativistic constituent-quark models can describe in the framework of a Poincare-invariant formalism not only the electromagnetic but also the axial form factors, which are calculated here for the first time for all baryons. Globally, a good agreement with experiment is achieved up to momentum transfers of about 4 GeV/c. With regard to the particularly sensitive quantities, like the electric radii and magnetic moments, the constituent-quark model based on Goldstone-boson exchange yields the best results. In cases, where no experimental data exist, the predictions agree well with results from lattice quantum chromodynamics. The analogue is true for the axial charges of baryon ground and resonant states. Except for some special cases, their values are presented here for the first time comprehensively and consistently. (author)
Hadronic Form Factors and Perturbative QCD
Sterman, George F; Sterman, George; Stoler, Paul
1997-01-01
The electromagnetic form factors of hadrons at large momentum transfer have been the subject of intense theoretical and experimental scrutiny over the past two decades, yet there is still not a universally-accepted framework for their description. This review is a synopsis of their current status at large momentum transfer. The basic theoretical approaches to form factors at large momentum transfer are developed, emphasizing the valence quark and Feynman (soft) pictures. The discussion includes the relation of these descriptions to the parton model, as well as the roles of factorization, evolution, Sudakov resummation and QCD sum rules. This is followed by a discussion of the experimental status of pion and nucleon elastic form factors and resonance production amplitudes in the light of recent data, highlighting the successes and shortcomings of various theoretical proposals.
Nucleon form factors and hidden symmetry in holographic QCD
The vector dominance of the electromagnetic (EM) form factors both for mesons and baryons arises naturally in holographic QCD, where both the number of colors and the 't Hooft coupling are taken to be very large, offering a bona-fide derivation of the notion of vector dominance. The crucial ingredient for this is the infinite tower of vector mesons in the approximations made which share features that are characteristic of the quenched approximation in lattice QCD. We approximate the infinite sum by contributions from the lowest four vector mesons of the tower which turn out to saturate the charge and magnetic moment sum rules within a few % and compute them totally free of unknown parameters for momentum transfers Q2 approx.= 1 GeV2. We identify certain observables that can be reliably computed within the approximations and others that are not, and discuss how the improvement of the latter can enable one to bring holographic QCD closer to QCD proper. (author)
Paramagnetic form factors from itinerant electron theory
Elastic neutron scattering experiments performed over the past two decades have provided accurate information about the magnetic form factors of paramagnetic transition metals. These measurements have traditionally been analyzed in terms of an atomic-like theory. There are, however, some cases where this procedure does not work, and there remains the overall conceptual problem of using an atomistic theory for systems where the unpaired-spin electrons are itinerant. We have recently developed computer codes for efficiently evaluating the induced magnetic form factors of fcc and bcc itinerant electron paramagnets. Results for the orbital and spin contributions have been obtained for Cr, Nb, V, Mo, Pd and Rh based on local density bands. By using calculated spin enhancement parameters, we find reasonable agreement between theory and neutron form factor data. In addition, these zero parameter calculations yield predictions for the bulk susceptibility on an absolute scale which are in reasonable agreement with experiment in all treated cases except palladium
Form factors for semileptonic D decays
Palmer, Teresa
2013-01-01
We study the form factors for semileptonic decays of $D$-mesons. That is, we consider the matrix element of the weak left-handed quark current for the transitions $D \\rightarrow P$ and $D \\rightarrow V$, where $P$ and $V$ are light pseudoscalar or vector mesons, respectively. Our motivation to perform the present study of these form factors are future calculations of non-leptonic decay amplitudes. We consider the form factors within a class of chiral quark models. Especially, we study how the Large Energy Effective Theory (LEET) limit works for $D$-meson decays. Compared to previous work we also introduce light vector mesons $V = \\rho, K^*,...$ within chiral quark models. In order to determine some of the parameters in our model, we use existing data and results based on some other methods like lattice calculations, light-cone sum rules, and heavy-light chiral perturbation theory. We also obtain some predictions within our framework.
The Form Factors of the Nucleons
Perdrisat, Charles F. [William and Mary College, JLAB
2013-11-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double-polarization experiments, in comparison with with pre-vious unpolarized cross section data. Here we will review the experimental data base in view of the new results for the proton and the neutron, obtained at MIT-Bates, JLab and MAMI. The rapid evolution of phenomenological models triggered by these high- precision experiments will be discussed. In particular, the possibility that the proton is non-spherical in its ground state, and that the transverse charge density are model in- dependently defined in the infinite momentum frame. Likewise, flavor decomposition of the nucleon form factors into dressed u and d quark form factors, may give information about the quark-diquark structure of the nucleon. The current proton radius "crisis" will also be discussed.
Nucleon Form Factors - A Jefferson Lab Perspective
Arrington, John; Perdrisat, Charles F
2011-01-01
The charge and magnetization distributions of the proton and neutron are encoded in their elastic electromagnetic form factors, which can be measured in elastic electron--nucleon scattering. By measuring the form factors, we probe the spatial distribution of the proton charge and magnetization, providing the most direct connection to the spatial distribution of quarks inside the proton. For decades, the form factors were probed through measurements of unpolarized elastic electron scattering, but by the 1980s, progress slowed dramatically due to the intrinsic limitations of the unpolarized measurements. Early measurements at several laboratories demonstrated the feasibility and power of measurements using polarization degrees of freedom to probe the spatial structure of the nucleon. A program of polarization measurements at Jefferson Lab led to a renaissance in the field of study, and significant new insight into the structure of matter.
Hadronic form factors in kaon photoproduction
Syukurilla, L., E-mail: tmart@fisika.ui.ac.id; Mart, T., E-mail: tmart@fisika.ui.ac.id [Department Fisika, FMIPA, Universitas Indonesia, Depok, 164242 (Indonesia)
2014-09-25
We have revisited the effect of hadronic form factors in kaon photoproduction process by utilizing an isobaric model developed for kaon photoproduction off the proton. The model is able to reproduce the available experimental data nicely as well as to reveal the origin of the second peak in the total cross section, which was the main source of confusion for decades. Different from our previous study, in the present work we explore the possibility of using different hadronic form factors in each of the KΛN vertices. The use of different hadronic form factors, e.g. dipole, Gaussian, and generalized dipole, has been found to produce a more flexible isobar model, which can provide a significant improvement in the model.
Nucleon Form Factors - A Jefferson Lab Perspective
John Arrington, Kees de Jager, Charles F. Perdrisat
2011-06-01
The charge and magnetization distributions of the proton and neutron are encoded in their elastic electromagnetic form factors, which can be measured in elastic electron--nucleon scattering. By measuring the form factors, we probe the spatial distribution of the proton charge and magnetization, providing the most direct connection to the spatial distribution of quarks inside the proton. For decades, the form factors were probed through measurements of unpolarized elastic electron scattering, but by the 1980s, progress slowed dramatically due to the intrinsic limitations of the unpolarized measurements. Early measurements at several laboratories demonstrated the feasibility and power of measurements using polarization degrees of freedom to probe the spatial structure of the nucleon. A program of polarization measurements at Jefferson Lab led to a renaissance in the field of study, and significant new insight into the structure of matter.
Color-kinematic duality for form factors
Boels, Rutger H.; Kniehl, Bernd A.; Tarasov, Oleg V.; Yang, Gang [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2012-12-15
Recently a powerful duality between color and kinematics has been proposed for integrands of scattering amplitudes in quite general gauge theories. In this paper the duality proposal is extended to the more general class of gauge theory observables formed by form factors. After a discussion of the general setup the existence of the duality is verified in two and three loop examples in four dimensional maximally supersymmetric Yang-Mills theory which involve the stress energy tensor multiplet. In these cases the duality reproduces known results in a particularly transparent and uniform way. As a non-trivial application we obtain a very simple form of the integrand of the four-loop two-point (Sudakov) form factor which passes a large set of unitarity cut checks.
Color-kinematic duality for form factors
Recently a powerful duality between color and kinematics has been proposed for integrands of scattering amplitudes in quite general gauge theories. In this paper the duality proposal is extended to the more general class of gauge theory observables formed by form factors. After a discussion of the general setup the existence of the duality is verified in two and three loop examples in four dimensional maximally supersymmetric Yang-Mills theory which involve the stress energy tensor multiplet. In these cases the duality reproduces known results in a particularly transparent and uniform way. As a non-trivial application we obtain a very simple form of the integrand of the four-loop two-point (Sudakov) form factor which passes a large set of unitarity cut checks.
The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested
Aerodynamic Performance of Low Form Factor Spoilers
Harley, Christopher Donald
2011-01-01
The development of low form factor flight controls is driven by the benefits of reducingthe installed volume of the control device and/or minimising the change in external geometry, with particular application to flight control of low observable aircraft. Forthis work, the term „low form factor‟ does not refer to the aspect ratio of the controldevice rather the overall installed volume. This thesis compares the use of low formfactor geometric and f...
Form Factors of Kaon Semileptonic Decays
Afanasiev, A M; Afanasev, Andrei
1996-01-01
A calculation of the semi--leptonic decays of the kaon ($K_{l3}$) is presented. The results are direct predictions of a covariant model of the pion and kaon introduced earlier by Ito, Buck, Gross. The weak form factors for $K_{l3}$ are predicted with absolutely no parameter adjustments of the model. We obtained for the form factor parameters: $f_-(q^2=m_l^2)/f_+(q^2=m_l^2)=-0.28$ and $\\lambda_+$= 0.028, both within experimental error bars. Connections of this approach to heavy quark symmetry will also be discussed.
Nucleon electromagnetic form factors with Wilson fermions
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Nucleon electromagnetic form factors with Wilson fermions
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2007-10-15
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
From form factors to generalized parton distributions
Diehl, Markus
2013-06-15
I present an extraction of generalized parton distributions from selected data on the electromagnetic nucleon form factors. The extracted distributions can in particular be used to quantify the contribution to the proton spin from the total angular momentum carried by valence quarks, as well as their transverse spatial distribution inside the proton.
From form factors to generalized parton distributions
I present an extraction of generalized parton distributions from selected data on the electromagnetic nucleon form factors. The extracted distributions can in particular be used to quantify the contribution to the proton spin from the total angular momentum carried by valence quarks, as well as their transverse spatial distribution inside the proton.
Form factors from unitarity and analyticity
The report demonstrates how the calculation of form factors is performed within the S-matrix framework. Two examples are considered. A simple model of composite particles is studied in order to reveal the connection between the binding energy of the particle and its structure. A particular contribution to the magnetic moment of the nucleon is constructed from mass shell triodes
Burkert, A; Bouche, N; Cresci, G; Khochfar, S; Sommer-Larsen, J; Sternberg, A; Naab, T; Foerster-Schreiber, N; Tacconi, L; Shapiro, K; Hicks, E; Lutz, D; Davies, R; Buschkamp, P; Genel, S
2009-01-01
The structure of a sample of high-redshift (z=2), rotating galaxies with high star formation rates and turbulent gas velocities of sigma=40-80 km/s is investigated. Fitting the observed disk rotational velocities and radii with a Mo, Mao, White (1998) (MMW) model leads to unusually large spin parameters in the range of lambda=0.05-0.2. In addition, the ratios of disk-to-dark halo masses md are extreme and in several cases exceed the cosmic baryon fraction. The galaxies segregate into dispersion-dominated systems with 1200 km/s, vmax/sigma>3 and rd=4-8 kpc. For the dispersion-dominated sample, radial pressure gradients partly compensate the gravitational force, reducing the rotational velocities. Including this pressure effect in the MMW model leads to spin parameters lambda=0.035 and disk mass fractions md=0.1 that are in good agreement with cosmological expectations. For the rotation-dominated sample, pressure effects are small and better agreement with theoretical expectations can only be achieved if the da...
Baryon resonances in a chiral confining model, 1
Umino, Y
1998-01-01
In this two part series a chiral confining model of baryons is used to describe low--lying negative parity resonances $N^*$, $\\Delta^*$, $\\Lambda^*$ and $\\Sigma^*$ in the mean field approximation. A physical baryon in this model consists of interacting valence quarks, mesons and a color and chiral singlet hybrid field coexisting inside a dynamically generated confining region. This first paper presents the quark contribution to the masses and wave functions of negative parity baryons calculated with an effective spin--isospin dependent instanton induced interaction. It does not include meson exchanges between quarks. The three--quark wave functions are used to calculate meson--excited baryon vertex functions to lowest order in meson--quark coupling. When the baryons are on mass--shell each of these vertex functions is a product of a coupling constant and a form factor. As examples, quark contributions to $N^*$ hadronic form factors as well as axial coupling constants are extracted from the vertex functions an...
Perturbative QCD and electromagnetic form factors
We calculate nucleon magnetic form factors using perturbative QCD for several distribution amplitudes including a general one given in terms of Appell polynomials. We find that the magnitude and sign of both nucleon magnetic form factors can be explained within perturbative QCD. The observed normalization of G/sub Mp/ requires that the distribution amplitude be broader than its superhigh momentum transfer limit, and the G/sub Mn//G/sub Mp/ data may require the distribution amplitude to be asymmetric, in accord with distribution amplitudes derived from QCD sum rules. Some speculation as to how an asymmetric distribution amplitude can come about is offered. Finally, we show that the soft contributions corresponding to the particular distribution amplitudes we use need not be bigger than the data. 16 refs., 6 figs
Nucleon form factors. Probing the chiral limit
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
Form factors in theories with gravity duals
The prescription for calculating form factors at strong coupling in the theories with gravity duals was found in [L. F. Alday, J. Maldacena, JHEP 0711, 068 (2007). (arXiv:0710.1060 [hep-th])]. The use of integrability for similar objects culminated in the paper [L. F. Alday, J. Maldacena, A. Sever, P. Vieira, J. Phys. A A43, 485401 (2010). (arXiv:1002.2459 [hep-th])] where the Y-system for scattering amplitudes was found. In the paper [J. Maldacena, A. Zhiboedov, JHEP 1011, 104 (2010). (arXiv:1009.1139 [hep-th])] authors extended this scenario to the case of form factors in AdS3 kinematics. Some exact solutions were present. Here we briefly review the results of [J. Maldacena, A. Zhiboedov, JHEP 1011, 104 (2010). (arXiv:1009.1139 [hep-th])] and later developments of the problem.
Form factors of heavy mesons in QCD
Logarithmic corrections to form factors of mesons built from heavy quarks are dirived in the framework of quantum chromodynamics. The reactions e+e- → etasub(c)γ and H → J/PSIγ are considered as an example. A novel feature as compared to the well studied problem of the pion form factor is the existence of the transformations between the quark-antiquark state c anti c and the gluonic one. O(αsub(s)) corrections are calculated exactly. An infinite series of the leading logarithmic terms is summed up with the help of the operator technique. Apart from already known results for quark operators some new results referring to gluon operators and their mixing with the quark ones are used. Two alternative derivations of the multiplicatively renormalizable operators are given. The first one reduces to a direct computation of the mixing matrix and its diagonalization, the second derivation is based on conformal symmetry considerations
Nucleon form factors. Probing the chiral limit
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Dept.; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2006-10-15
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
CALCULATION OF KAON ELECTROMAGNETIC FORM FACTOR
WANG ZHI-GANG; WAN SHAO-LONG; WANG KE-LIN
2001-01-01
The kaon meson electromagnetic form factor is calculated in the framework of coupled Schwinger-Dyson and Bethe-Salpeter formulation in simplified impulse approximation (dressed vertex) with modified fiat-bottom potential,which is a combination of the flat-bottom potential taking into consideration the infrared and ultraviolet asymptotic behaviours of the effective quark-gluon coupling. All the numerical results give a good fit to experimental values.
Elastic form factors at higher CEBAF energies
Petratos, G.G. [Kent State Univ., OH (United States)
1994-04-01
The prospects for elastic scattering from few body systems with higher beam energies at CEBAF is presented. The deuteron and{sup 3}He elastic structure functions A(Q{sup 2}) can be measured at sufficiently high momentum transfers to study the transition between the conventional meson-nucleon and the constituent quark-gluon descriptions. Possible improvements in the proton magnetic form factor data are also presented.
FORM FACTOR MEASUREMENT IN FERROMAGNETIC COBALT ORTHOVANADATE
Fuess, H.; Müller, R.; Schwabe, D.; Tasset, F.
1982-01-01
Single crystals of cobalt orthovanadate Co3V2O8 were grown by the Czochralski method. The substance is orthorhombic with two different crystallographic sites for the cobalt ions. Magnetization measurements in fields up to 15 Tesla show pronounced magnetic anisotropy and a ferromagnetic ordering below Tc = 6.3 (3)K. Neutron powder pattern and polarized measurements on a single crystal revealed different magnetic moments for the two cobalt ions. The analysis of the magnetic form factors gave th...
Towards a four-loop form factor
Boels, Rutger; Yang, Gang
2016-01-01
The four-loop, two-point form factor contains the first non-planar correction to the lightlike cusp anomalous dimension. This anomalous dimension is a universal function which appears in many applications. Its planar part in N = 4 SYM is known, in principle, exactly from AdS/CFT and integrability while its non-planar part has been conjectured to vanish. The integrand of the form factor of the stress-tensor multiplet in N = 4 SYM including the non-planar part was obtained in previous work. We parametrise the difficulty of integrating this integrand. We have obtained a basis of master integrals for all integrals in the four-loop, two-point class in two ways. First, we computed an IBP reduction of the integrand of the N = 4 form factor using massive computer algebra (Reduze). Second, we computed a list of master integrals based on methods of the Mint package, suitably extended using Macaulay2 / Singular. The master integrals obtained in both ways are consistent with some minor exceptions. The second method indic...
Magnetic form factor studies of actinide compounds
Some results obtained at ILL on Actinide compound form factors are reviewed. In the paramagnetic NpO2 single crystal (5mg), an induced magnetic moment of 0.07μsub(B) was obtained at 4.2K (4.6T). In the ferromagnetic phase of NpAs2 single crystal (0.2mm3), the magnetic moment (1.46μsub(B)/Np atom) has been found fixed along the [001] direction. In both cases, the Np form factors fit satisfactorily the Np4+ form factor calculated with relativistic atomic wave functions. The Fermi length for Np was deduced (b(Np) = 1.015(15)10-12cm). In the paramagnetic Laves phase UNi2 compound, equally small moments are observed on U atom (0.013(1)μsub(B)) and on Ni atom (0.016(1)μsub(B)) confirming important changes in 3d band structure of Ni by hybridization with U electrons
Time-like Baryon Form Factors near threshold: status and perspectives
Baldini Ferroli, Rinaldo [Museo Storico della Fisica e Centro Studi e Ricerche ' E. Fermi' , Rome (Italy); INFN, Laboratori Nazionali di Frascati, Frascati (Italy); Pacetti, Simone [University and INFN of Perugia, Perugia (Italy); Zallo, Adriano [INFN, Laboratori Nazionali di Frascati, Frascati (Italy)
2011-10-15
Two striking features of the e{sup +}e{sup -}{yields}pp{sup Macron} and e{sup +}e{sup -}{yields}nn{sup Macron} cross sections near threshold are discussed: the e{sup +}e{sup -}{yields}pp{sup Macron} data show a nearly flat cross section in the 200 MeV region above threshold. The e{sup +}e{sup -}{yields}nn{sup Macron} results, published in 1998 by the FENICE collaboration at ADONE collider, show a neutron cross section larger or equal to the proton one. This surprising behavior has been confirmed recently by SND experiment at VEPP-2000. The FENICE and SND results have been obtained with energy scan measurements, while for the BABAR data the initial state radiation technique has been used. This technique has a high efficiency even at the production threshold and appears to be the best solution to a better understanding of these behaviors. To this purpose the zero degree photon detector, now in the installation stage with BESIII experiment at BEPCII collider, has been constructed. A preliminary analysis on the improvements achievable with this detector is presented.
Baryon mapping of quark systems
Sambataro, M
1995-01-01
We discuss a mapping procedure from a space of colorless three-quark clusters into a space of elementary baryons and illustrate it in the context of a three-color extension of the Lipkin model recently developed. Special attention is addressed to the problem of the formation of unphysical states in the mapped space. A correspondence is established between quark and baryon spaces and the baryon image of a generic quark operator is defined both in its Hermitian and non-Hermitian forms. Its spectrum (identical in the two cases) is found to consist of a physical part containing the same eigenvalues of the quark operator in the cluster space and an unphysical part consisting only of zero eigenvalues. A physical subspace of the baryon space is also defined where the latter eigenvalues are suppressed. The procedure discussed is quite general and applications of it can be thought also in the correspondence between systems of 2n fermions and n bosons.
The structure of a sample of high-redshift (z ∼ 2), rotating galaxies with high star formation rates and turbulent gas velocities of σ ∼ 40-80 km s-1 is investigated. Fitting the observed disk rotational velocities and radii with a Mo et al. (MMW) model requires unusually large disk spin parameters λd>0.1 and disk-to-dark halo mass fractions of md ∼ 0.2, close to the cosmic baryon fraction. The galaxies segregate into dispersion-dominated systems with 1 ≤ vmax/σ ≤ 3, maximum rotational velocities vmax≤ 200 km s-1, and disk half-light radii r1/2∼ 1-3 kpc, and rotation-dominated systems with vmax> 200 km s-1, vmax/σ>3, and r1/2∼ 4-8 kpc. For the dispersion-dominated sample, radial pressure gradients partly compensate the gravitational force, reducing the rotational velocities. Including this pressure effect in the MMW model, dispersion-dominated galaxies can be fitted well with spin parameters of λd = 0.03-0.05 for high disk mass fractions of md ∼ 0.2 and with λd = 0.01-0.03 for md ∼ 0.05. These values are in good agreement with cosmological expectations. For the rotation-dominated sample, however, pressure effects are small and better agreement with theoretically expected disk spin parameters can only be achieved if the dark halo mass contribution in the visible disk regime (2-3 x r1/2) is smaller than predicted by the MMW model. We argue that these galaxies can still be embedded in standard cold dark matter halos if the halos do not contract adiabatically in response to disk formation. In this case, the data favor models with small disk mass fractions of md = 0.05 and disk spin parameters of λd ∼ 0.035. It is shown that the observed high turbulent gas motions of the galaxies are consistent with a Toomre instability parameter Q = 1 which is equal to the critical value, expected for gravitational disk instability to be the major driver of turbulence. The dominant energy source of turbulence is then the potential energy of the gas in the
Higgs form factors in associated production
We further develop a form factor formalism characterizing anomalous interactions of the Higgs-like boson (h) to massive electroweak vector bosons (V) and generic bilinear fermion states (F). Employing this approach, we examine the sensitivity of pp→F→Vh associated production to physics beyond the Standard Model, and compare it to the corresponding sensitivity of h→VF decays. We discuss how determining the Vh invariant-mass distribution in associated production at LHC is a key ingredient for model-independent determinations of hVF interactions. We also provide a general discussion about the power counting of the form factor’s momentum dependence in a generic effective field theory approach, analyzing in particular how effective theories based on a linear and non-linear realization of the SU(2)L×U(1)Y gauge symmetry map into the form factor formalism. We point out how measurements of the differential spectra characterizing h→VF decays and pp→F→Vh associated production could be the leading indication of the presence of a nonlinear realization of the SU(2)L×U(1)Y gauge symmetry
Lambda_b -> Lambda l+ l- form factors and differential branching fraction from lattice QCD
Detmold, William; Meinel, Stefan; Wingate, Matthew
2012-01-01
We present the first lattice QCD determination of the $\\Lambda_b \\to \\Lambda$ transition form factors that govern the rare baryonic decays $\\Lambda_b \\to \\Lambda l^+ l^-$ at leading order in heavy-quark effective theory. Our calculations are performed with 2+1 flavors of domain-wall fermions, at two lattice spacings and with pion masses down to 227 MeV. Three-point functions with a wide range of source-sink separations are used to extract the ground-state contributions. The form factors are extrapolated to the physical values of the light-quark masses and to the continuum limit. We use our results to calculate the differential branching fractions for $\\Lambda_b \\to \\Lambda l^+ l^-$ with $l=e,\\mu,\\tau$ within the standard model. We find agreement with a recent CDF measurement of the $\\Lambda_b \\to \\Lambda \\mu^+ \\mu^-$ differential branching fraction.
Large-distance properties of holographic baryons
Employing the asymptotic instanton solution in an arbitrary background of a set of holographic QCD models, we show that baryon form factors have a precise large-distance behavior regardless of the background. The dependence coincides with that obtained from general chiral soliton models and large-NC chiral perturbation theory. The nonlinear terms in the equations of motion are necessary to recover the correct results. We also show that the holographic currents have the right structure at low energy if the solutions of the full equation of motion, instead of the linearized ones, are used. The indication is that in this holographic approach, the linearized approximation used in the meson sector is not appropriate for the solitonic description of the baryons
Electric Form Factor of the Neutron
Feuerbach, Robert
2007-10-13
Recent polarization-based precision measurements of the nucleons' elastic electric form factors have led to surprising results. The measurement of the ratio of the proton's electromagnetic form factors, $\\mu_p G_E^p/G_M^p$, was found to drop nearly linearly with $Q^2$ out to at least $5 \\mathrm{GeV}^2$, inconsistent with the older Rosenbluth-type experiments. A recent measurement of $G_E^n$, the neutron's electric form-factor saw $G_E^n$ does not fall off as quickly as commonly expected up to $Q^2 \\approx 1.5 \\mathrm{GeV}^2$. Extending this study, a precision measurement of $G_E^n$ up to $Q^2=3.5 \\mathrm{GeV}^2$ was completed in Hall A at Jefferson Lab. The ratio $G_E^n/G_M^n$ was measured through the beam-target asymmetry $A_\\perp$ of electrons quasi-elastically scattered off polarized neutrons in the reaction ${}^{3}\\overrightarrow{He}(\\overrightarrow{e},e' n)$. The experiment took full advantage of the electron beam, recent target developments, as well as two detectors new to Jefferson Lab. The measurement used the accelerator's 100\\% duty-cycle high-polarization (typically 84\\%) electron beam and a new, hybrid optically-pumped polarized ${}^{3}\\overrightarrow{He}$ target which achieved in-beam polarizations in excess of 50\\%. A medium acceptance (80msr) open-geometry magnetic spectrometer (BigBite) detected the scattered electron, while a geometrically matched neutron detector observed the struck neutron. Preliminary results from this measurement will be discussed and compared to modern calculations of $G_E^n$.
Neutron electric form factor via recoil polarimetry
The ratio of the electric to the magnetic form factor of the neutron, GEn/GMn, was measured via recoil polarimetry from the quasielastic d((pol-e),e(prime)(pol-n)p) reaction at three values of Q2 [viz., 0.45, 1.15 and 1.47 (GeV/c)2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that GEn follows the Galster parameterization up to Q2 = 1.15 (GeV/c)2 and appears to rise above the Galster parameterization at Q2 = 1.47 (GeV/c)2
Neutron electric form factor via recoil polarimetry
Madey, Richard; Semenov, Andrei; Taylor, Simon; Aghalaryan, Aram; Crouse, Erick; MacLachlan, Glen; Plaster, Bradley; Tajima, Shigeyuki; Tireman, William; Yan, Chenyu; Ahmidouch, Abdellah; Anderson, Brian; Asaturyan, Razmik; Baker, O; Baldwin, Alan; Breuer, Herbert; Carlini, Roger; Christy, Michael; Churchwell, Steve; Cole, Leon; Danagoulian, Samuel; Day, Donal; Elaasar, Mostafa; Ent, Rolf; Farkhondeh, Manouchehr; Fenker, Howard; Finn, John; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Howell, Calvin; Hu, Bitao; Jones, Mark; Kelly, James; Keppel, Cynthia; Khandaker, Mahbubul; Kim, Wooyoung; Kowalski, Stanley; Lung, Allison; Mack, David; Manley, D; Markowitz, Pete; Mitchell, Joseph; Mkrtchyan, Hamlet; Opper, Allena; Perdrisat, Charles; Punjabi, Vina; Raue, Brian; Reichelt, Tilmann; Reinhold, Joerg; Roche, Julie; Sato, Yoshinori; Seo, Wonick; Simicevic, Neven; Smith, Gregory; Stepanyan, Samuel; Tadevosyan, Vardan; Tang, Liguang; Ulmer, Paul; Vulcan, William; Watson, John; Wells, Steven; Wesselmann, Frank; Wood, Stephen; Yan, Chen; Yang, Seunghoon; Yuan, Lulin; Zhang, Wei-Ming; Zhu, Hong Guo; Zhu, Xiaofeng
2003-05-01
The ratio of the electric to the magnetic form factor of the neutron, G_En/G_Mn, was measured via recoil polarimetry from the quasielastic d({pol-e},e'{pol-n)p reaction at three values of Q^2 [viz., 0.45, 1.15 and 1.47 (GeV/c)^2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G_En follows the Galster parameterization up to Q^2 = 1.15 (GeV/c)^2 and appears to rise above the Galster parameterization at Q^2 = 1.47 (GeV/c)^2.
The effect of antisymmetrization in diquark models of baryons
The effect of antisymmetrization in diquark models of baryons composed of light (u and d) quarks is investigated. The diquark in this study is considered alternately as a point-like and as a composite particle where antisymmetrization is taken into account by means of Generator Coordinate Model operator kernels. The effect on ground state masses and form factors is striking and we are able to conclude that there is a strong dynamical effect due to the presence of antisymmetrization in diquark models of baryon. (author)
Extended-soft-core Baryon-Baryon Model ESC08 I. Nucleon-Nucleon Scattering
Nagels, M M; Yamamoto, Y
2014-01-01
The Nijmegen extended-sft-core ESC08c model for the baryon-baryon (BB) interactions of the SU(3) flavor-octet of baryons ($N, \\Lambda, \\Sigma$, and $\\Xi$) is presented. In this first of a series of papers, the NN results are reported in detail. In the spirit of the Yukawa-approach to the nuclear force problem, the interactions are studied from the meson-exchange picture viewpoint, using generalized soft-core Yukawa-functions. These interactions are supplemented with (i) multiple-gluon-exchange, and (ii) structural effects due to the quark-core of the baryons. The extended-soft-core (ESC) meson-exchange interactions consist of local- and non-local-potentials due to ((i) One-boson-exchanges (OBE, which are the members of nonets of pseudoscalar , vector, scalar, and axial-vector mesons, (ii) diffractive (i.e. multiple-gluon) exchanges, (iii) two pseudoscalar exchange (PS-PS), and (iv) meson-pair-exchange (MPE). The OBE- and MPE-vertices are regulated by gaussian form factors producing potentials with a soft beha...
Helium Compton Form Factor Measurements at CLAS
Voutier, Eric
2013-01-01
The distribution of the parton content of nuclei, as encoded via the generalized parton distributions (GPDs), can be accessed via the deeply virtual Compton scattering (DVCS) process contributing to the cross section for leptoproduction of real photons. Similarly to the scattering of light by a material, DVCS provides information about the dynamics and the spatial structure of hadrons. The sensitivity of this process to the lepton beam polarization allows to single-out the DVCS amplitude in terms of Compton form factors that contain GPDs information. The beam spin asymmetry of the $^4$He($\\vec {\\mathrm e}$,e$' \\gamma ^4$He) process was measured in the experimental Hall B of the Jefferson Laboratory to extract the real and imaginary parts of the twist-2 Compton form factor of the $^4$He nucleus. The experimental results reported here demonstrate the relevance of this method for such a goal, and suggest the dominance of the Bethe-Heitler amplitude to the unpolarized process in the kinematic range explored by th...
Recent results on neutron electromagnetic form factors
The magnetic form factor Gmn was measured via the ratio of cross sections R = σD(e,e'n)/σD(e,e'p) on the deuteron in the q2-range 0.07-0.90 (GeV/c)2 with high precision at the Mainz Microtron. In the ratio R the dependence on the deuteron structure cancels and the sensitivity to meson exchange currents and final state interactions is small. The efficiency of the detector was measured at the high intensity neutron beam of Paul Scherrer Institute. We have also determined the electric form factor of the neutron Gen via H-vector,(e-vector,e'n) in quasi-elastic kinematics at 0.67 (GeV/c)2. Gen is extracted from the asymmetry ratio Aperpendicular/Aparallel which is measured with target spin perpendicular and parallel to the momentum transfer. Due to the dominance of the interference term Gmn Gen this method provides a high sensitivity to the small quantity Gen
Baryons as relativistic three-quark bound states
Eichmann, Gernot; Williams, Richard; Alkofer, Reinhard; Fischer, Christian S
2016-01-01
We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon proce...
Full text: The suppression of single, nonphotonic electrons at RHIC has been usually attributed to heavy-quark energy losses. However, calculations that successfully describe the nuclear modification factor for hadrons fail to describe the single, nonphotonic electron modification factor RAAe. This has prompted a great deal of effort aimed to describe the heavy-quark energy-loss mechanisms but also, in a complementary approach, the study of mechanisms able to produce an enhancement in the heavy-baryon to heavy-meson ratio. We show that the single, nonphotonic electron nuclear modification factor RAAe is affected by the thermal enhancement of the heavy-baryon to heavy-meson ratio in relativistic heavy-ion collisions, with respect to proton proton collisions. We use a dynamical quark recombination model to compute such a ratio and show that this produces a sizable suppression factor for RAAe at intermediate transverse momenta. We argue that this suppression factor has to be considered, in addition to the energy loss contribution, in calculations of RAAe. (author)
Holography, chiral Lagrangian and form factor relations
Zuo, Fen
2013-01-01
We perform a detailed study of mesonic properties in a class of holographic models of QCD, which is described by the Yang-Mills plus Chern-Simons action. By decomposing the 5 dimensional gauge field into resonances and integrating out the massive ones, we reproduce the Chiral Perturbative Theory Lagrangian up to ${\\cal O}(p^6)$ and obtain all the relevant low energy constants (LECs). The numerical predictions of the LECs show minor model dependence, and agree reasonably with the determinations from other approaches. Interestingly, various model-independent relations appear among them. Some of these relations are found to be the large-distance limits of universal relations between form factors of the anomalous and even-parity sectors of QCD.
Measurement of the neutron magnetic form factor
The ratio of neutron and proton yields at quasifree kinematics was measured for the reactions 2H(e,e'n) and 2H(e,e'p) at momentum transfers Q2=0.125, 0.255, 0.417, and 0.605(GeV/c)2, detecting the neutron and the proton simultaneously in the same scintillator array. The neutron detection efficiency was measured in situ with the 1H(γ,π+)n reaction. From this the ratio R of 2H(e,e'n) and 2H(e,e'p) cross sections was determined and used to extract the neutron magnetic form factor GnM in a model insensitive approach, resulting in an inaccuracy between 2.1% and 3.3% in GnM
Elastic and Transition Form Factors in DSEs
Segovia, Jorge
2016-06-01
A symmetry preserving framework for the study of continuum quantum chromodynamics (QCD) is obtained from a truncated solution of the QCD equations of motion or QCD's Dyson-Schwinger equations (DSEs). A nonperturbative solution of the DSEs enables the study of, e.g., hadrons as composites of dressed-quarks and dressed-gluons, the phenomena of confinement and dynamical chiral symmetry breaking, and therefrom an articulation of any connection between them. It is within this context that we present a unified study of Nucleon, Delta and Roper elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector ⊗ vector contact-interaction.
Elastic and Transition Form Factors in DSEs
Segovia, Jorge
2016-01-01
A symmetry preserving framework for the study of continuum Quantum Chromodynamics (QCD) is obtained from a truncated solution of the QCD equations of motion or QCD's Dyson-Schwinger equations (DSEs). A nonperturbative solution of the DSEs enables the study of, e.g., hadrons as composites of dressed-quarks and dressed-gluons, the phenomena of confinement and dynamical chiral symmetry breaking (DCSB), and therefrom an articulation of any connection between them. It is within this context that we present a unified study of Nucleon, Delta and Roper elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector$\\,\\otimes\\,$vector contact-interaction.
Peters, Gerhard
2008-05-15
In this work the leading-twist next-to-leading order (NLO) correction to the light-cone sum rules prediction for the electromagnetic form factors of the nucleon are calculated. Here the Ioffe nucleon interpolation current is used and it is worked in the M{sub N}=0 approximation, with M{sub N} being the mass of the nucleon. In this approximation, only the Pauli form factor F{sub 2} receives a correction and the calculated correction is quite sizable. The numerical results for the proton form factors show the improved agreement with the experimental data. Furthermore the problems encountered when going away from M{sub N}=0 approximation at NLO, as well as, gauge invariance of the perturbative results are discussed. This work presents the first step towards the NLO accuracy in the light-cone sum rules for baryon form factors. (orig.)
The good, the bad, and the baryon
We describe the incorporation of baryons into an effective theory of QCD at low energies. The baryon is not a Skyrmion, rather it consists of three valence quarks bound by effective gluon exchanges, enveloped in a meson cloud, which may possibly take the form of a chiral soliton. Some of the physical implications of these results are also discussed. (orig.)
The Dirac form factor predicts the Pauli form factor in the Endpoint Model
Dagaonkar, Sumeet K.; Jain, Pankaj; Ralston, John P.
2016-07-01
We compute the momentum-transfer dependence of the proton Pauli form factor F2 in the Endpoint overlap Model. We find the model correctly reproduces the scaling of the ratio of F2 with the Dirac form factor F1 observed at the Jefferson Laboratory. The calculation uses the leading-power, leading-twist Dirac structure of the quark light-cone wave function and the same endpoint dependence previously determined from the Dirac form factor F1. There are no parameters and no adjustable functions in the Endpoint Model's prediction for the scaling behavior of F2. The model's predicted momentum dependence of the ratio F2(Q2)/F1(Q2) is quite insensitive to the endpoint wave function, which explains why the observed ratio scales like 1 / Q down to rather low momentum transfers. We also fit the magnitude of this ratio by adjusting the parameters of the wave function. The Endpoint Model appears to be the only comprehensive model consistent with all form factor information as well as reproducing fixed-angle proton-proton scattering at large momentum transfer. Any one of the processes is capable of predicting the others.
Proton spin and baryon octet axial couplings
Peripheral spin structure of the nucelon generated by the soft mesonic radiative corrections is studied within the light-cone perturbation theory. Starting with the tree-level SU(6) symmetry, we find a good description of the axial-vector couplings in β-decay of hyperons. We study the proton helicity flow from the baryonic core to the angular momentum of the pionic cloud. It is found that in the relativistic light-cone approach the spin-flip pattern is different from that in the coventional non-relativistic models. The axial-vector current matrix elements are shown to receive large corrections from beyond the conventional static limit. The important virtue of using the light-cone vertex functions of the meson-baryon Fock components of the proton is that the local gauge invariance and the energy-momentum sum rule are satisfied automatically. We infer the radius of the light-cone form factor from an analysis of the experimental data on the fragmentation of high-energy protons into nucleons and hyperons-the process dominated by stripping off the mesons of the meson-baryon Fock states. (orig.)
Octet baryon magnetic moments in light cone QCD sum rules
Aliev, T M; Özpineci, A
2002-01-01
Octet baryon magnetic moments are calculated in framework of the light cone QCD sum rules. The analysis is carried for the general form of the interpolating currents for octet baryons. A comparison of our results on the magnetic moments of octet baryons with the predictions of other approaches and experimental data is presented.
SU(3) flavour breaking and baryon structure
Cooke, A.N.; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe, Hyogo (Japan); Pleiter, D. [Forschungszentrum Juelich GmbH (Germany). Juelich Supercomputing Centre (JSC); Regensburg Univ. (Germany). Institut fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Shanahan, P.; Zanotti, J.M. [Adelaide Univ., SA (Australia). CSSM, School of Chemistry and Physics; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stueben, H. [Hamburg Univ. (Germany). Regionales Rechenzentrum; Collaboration: QCDSF/UKQCD Collaboration
2013-11-15
We present results from the QCDSF/UKQCD collaboration for hyperon electromagnetic form factors and axial charges obtained from simulations using N{sub f}=2+1 flavours of O(a)-improved Wilson fermions. We also consider matrix elements relevant for hyperon semileptonic decays. We find flavour-breaking effects in hyperon magnetic moments which are consistent with experiment, while our results for the connected quark spin content indicates that quarks contribute more to the spin of the {Xi} baryon than they do to the proton.
Quasinuclear states in baryon-antibaryon systems
A review of modern state of physics of quasinuclear baryon-antibarion systems (''baryonium'') is presented. The comparison between the theory predictions and recent experimental data is carried out. Discrete γ - spectrum from the anti pp annihilation, annihilation and elastic widths for N anti N resonances from experiments with hydrogen and deuterium targets, proton form factor and e+e- annihilation in the vicinity of N anti N threshold are considered. The most important future experiments on antiproton annihilation in nuclear targers are discussed. Experiments which may reveal the existences of 2B anti B and 2B anti 2B systems are predicted
Explicit boundary form factors: The scaling Lee–Yang model
Hollo, L. [MTA Lendület Holographic QFT Group, Wigner Research Centre for Physics, P.O.B. 49, H-1525 Budapest 114 (Hungary); Laczko, Z.B. [Roland Eötvös University, Pázmány Péter sétány 1/A, 1117 Budapest (Hungary); Bajnok, Z. [MTA Lendület Holographic QFT Group, Wigner Research Centre for Physics, P.O.B. 49, H-1525 Budapest 114 (Hungary)
2014-09-15
We provide explicit expressions for boundary form factors in the boundary scaling Lee–Yang model for operators with the mildest ultraviolet behavior for all integrable boundary conditions. The form factors of the boundary stress tensor take a determinant form, while the form factors of the boundary primary field contain additional explicit polynomials.
Fukushima, Kenji
2014-01-01
We summarize recent developments in identifying the ground state of dense baryonic matter and beyond. The topics include deconfinement from baryonic matter to quark matter, a diquark mixture, topological effect coupled with chirality and density, and inhomogeneous chiral condensates.
Mass and magnetic dipole moment of negative parity heavy baryons with spin--3/2
Azizi, K
2015-01-01
We calculate the mass and residue of the heavy spin--3/2 negative parity baryons with single heavy bottom or charm quark by the help of a two-point correlation function. We use the obtained results to investigate the diagonal radiative transitions among the baryons under consideration. In particular, we compute corresponding transition form factors via light cone QCD sum rules which are then used to obtain the magnetic dipole moments of the heavy spin--3/2 negative parity baryons. We remove the pollutions coming from the positive parity spin--3/2 and positive/negative parity spin--1/2 baryons by constructing sum rules for different Lorentz structures. We compare the results obtained with the existing theoretical predictions.
de Teramond, Guy F
2016-01-01
The superconformal algebraic approach to hadronic physics is used to construct a semiclassical effective theory for nucleons which incorporates essential nonperturbative dynamical features, such as the emergence of a confining scale and the Regge resonance spectrum. Relativistic bound-state equations for nucleons follow from the extension of superconformal quantum mechanics to the light front and its holographic embedding in a higher dimensional gravity theory. Superconformal algebra has been used elsewhere to describe the connections between the light mesons and baryons, but in the present context it relates the fermion positive and negative chirality states and uniquely determines the confinement potential of nucleons. The holographic mapping of multi-quark bound states also leads to a light-front cluster decomposition of form factors for an arbitrary number of constituents. The remarkable analytical structure which follows incorporates the correct scaling behavior at high photon virtualities and also vecto...
Semileptonic decays of $\\Lambda_b$ baryons in the relativistic quark model
Faustov, R N
2016-01-01
Semileptonic $\\Lambda_b$ decays are investigated in the framework of the relativistic quark model based on the quasipotential approach and the quark-diquark picture of baryons. The decay form factors are expressed through the overlap integrals of the initial and final baryon wave functions. All calculations are done without employing nonrelativistic and heavy quark expansions. The momentum transfer dependence of the decay form factors is explicitly determined in the whole accessible kinematical range without any extrapolations or model assumptions. Both the heavy-to-heavy $\\Lambda_b\\to\\Lambda_c\\ell\
The pion form factor from analyticity and unitarity
B Ananthanarayan; Irinel Caprini; I Sentitemsu Imsong
2012-11-01
Analyticity and unitarity techniques are employed to estimate Taylor coefficients of the pion electromagnetic form factor at = 0 by exploiting the recently evaluated two-pion contribution to the muon ( − 2) and the phase of the pion electromagnetic form factor in the elastic region, known from scattering by Fermi–Watson theorem and the values of the form factor at several points in the space-like region. Regions in the complex -plane are isolated where the form factor cannot have zeros.
Nucleon electromagnetic form factors and axial charge from CLS $N_\\mathrm{f}=2+1$ ensembles
Djukanovic, Dalibor; von Hippel, Georg; Junnarkar, Parikshit; Meyer, Harvey B; Wittig, Hartmut
2015-01-01
We present preliminary results on the electromagnetic form factors and axial charge of the nucleon from ensembles generated by the CLS effort with $N_\\mathrm{f}=2+1$ flavours of non-perturbatively $\\mathrm{O}(a)$-improved Wilson fermions and open temporal boundary conditions. Systematic effects due to excited-state contamination are accounted for using both two-state fits and the method of summed operator insertions. This exploratory analysis demonstrates the viability of obtaining precision baryon observables with $N_\\mathrm{f}=2+1$ flavours of Wilson fermions on fine lattices, aiming towards controlled chiral and continuum limits in the future.
Exclusive c → s, d Semileptonic Decays of Spin-1/2 and Spin-3/2 cb Baryons
We present results for exclusive semileptonic decay widths of ground state spin-1/2 and spin-3/2 cb baryons corresponding to a c → s, d transition at the quark level. The relevance of hyperfine mixing in spin-1/2 cb baryons is shown. Our form factors are compatible with heavy quark spin symmetry constraints obtained in the infinite heavy quark mass limit. (author)
Dynamically generated baryon resonances
Lutz, M F M
2005-01-01
Identifying a zero-range exchange of vector mesons as the driving force for the s-wave scattering of pseudo-scalar mesons off the baryon ground states, a rich spectrum of molecules is formed. We argue that chiral symmetry and large-$N_c$ considerations determine that part of the interaction which generates the spectrum. We suggest the existence of strongly bound crypto-exotic baryons, which contain a charm-anti-charm pair. Such states are narrow since they can decay only via OZI-violating processes. A narrow nucleon resonance is found at mass 3.52 GeV. It is a coupled-channel bound state of the $(\\eta_c N), (\\bar D \\Sigma_c)$ system, which decays dominantly into the $(\\eta' N)$ channel. Furthermore two isospin singlet hyperon states at mass 3.23 GeV and 3.58 GeV are observed as a consequence of coupled-channel interactions of the $(\\bar D_s \\Lambda_c), (\\bar D \\Xi_c)$ and $(\\eta_c \\Lambda),(\\bar D \\Xi_c')$ states. Most striking is the small width of about 1 MeV of the lower state. The upper state may be signi...
Virtuality Distributions and Pion Transition Form Factor
Radyushkin, A. V.
2015-02-01
Using the example of hard exclusive transition process γ*γ → π0 at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal 𝒪(0, z)) describing a hadron with momentum p, are functions of (pz) and z2 parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+ = 0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k⊥), and write it in terms of VDA Φ(x, σ). We propose models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data. We also discuss the generation of hard tails of TMDAs from initially soft forms.
Magnetic form factors of rare earth ions
The magnetic scattering of neutrons by atoms has been investigated by exploiting its similarity to the radiation problem in spectroscopy. Expressions for the magnetic scattering amplitude were developed for cases in whcih an atom in the l/sup n/ electronic configuration is described either by a relativistic or nonrelativistic Hamiltonian. For each of these cases, it has been shown that the magnetic scattering amplitude can be expressed in terms of relativistic or nonrelativistic matrix elements of magnetic and electric multipole operators. For a nonrelativistic atom, the calculation of these matrix elements has been separated into evaluating radial matrix elements and matrix elements of Racah tensors W/(sup 0,k)k/ and W/(sup 1,k')k/. For a relativistic atom the effective operator approach has been used to define effective multipole operators so that a relativistic result is obtained by taking matrix elements of these effective operators between nonrelativistic states of the atom. The calculation of matrix elements of these effective operators has been reduced to evaluating relativistic radial integrals and matrix elements of the Racah tensors taken between nonrelativistic states of the atom. It is shown tha for the case of elastic scattering by either a relativistic or nonrelativistic atom in single Russel-Saunders state, the magnetic scattering amplitude can be written in the conventional form p(vector q)vector q/sub m/.vector sigma. General expressions for p(vector q) as well as elastic magnetic form factorshave been obtained. The formalism has been illustrated throughout by applying it to the case of scattering by rare earth ions
Study of the baryon-baryon interaction in nucleon-nucleon and pion-deuteron scattering
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
Electromagnetic properties of baryons in the constituent quark model
The electromagnetic properties of baryons are investigated in the framework of a relativized quark model. The model includes beyond the usual single quark transition ansatz relativistic effects due to the strong interaction and confinement forces between the quarks. Furthermore the center-of-mass motion of the three-quark system is separated off in a Lorentz-invariant way. All relativistic correction terms are obtained by expanding the corresponding relativistic expressions in powers of the quark velocity. In this way recoil effects on the electromagnetic interaction between the photon and the baryon could be explicitly studied. Using the harmonic oscillator wavefunctions with the configuration mixing from the Isgur-Karl model, the form factors of the nucleon and the electromagnetic transition amplitudes both for longitudinally and transversely polarized photons are calculated for the most important baryon resonances. An extension to baryons involving strange quarks is also considered. Comparisons are made with the results of the nonrelativistic quark model and with some other approaches. (orig.)
Experiments on strangeness production in nucleus-nucleus collisions at SIS energies address fundamental aspects of modern nuclear physics: the determination of the nuclear equation-of-state at high baryon densities and the properties of hadrons in dense nuclear matter. Experimental data and theoretical results will be reviewed. Future experiments at the FAIR accelerator aim at the exploration of the QCD phase diagram at highest baryon densities. The proposal for the Compressed Baryonic Matter (CBM) experiment will be presented. (author)
Explaining the Dark Energy, Baryon and Dark Matter Coincidence via Domain-Dependent Random Densities
McDonald, John
2013-01-01
The dark energy, dark matter and baryon densities in the Universe are observed to be similar, with a factor of no more than 20 between the largest and smallest densities. We show that this coincidence can be understood via superhorizon domains of randomly varying densities when the baryon density at initial collapse of galaxy-forming perturbations is determined by anthropic selection. The baryon and dark matter densities are assumed to be dependent on random variables \\theta_{d} and \\theta_{b} according to \\rho_{dm} ~ \\theta_{d}^{\\alpha} and \\rho_{b} ~ \\theta_{b}^{\\beta}, while the effectively constant dark energy density is dependent upon a random variable \\phi_{Q} according to \\rho_{Q} ~ \\phi_{Q}^{n}. The ratio of the baryon density to the dark energy density at initial collapse, r_{Q}, and the baryon-to-dark matter ratio, r, are then determined purely statistically, with no dependence on the anthropically-preferred baryon density. We compute the probability distribution for r_{Q} and r and show that the ob...
Electromagnetic properties of light and heavy baryons in the relativistic quark model
Nicmorus Marinescu, Diana
2007-06-14
One of the main challenges of nowadays low-energy physics remains the description of the internal structure of hadrons, strongly connected to the electromagnetic properties of matter. In this vein, the success of the relativistic quark model in the analysis of the hadron structure constitutes a solid motivation for the study carried out throughout this work. The relativistic quark model is extended to the investigation of static electromagnetic properties of both heavy and light baryons. The bare contributions to the magnetic moments of the single-, double- and triple-heavy baryons are calculated. Moreover, the relativistic quark model allows the study of the electromagnetic properties of the light baryon octet incorporating meson cloud contributions in a perturbative manner. The long disputed values of the multipole ratios E2/M1 and C2/M1 and the electromagnetic form factors of the N{yields}{delta}{gamma} transition are successfully reproduced. The relativistic quark model can be viewed as a quantum field theory approach based on a phenomenological Lagrangian coupling light and heavy baryons to their constituent quarks. In our approach the baryon is a composite object of three constituent quarks, at least in leading order. The effective interaction Lagrangian is written in terms of baryon and constituent quark fields. The effective action preserves Lorentz covariance and gauge invariance. The main ingredients of the model are already introduced at the level of the interaction Lagrangian: the three-quark baryon currents, the Gaussian distribution of the constituent quarks inside the baryon and the compositeness condition which sets an upper limit for the baryon-quark vertex. The S-matrix elements are expressed by a set of Feynman quark-diagrams. The model contains only few parameters, namely, the cut-off parameter of the Gaussian quark distribution and the free quark propagator, which are unambiguously determined from the best fit to the data. The heavy quark limit
Electromagnetic properties of light and heavy baryons in the relativistic quark model
One of the main challenges of nowadays low-energy physics remains the description of the internal structure of hadrons, strongly connected to the electromagnetic properties of matter. In this vein, the success of the relativistic quark model in the analysis of the hadron structure constitutes a solid motivation for the study carried out throughout this work. The relativistic quark model is extended to the investigation of static electromagnetic properties of both heavy and light baryons. The bare contributions to the magnetic moments of the single-, double- and triple-heavy baryons are calculated. Moreover, the relativistic quark model allows the study of the electromagnetic properties of the light baryon octet incorporating meson cloud contributions in a perturbative manner. The long disputed values of the multipole ratios E2/M1 and C2/M1 and the electromagnetic form factors of the N→Δγ transition are successfully reproduced. The relativistic quark model can be viewed as a quantum field theory approach based on a phenomenological Lagrangian coupling light and heavy baryons to their constituent quarks. In our approach the baryon is a composite object of three constituent quarks, at least in leading order. The effective interaction Lagrangian is written in terms of baryon and constituent quark fields. The effective action preserves Lorentz covariance and gauge invariance. The main ingredients of the model are already introduced at the level of the interaction Lagrangian: the three-quark baryon currents, the Gaussian distribution of the constituent quarks inside the baryon and the compositeness condition which sets an upper limit for the baryon-quark vertex. The S-matrix elements are expressed by a set of Feynman quark-diagrams. The model contains only few parameters, namely, the cut-off parameter of the Gaussian quark distribution and the free quark propagator, which are unambiguously determined from the best fit to the data. The heavy quark limit within this
Strange magnetic moments of octet baryons under SU(3) breaking
CAO Lu; WANG Biao; CHEN Hong
2012-01-01
Magnetic moments of octet baryons are parameterized to all orders of the flavor SU(3) breaking with the irreducible tensor technique in order to extract the contribution of each flavor quark to the magnetic moments of the octet baryons.The not-yet measured magnetic moment of Σ0 is predicted to be 0.649 μN.Our parameterized forms for the magnetic moments are explicitly flavor-dependent,and hence each flavor component of the magnetic moments can be evaluated directly via the flavor projection operator.It is fouud that the strange magnetic moment of the nucleon is suppressed due to the small isoscalar anomalous magnetic moment of the nucleon.In particular,the strange magnetic form factor of the nucleon turns out to be positive,(G(s)N) (0) =0.428 μN,which is consistent with recent data.
Spectrum of local boundary operators from boundary form factor bootstrap
Szots, M
2007-01-01
Using the recently introduced boundary form factor bootstrap equations, we map the complete space of their solutions for the boundary version of the scaling Lee-Yang model and sinh-Gordon theory. We show that the complete space of solutions, graded by the ultraviolet behaviour of the form factors can be brought into correspondence with the spectrum of local boundary operators expected from boundary conformal field theory, which is a major evidence for the correctness of the boundary form factor bootstrap framework.
Isospin separation of three-nucleon form factors
We have perfromed high-precision measurements of 3He charge and magnetic form factors up to Q2=1 (GeV/c)2. These measurements combined with previous data on 3He and 3H allow us to separate the three-nucleon isospin charge and magnetic form factors up to Q2=1 (GeV/c)2. A large discrepancy between experiment and theory occurs for the T=1 charge form factor
K\\bar{K}-Continuum and Isoscalar Nucleon Form Factors
Hammer, H. -W.; Ramsey-Musolf, M. J.
1999-01-01
We analyse the isoscalar vector current form factors of the nucleon using dispersion relations. In addition to the usual vector meson poles, we account for the K\\bar{K}-continuum contribution by drawing upon a recent analytic continuation of KN scattering amplitudes. For the Pauli form factor all strength in the \\phi region is already given by the continuum contribution, whereas for the Dirac form factor additional strength in the \\phi region is required. The pertinent implications for the le...
Implications of the discrepancy between proton form factor measurements
Arrington, J.
2003-01-01
Recent polarization transfer measurements of the proton electromagnetic form factors yield very different results from previous Rosenbluth extractions. This inconsistency implies uncertainties in our knowledge of the form factors and raises questions about how to best combine data from these two techniques. If the discrepancy is due to missing correction to the cross section data, as has been suggested, then different applications will require the use of different form factors. We present two...
Progress in the calculation of nucleon transition form factors
Eichmann, Gernot
2016-01-01
We give a brief account of the Dyson-Schwinger and Faddeev-equation approach and its application to nucleon resonances and their transition form factors. We compare the three-body with the quark-diquark approach and present a quark-diquark calculation for the low-lying nucleon resonances including scalar, axialvector, pseudoscalar and vector diquarks. We also discuss the timelike structure of transition form factors and highlight the advantages of form factors over helicity amplitudes.
HERMES impact for the access of Compton form factors
Kumerički, K.; Müller, D.; Murray, M.
2014-07-01
We utilize the DVCS asymmetry measurements of the HERMES collaboration for access to Compton form factors in the deeply virtual regime and to generalized parton distributions. In particular, the (almost) complete measurement of DVCS observables allows us to map various asymmetries into the space of Compton form factors, where we still rely in this analysis on dominance of twist-two associated Compton form factors. We compare this one-to-one map with local Compton form factor fits and a model dependent global fit.
HERMES impact for the access of Compton form factors
Kumericki, Kresimir; Murray, Morgan
2013-01-01
We utilize the DVCS asymmetry measurements of the HERMES collaboration for access to Compton form factors in the deeply virtual regime and to generalized parton distributions. In particular, the (almost) complete measurement of DVCS observables allows us to map various asymmetries into the space of Compton form factors, where we still rely in this analysis on dominance of twist-two associated Compton form factors. We compare this one-to-one map with local Compton form factor fits and a model dependent global fit.
Analytical evaluation of atomic form factors: application to Rayleigh scattering
Safari, L; Amaro, P; Jänkälä, K; Fratini, F
2014-01-01
Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wavefunctions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.
Analytical evaluation of atomic form factors: Application to Rayleigh scattering
Safari, L., E-mail: laleh.safari@ist.ac.at [IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg (Austria); Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Santos, J. P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Amaro, P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg (Germany); Jänkälä, K. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Fratini, F. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Institute of Atomic and Subatomic Physics, TU Wien, Stadionallee 2, 1020 Wien (Austria); Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG (Brazil)
2015-05-15
Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.
Diquark model of the baryon spectrum
The presence of a coherent diquark structure within baryons has been suggested, both as a computational tool for simplifying some types of baryon calculations, and as an explanation for scaling violations in deep inelastic scattering. In this paper we consider the implications of the diquark hypothesis for baryons spectroscopy. Treating the diquark as an s-wave bound state of two quarks reduces the problem of three-body quark excitations within baryons to that of a two-body quark-diquark interaction. The spin-dependent excitation levels of the quark-diquark system can then be calculated in perturbative QCD, using a non-relativistic one-gluon-exchange approximation. The spectrum generated by this model differs from the conventional symmetric quark model spectrum in several crucial respects. Firstly, spin-orbit mass splitting between baryons is easily accommodated in the diquark picture, unlike the conventional model, where it must be cancelled ad hoc in order to obtain a reasonable fit to the mass spectrum. Secondly, the QCD parameters needed to fit the baryon spectrum in the diquark model are essentially the same as those used in the meson spectrum. This allows us to give a unified description of spin-dependent forces in mesons and baryons, which has not been possible in the symmetric quark model. We conclude with a qualitative discussion of spin-independent (multiple gluon exchange) forces in the diquark model, using effective confining potentials of the form, V(r) approx. r/sup n/. 28 references
Lattice QCD calculation of form factors for $\\Lambda_b \\to \\Lambda(1520) \\ell^+ \\ell^-$ decays
Meinel, Stefan
2016-01-01
Experimental results for mesonic $b \\to s \\mu^+ \\mu^-$ decays show a pattern of deviations from Standard-Model predictions, which could be due to new fundamental physics or due to an insufficient understanding of hadronic effects. Additional information on the $b \\to s \\mu^+ \\mu^-$ transition can be obtained from $\\Lambda_b$ decays. This was recently done using the process $\\Lambda_b \\to \\Lambda \\mu^+ \\mu^-$, where the $\\Lambda$ is the lightest strange baryon. A further interesting channel is $\\Lambda_b \\to p^+ K^- \\mu^+ \\mu^-$, where the $p^+ K^-$ final state receives contributions from multiple higher-mass $\\Lambda$ resonances. The narrowest and most prominent of these is the $\\Lambda(1520)$, which has $J^P=\\frac32^-$. Here we present an ongoing lattice QCD calculation of the relevant $\\Lambda_b \\to \\Lambda(1520)$ form factors. We discuss the choice of interpolating field for the $\\Lambda(1520)$, and explain our method for extracting the fourteen $\\Lambda_b \\to \\Lambda(1520)$ helicity form factors from corr...
N. Suzuki, T. Sato, T.-S. H. Lee
2010-10-01
We explain the application of a recently developed analytic continuation method to extract the electromagnetic transition form factors for the nucleon resonances ($N^*$) within a dynamical coupled-channel model of meson-baryon reactions.Illustrative results of the obtained $N^*\\rightarrow \\gamma N$ transition form factors, defined at the resonance pole positions on the complex energy plane, for the well isolated $P_{33}$ and $D_{13}$, and the complicated $P_{11}$ resonances are presented. A formula has been developed to give an unified representation of the effects due to the first two $P_{11}$ poles, which are near the $\\pi\\Delta$ threshold, but are on different Riemann sheets. We also find that a simple formula, with its parameters determined in the Laurent expansions of $\\pi N \\rightarrow \\pi N$ and $\\gamma N \\rightarrow\\pi N$ amplitudes, can reproduce to a very large extent the exact solutions of the considered model at energies near the real parts of the extracted resonance positions. We indicate the differences between our results and those extracted from the approaches using the Breit-Wigner parametrization of resonant amplitudes to fit the data.
Form factors, medium effects and vector mesons in the projected chiral soliton model
The main goal of the present work has been the evaluation of baryonic form factors by means of the projected chiralquark-meson soliton model and various generalizations of it. In first place we have studied the Nambu-Jona-Lasinio model in the Hartree approximation for classical non-strange scalar and pseudoscalar couplings in the vacuum sector. In doing so, we have first bosonized the Lagrangian and applied three regularization schemes in order to render the theory finite. We have found that at least two physical quantities as the quark mass and the quark condensate are very sensitive to the actual scheme used. The procedures which allow to reproduce best the experimental values are both sharp cut-off methods. We have also shown that the chiral soliton model with explicit valence quarks can be considered as an approximation to the Hartree solution of the Nambu-Jona-lasinio model for quarks. In the framework of the linear chiral sigma model with quarks, sigma-, and pi-mesons we have discussed several nucleon form factors such as electromagnetic, axial and that for the pion-nucleon interaction. (orig./HSI)
Static-static-light baryonic potentials
Najjar, Johannes; Bali, Gunnar
2009-01-01
We determine doubly heavy baryonic potentials as a function of the distance between the two static sources, coupled to a light relativistic quark, for different quantum numbers. We use the variational method to compute the ground state and the first two excitations. These can be used as an input to nonrelativistic models or to NRQCD calculations of properties of doubly heavy baryons. We compare our findings with a factorization model. We employ all-to-all propagator methods, improved by an ad...
Spectroscopy of beautiful baryons
Caloi, R.; Gentile, S.; Mignani, R. (Rome Univ. (Italy). Ist. di Fisica)
1980-09-20
By assuming a non-relativistic quark model, an estimate of the masses of the low-lying (non-strange and non-charmed) beautiful baryons is given. Electromagnetic mass splittings of the same baryons are also discussed in some detail.
Three body calculations for studying the baryons are performed in a non-relativistic treatment with three quarks interacting via Bhaduri's potential. From the resulting wave functions, it is analysed under which conditions can a diquark structure occurs. Several photos showing quark distributions inside the baryons are presented and discussed in details
Model of separated form factors for unilamellar vesicles
Kiselev, M A; Lesieur, P; Kisselev, A. M.; D. Lombardo; Aksenov, V. L.
2001-01-01
New model of separated form factors is proposed for the evaluation of small-angle neutron scattering curves from large unilamellar vesicles. The validity of the model was checked by comparison to the model of hollow sphere. The model of separated form factors and hollow sphere model give reasonable agreement in the evaluation of vesicle parameters.
Hadron form factors using density-density correlators
Alexandrou, C.; Koutsou, G.; Neff, H.
2006-01-01
Gauge invariant density-density correlators yield detailed information on hadron structure. Hadron deformation and form factors can be extracted for momentum transfers up to about 6 GeV$^2$. We use stochastic techniques and dilution to compute the all to all propagator required for the exact evaluation of density-density correlators. We present first results for the pion form factor.
Unitary bounds on the electromagnetic form factors of pseudoscalar mesons
We investigate the electromagnetic form factors of the π and K mesons using a dispersive technique which exploits perturbative QCD and hadronic unitarity. Constraints on the charge radii and higher Taylor coefficients of the form factors at the origin are derived. The results are of interest for testing the predictions of chiral perturbation theory and of other low energy models. (author)
Nucleon to $\\Delta$ and $\\Delta$ form factors in Lattice QCD
Alexandrou, Constantia
2011-01-01
We present recent lattice QCD results on the electroweak nucleon to $\\Delta$ transition and $\\Delta$ form factors using dynamical fermion gauge configurations with a lowest pion mass of about 300 MeV, with special emphasis in the determination of the sub-dominant quadrupole $N\\gamma^*\\rightarrow \\Delta$ and $\\Delta$ electromagnetic form factors.
X-Ray Form Factor, Attenuation and Scattering Tables
SRD 66 X-Ray Form Factor, Attenuation and Scattering Tables (Web, free access) This database collects tables and graphs of the form factors, the photoabsorption cross section, and the total attenuation coefficient for any element (Z <= 92).
Form factors in SU(3)-invariant integrable models
Belliard, S; Ragoucy, E; Slavnov, N A
2013-01-01
We study SU(3)-invariant integrable models solvable by nested algebraic Bethe ansatz. We obtain determinant representations for form factors of diagonal entries of the monodromy matrix. This representation can be used for the calculation of form factors and correlation functions of the XXX SU(3)-invariant Heisenberg chain.
By using the data accumulated in the DELPHI experiment from 1992 to 1994 we present the results of the production rate measurement of Λc charmed baryons generated in the bb-bar and cc-bar events. For these measurements we reconstructed entirely the Λc baryons decaying in pKπ. Then we select a set of bottom baryons Λb0 by means of its semi-leptonic decays in Λc+l-νl-bar. The study of distribution of these events as a function of the transfer momentum allowed estimating for the first time the slope of the Λb0 form factor. (author)
Spectrum of local boundary operators from boundary form factor bootstrap
Szots, M.; Takacs, G.
2007-01-01
Using the recently introduced boundary form factor bootstrap equations, we map the complete space of their solutions for the boundary version of the scaling Lee-Yang model and sinh-Gordon theory. We show that the complete space of solutions, graded by the ultraviolet behaviour of the form factors can be brought into correspondence with the spectrum of local boundary operators expected from boundary conformal field theory, which is a major evidence for the correctness of the boundary form fact...
Quark model calculation of charmed baryon production by neutrinos
We study the neutrino production of 25 low-lying charmed baryon resonances in the four flavour quark model. The mass difference of ordinary and charmed quarks is explicitly taken into account. The quark model is used to determine the spectrum of the charmed baryon resonances and the q2 = 0 values of the weak current transition matrix elements. These transition matrix elements are then continued to space-like q2-values by a generalized meson dominance ansatz for a set of suitably chosen invariant form factors. We find that the production of the L = 0 states C0, C1 and C1* is dominant, with the C0 produced most copiously. For L = 1, 2 the Jsup(P) = 3/2- 5/2+ charm states are dominant. We give differential cross sections, total cross sections and energy integrated total cross sections using experimental neutrino fluxes. (orig./BJ)
Flavor decomposition of the nucleon electromagnetic form factors
Qattan, I A
2012-01-01
Background: The spatial distribution of charge and magnetization in the proton and neutron are encoded in the nucleon electromagnetic form factors. The form factors are all approximated by a simple dipole function, normalized to the charge or magnetic moment of the nucleon. The differences between the proton and neutron form factors and the deviation of GEn from zero are sensitive to the difference between up- and down-quark contributions to the form factors. Methods: We combine recent measurements of the neutron form factors with updated extractions of the proton form factors, accounting for two-photon exchange corrections and including an estimate of the uncertainties for all of the form factors to obtain a complete set of measurements up to Q^2 approximately 4 (GeV/c)^2. We use this to extract the up- and down-quark contributions which we compare to recent fits and calculations. Results: We find a large differences between the up- and down-quark contributions to G_E and G_M, implying significant flavor dep...
6Li electromagnetic form factors and phenomenological cluster models
The longitudinal form factors of the ground and 2.18 MeV (3+, T = 0) states, and the transverse form factors of the 3.56 MeV (0+, T = 1) and 5.37 MeV (2+, T = 1) states of 6Li are compared with the predictions based on fully antisymmetrized α-d and t-tau cluster models. The longitudinal form factors are adequately described by the α-d model, but the transverse form factors seem to be more consistent with a t-tau model which is close to the shell-model limit. Estimates are made for the ground state t and α spectroscopic factors. The 3.56 MeV M1 transition current density is calculated for both models and compared with experiment. (Auth.)
Longitudinal vector form factors in weak decays of nuclei
The longitudinal form factors of the weak vector current of particles with spin J = 1/2 and isospin I = 1/2 are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets
A note on connected formula for form factors
He, Song
2016-01-01
In this note we study the connected prescription, originally derived from Witten's twistor string theory, for tree-level form factors in ${\\cal N}=4$ super-Yang-Mills theory. The construction is based on the recently proposed four-dimensional scattering equations with $n$ massless on-shell states and one off-shell state, which we expect to work for form factors of general operators. To illustrate the universality of the prescription, we propose compact formulas for super form factors with chiral stress-tensor multiplet operator, and bosonic ones with scalar operators ${\\rm Tr}(\\phi^m)$ for arbitrary $m$.
Sudakov form factor in a massive vector field theory
The leading-logarithm approximation for the Sudakov form factor is examined in a theory containing massive fermion and massive neutral vector meson fields. In the on-shell case, where there is only one mass scale (the meson mass), the Sudakov form factor in this model agrees with the result in QED. In the off-shell case, however, with two different mass scales (the meson mass and the off-shell mass of the fermion), the Sudakov form factor differs from the QED result. copyright 1997 The American Physical Society
Roaming form factors for the tricritical to critical Ising flow
Horvath, D X; Takacs, G
2016-01-01
We study the massless flows described by the staircase model introduced by Al.B. Zamolodchikov through the analytic continuation of the sinh-Gordon S-matrix, focusing on the renormalisation group flow from the tricritical to the critical Ising model. We show that the properly defined roaming limits of certain sinh-Gordon form factors are identical to the form factors of the order and disorder operators for the massless flow. As a by-product, we also construct form factors for a semi-local field in the sinh-Gordon model, which can be associated with the twist field in the ultraviolet limiting free massless bosonic theory.
Roaming form factors for the tricritical to critical Ising flow
Horváth, D. X.; Dorey, P. E.; Takács, G.
2016-07-01
We study the massless flows described by the staircase model introduced by Al.B. Zamolodchikov through the analytic continuation of the sinh-Gordon S-matrix, focusing on the renormalisation group flow from the tricritical to the critical Ising model. We show that the properly defined roaming limits of certain sinh-Gordon form factors are identical to the form factors of the order and disorder operators for the massless flow. As a by-product, we also construct form factors for a semi-local field in the sinh-Gordon model, which can be associated with the twist field in the ultraviolet limiting free massless bosonic theory.
Longitudinal vector form factors in weak decays of nuclei
Simkovic, F; Krivoruchenko, M I
2015-01-01
The longitudinal form factors of the weak vector current of particles with spin $ J = 1/2 $ and isospin $ I = 1/2 $ are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets.
Longitudinal vector form factors in weak decays of nuclei
Šimkovic, F. [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); Department of Nuclear Physics and Biophysics, Comenius University, Mlynská dolina F1 SK–842 48 Bratislava (Slovakia); Kovalenko, S. [Universidad Técnica Federico Santa Mariya, Centro-Cientifico-Tecnológico de Valparaiso, Casilla 110-V, Valparaiso (Chile); Krivoruchenko, M. I. [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna (Russian Federation); Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow (Russian Federation)
2015-10-28
The longitudinal form factors of the weak vector current of particles with spin J = 1/2 and isospin I = 1/2 are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets.
Thermodynamics and form factors of supersymmetric integrable field theories
We study on-shell and off-shell properties of the supersymmetric Sinh-Gordon and perturbed SUSY Yang-Lee models using the thermodynamic Bethe ansatz and form factors. Identifying the supersymmetric models with the Eight Vertex Free Fermion Model, we derive the inversion relation for the inhomogeneous transfer matrix and TBA equations and get correct UV results. We obtain two-point form factors of the trace of energy-momentum tensor using the Watson equations and their SUSY transformations. As an application, we compute the UV central charge using these form factors and spectral representation of the C-theorem. (author). 49 refs, 1 fig., 1 tab
Dipion decays of heavy baryons
Compared with the charmed baryons, the bottom baryons are not known very well both experimentally and theoretically. In this paper, we investigate the dipion strong decays of the P-wave and D-wave excited bottom baryons in the framework of the QPC model. We also extend the same analysis to the charmed baryons
Torsten Leddig
2012-11-01
From inclusive measurements, it is known that about 7% of all mesons decay into final states with baryons. In these decays, some striking features become visible compared to mesonic decays. The largest branching fractions come with quite moderate multiplicities of 3–4 hadrons. We note that two-body decays to baryons are suppressed relative to three- and four-body decays. In most of these analyses, the invariant baryon–antibaryon mass shows an enhancement near the threshold. We propose a phenomenological interpretation of this quite common feature of hadronization to baryons.
Nucleon axial form factors from two-flavour Lattice QCD
Junnarkar, P M; Djukanovic, D; von Hippel, G; Hua, J; Jäger, B; Meyer, H B; Rae, T D; Wittig, H
2014-01-01
We present preliminary results on the axial form factor $G_A(Q^2)$ and the induced pseudoscalar form factor $G_P(Q^2)$ of the nucleon. A systematic analysis of the excited-state contributions to form factors is performed on the CLS ensemble `N6' with $m_\\pi = 340 \\ \\text{MeV}$ and lattice spacing $a \\sim 0.05 \\ \\text{fm}$. The relevant three-point functions were computed with source-sink separations ranging from $t_s \\sim 0.6 \\ \\text{fm}$ to $t_s \\sim \\ 1.4 \\ \\text{fm}$. We observe that the form factors suffer from non-trivial excited-state contributions at the source-sink separations available to us. It is noted that naive plateau fits underestimate the excited-state contributions and that the method of summed operator insertions correctly accounts for these effects.
The connected prescription for form factors in twistor space
Brandhuber, Andreas; Panerai, Rodolfo; Spence, Bill; Travaglini, Gabriele
2016-01-01
We propose a connected prescription formula in twistor space for all tree-level form factors of the stress tensor multiplet operator in $\\mathcal{N}=4$ super Yang-Mills, which is a generalisation of the expression of Roiban, Spradlin and Volovich for superamplitudes. By introducing link variables, we show that our formula is identical to the recently proposed four-dimensional scattering equations for form factors. Similarly to the case of amplitudes, the link representation of form factors is shown to be directly related to BCFW recursion relations, and is considerably more tractable than the scattering equations. We also discuss how our results are related to a recent Grassmannian formulation of form factors, and comment on a possible derivation of our formula from ambitwistor strings.
Form factors in magnetic scattering of thermal neutrons
Ballou, Rafik
2007-01-01
This lecture addresses the concept of form factor in magnetic scattering of thermal neutrons, analyzing its meaning, discussing its measurement by polarized neutrons and detailing its computation for the ions by the spherical tensor operator formalism.
Infrared photons and gluons and the electromagnetic quark form factor
A method for a consistent treatment of the infrared behaviour of QED and QCD is presented. As an application of the method the calculation of the electromagnetic quark form factor is discussed. (M.F.W.)
Hadronic Form Factors in Asymptotically Free Field Theories
Gross, D. J.; Treiman, S. B.
1974-01-01
The breakdown of Bjorken scaling in asymptotically free gauge theories of the strong interactions is explored for its implications on the large q{sup 2} behavior of nucleon form factors. Duality arguments of Bloom and Gilman suggest a connection between the form factors and the threshold properties of the deep inelastic structure functions. The latter are addressed directly in an analysis of asymptotically free theories; and through the duality connection we are then led to statements about the form factors. For very large q{sup 2} the form factors are predicted to fall faster than any inverse power of q{sup 2}. For the more modest range of q{sup 2} reached in existing experiments the agreement with data is fairly good, though this may well be fortuitous. Extrapolations beyond this range are presented.
Pion Form Factor in the NLC QCD SR approach
Bakulev, A P; Stefanis, N G
2009-01-01
We present results of a calculation of the electromagnetic pion form factor within a framework of QCD Sum Rules with nonlocal condensates and using a perturbative spectral density which includes \\mathcal{O}(\\alpha_s) contributions.
Proton Form Factors Measurements in the Time-Like Region
Anulli, F.; /Frascati
2007-10-22
I present an overview of the measurement of the proton form factors in the time-like region. BABAR has recently measured with great accuracy the e{sup +}e{sup -} {yields} p{bar p} reaction from production threshold up to an energy of {approx} 4.5 GeV, finding evidence for a ratio of the electric to magnetic form factor greater than unity, contrary to expectation. In agreement with previous measurements, BABAR confirmed the steep rise of the magnetic form factor close to the p{bar p} mass threshold, suggesting the possible presence of an under-threshold N{bar N} vector state. These and other open questions related to the nucleon form factors both in the time-like and space-like region, wait for more data with different experimental techniques to be possibly solved.
Classical limit of diagonal form factors and HHL correlators
Bajnok, Zoltan
2016-01-01
We propose an expression for the classical limit of diagonal form factors in which we integrate the corresponding observable over the moduli space of classical solutions. In infinite volume the integral has to be regularized by proper subtractions and we present the one, which corresponds to the classical limit of the connected diagonal form factors. In finite volume the integral is finite and can be expressed in terms of the classical infinite volume diagonal form factors and subvolumes of the moduli space. We analyze carefully the periodicity properties of the finite volume moduli space and found a classical analogue of the Bethe-Yang equations. By applying the results to the heavy-heavy-light three point functions we can express their strong coupling limit in terms of the classical limit of the sine-Gordon diagonal form factors.
Rare $B$ decays using lattice QCD form factors
Horgan, R R; Meinel, S; Wingate, M
2015-01-01
In this write-up we review and update our recent lattice QCD calculation of $B \\to K^*$, $B_s \\to \\phi$, and $B_s \\to K^*$ form factors [arXiv:1310.3722]. These unquenched calculations, performed in the low-recoil kinematic regime, provide a significant improvement over the use of extrapolated light cone sum rule results. The fits presented here include further kinematic constraints and estimates of additional correlations between the different form factor shape parameters. We use these form factors along with Standard Model determinations of Wilson coefficients to give Standard Model predictions for several observables [arXiv:1310.3887]. The modest improvements to the form factor fits lead to improved determinations of $F_L$, the fraction of longitudinally polarized vector mesons, but have little effect on most other observables.
Lattice results on the meson electric form factor
A calculation is outlined and results presented for the electric form factor, measured at two values of the momentum, of the pseudo-Goldstone meson within the staggered formulation of lattice fermions
Normalization Of Thermal-Radiation Form-Factor Matrix
Tsuyuki, Glenn T.
1994-01-01
Report describes algorithm that adjusts form-factor matrix in TRASYS computer program, which calculates intraspacecraft radiative interchange among various surfaces and environmental heat loading from sources such as sun.
Breather boundary form factors in sine-Gordon theory
A previously conjectured set of exact form factors of boundary exponential operators in the sinh-Gordon model is tested against numerical results from boundary truncated conformal space approach in boundary sine-Gordon theory, related by analytic continuation to sinh-Gordon model. We find that the numerical data strongly support the validity of the form factors themselves; however, we also report a discrepancy in the case of diagonal matrix elements, which remains unresolved for the time being.
Charm and bottom hadronic form factors with QCD sum rules
We present a brief review of some calculations of form factors and coupling constants in vertices with charm and bottom mesons in the framework of QCD sum rules. We first discuss the motivation for this work, describing possible applications of these form factors to charm and bottom decays processes. We first make a summarize of the QCD sum rules method. We give special attention to the uncertainties of the method introducing by the intrinsic variation of the parameters. Finally we conclude.
In-medium modified energy-momentum tensor form factors
Jung, Ju-Hyun; Yakhshiev, Ulugbek; Kim, Hyun-Chul
2014-04-01
In this talk, we report a recent investigation on the energy-momentum tensor form factors of the nucleon in nuclear medium, based on the framework of the in-medium modified chiral soliton model. The model was constructed by taking into account the influence of the surrounding environment to the mesonic sector (π-, ρ- and ω-meson properties). We briefly discuss the results of the energy-momentum tensor form factors.
In-medium modified energy-momentum tensor form factors
In this talk, we report a recent investigation on the energy-momentum tensor form factors of the nucleon in nuclear medium, based on the framework of the in-medium modified chiral soliton model. The model was constructed by taking into account the influence of the surrounding environment to the mesonic sector (π-, ρ- and ω-meson properties). We briefly discuss the results of the energy-momentum tensor form factors. (author)
Nucleon tensor form factors in a relativistic confined quark model
Gutsche, Thomas; Korner, Jurgen G; Kovalenko, Sergey; Lyubovitskij, Valery E
2016-01-01
We present results for the isotriplet and isosinglet tensor form factors of the nucleon in the relativistic confined quark model. The model allows us to calculate not only their normalizations at $Q^2=0$ and the related tensor charges, but also the full $Q^2$-dependence. Our results are compared to existing data and predictions of other theoretical approaches. We stress the importance of these form factors for the phenomenology of physics beyond the Standard Model.
Transport coefficients of heavy baryons
Tolos, Laura; Torres-Rincon, Juan M.; Das, Santosh K.
2016-08-01
We compute the transport coefficients (drag and momentum diffusion) of the low-lying heavy baryons Λc and Λb in a medium of light mesons formed at the later stages of high-energy heavy-ion collisions. We employ the Fokker-Planck approach to obtain the transport coefficients from unitarized baryon-meson interactions based on effective field theories that respect chiral and heavy-quark symmetries. We provide the transport coefficients as a function of temperature and heavy-baryon momentum, and analyze the applicability of certain nonrelativistic estimates. Moreover we compare our outcome for the spatial diffusion coefficient to the one coming from the solution of the Boltzmann-Uehling-Uhlenbeck transport equation, and we find a very good agreement between both calculations. The transport coefficients for Λc and Λb in a thermal bath will be used in a subsequent publication as input in a Langevin evolution code for the generation and propagation of heavy particles in heavy-ion collisions at LHC and RHIC energies.
Chiral dynamics of baryons in the perturbative chiral quark model
Pumsa-ard, K.
2006-07-01
In this work we develop and apply variants of a perturbative chiral quark model (PCQM) to the study of baryonic properties dominantly in the low-energy region. In a first step we consider a noncovariant form of the PCQM, where confinement is modelled by a static, effective potential and chiral corrections are treated to second order, in line with similar chiral quark models. We apply the PCQM to the study of the electromagnetic form factors of the baryon octet. We focus in particular on the low-energy observables such as the magnetic moments, the charge and magnetic radii. In addition, the electromagnetic N-delta transition is also studied in the framework of the PCQM. In the chiral loop calculations we consider a quark propagator, which is restricted to the quark ground state, or in hadronic language to nucleon and delta intermediate states, for simplicity. We furthermore include the low-lying excited states to the quark propagator. In particular, the charge radius of the neutron and the transverse helicity amplitudes of the N-delta transition are considerably improved by this additional effect. In a next step we develop a manifestly Lorentz covariant version of the PCQM, where in addition higher order chiral corrections are included. The full chiral quark Lagrangian is motivated by and in analogy to the one of Chiral Perturbation Theory (ChPT). This Lagrangian contains a set of low energy constants (LECs), which are parameters encoding short distance effects and heavy degrees of freedom. We evaluate the chiral Lagrangian to order O(p{sup 4}) and to one loop to generate the dressing of the bare quark operators by pseudoscalar mesons. In addition we include the vector meson degrees of freedom in our study. Projection of the dressed quark operators on the baryonic level serves to calculate the relevant matrix elements. In a first application of this scheme, we resort to a parameterization of the valence quark form factors in the electromagnetic sector. Constraints
Photoproduction of hermaphrodite baryons
We show that photoexcitation of the lightest hermaphrodite baryons is strongly suppressed from proton targets but allowed from neutrons, a result that is reminiscent of a quark model selection rule due to Moorhouse. This is consistent with suggestions that the P11 (1710) is the lightest q3G baryon and eliminates the possibility of considerable mixing of q3G into the nucleon and delta's Fock space wavefunctions. (orig.)
Lifetime and production rate of beauty baryons from Z decays
Abreu, P; Adye, T; Agasi, E; Ajinenko, I; Aleksan, Roy; Alekseev, G D; Allport, P P; Almehed, S; Alvsvaag, S J; Amaldi, Ugo; Amato, S; Andreazza, A; Andrieux, M L; Antilogus, P; Apel, W D; Arnoud, Y; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Bambade, P; Barão, F; Barate, R; Barbiellini, Guido; Bardin, Dimitri Yuri; Barker, G J; Baroncelli, A; Bärring, O; Barrio, J A; Bartl, Walter; Bates, M J; Battaglia, Marco; Baubillier, M; Baudot, J; Becks, K H; Begalli, M; Beillière, P; Belokopytov, Yu A; Benvenuti, Alberto C; Berggren, M; Bertrand, D; Bianchi, F; Bigi, M; Bilenky, S M; Billoir, P; Bloch, D; Blume, M; Blyth, S; Bocci, V; Bolognese, T; Bonesini, M; Bonivento, W; Booth, P S L; Borisov, G; Bosio, C; Bosworth, S; Botner, O; Bouquet, B; Bourdarios, C; Bowcock, T J V; Bozzo, M; Branchini, P; Brand, K D; Brenner, R A; Bricman, C; Brillault, L; Brown, R C A; Brückman, P; Brunet, J M; Bugge, L; Buran, T; Buys, A; Caccia, M; Calvi, M; Camacho-Rozas, A J; Camporesi, T; Canale, V; Canepa, M; Cankocak, K; Cao, F; Carena, F; Carrilho, P; Carroll, L; Caso, Carlo; Castillo-Gimenez, M V; Cattai, A; Cavallo, F R; Cerrito, L; Chabaud, V; Chapkin, M M; Charpentier, P; Chaussard, L; Chauveau, J; Checchia, P; Chelkov, G A; Chierici, R; Chliapnikov, P V; Chochula, P; Chorowicz, V; Cindro, V; Collins, P; Contreras, J L; Contri, R; Cortina, E; Cosme, G; Cossutti, F; Crawley, H B; Crennell, D J; Crosetti, G; Cuevas-Maestro, J; Czellar, S; Dahl-Jensen, Erik; Dahm, J; D'Almagne, B; Dam, M; Damgaard, G; Daum, A; Dauncey, P D; Davenport, Martyn; Da Silva, W; Defoix, C; Della Ricca, G; Delpierre, P A; Demaria, N; De Angelis, A; De Boeck, H; de Boer, Wim; De Brabandere, S; De Clercq, C; La Vaissière, C de; De Lotto, B; De Min, A; De Paula, L S; De Saint-Jean, C; Dijkstra, H; Di Ciaccio, Lucia; Djama, F; Dolbeau, J; Dönszelmann, M; Doroba, K; Dracos, M; Drees, J; Drees, K A; Dris, M; Dufour, Y; Dupont, F; Edsall, D M; Ehret, R; Eigen, G; Ekelöf, T J C; Ekspong, Gösta; Elsing, M; Engel, J P; Ershaidat, N; Erzen, B; Espirito-Santo, M C; Falk, E; Fassouliotis, D; Feindt, Michael; Fenyuk, A; Ferrer, A; Filippas-Tassos, A; Firestone, A; Föth, H; Fokitis, E; Fontanelli, F; Formenti, F; Franek, B J; Frenkiel, P; Fries, D E C; Frodesen, A G; Frühwirth, R; Fulda-Quenzer, F; Fürstenau, H; Fuster, J A; Galloni, A; Gamba, D; Gandelman, M; García, C; García, J; Gaspar, C; Gasparini, U; Gavillet, P; Gazis, E N; Gelé, D; Gerber, J P; Gibbs, M; Gillespie, D; Gokieli, R; Golob, B; Gopal, Gian P; Gorn, L; Górski, M; Gracco, Valerio; Graziani, E; Grosdidier, G; Gunnarsson, P; Günther, M; Guy, J; Haedinger, U; Hahn, F; Hahn, M; Hahn, S; Hajduk, Z; Hallgren, A; Hamacher, K; Hao, W; Harris, F J; Hedberg, V; Henriques, R P; Hernández, J J; Herquet, P; Herr, H; Hessing, T L; Higón, E; Hilke, Hans Jürgen; Hill, T S; Holmgren, S O; Holt, P J; Holthuizen, D J; Houlden, M A; Hrubec, Josef; Huet, K; Hultqvist, K; Ioannou, P; Jackson, J N; Jacobsson, R; Jalocha, P; Janik, R; Jarlskog, G; Jarry, P; Jean-Marie, B; Johansson, E K; Jönsson, L B; Jönsson, P E; Joram, Christian; Juillot, P; Kaiser, M; Kalmus, George Ernest; Kapusta, F; Karlsson, M; Karvelas, E; Katsanevas, S; Katsoufis, E C; Keränen, R; Khomenko, B A; Khovanskii, N N; King, B J; Kjaer, N J; Klein, H; Klovning, A; Kluit, P M; Köhne, J H; Köne, B; Kokkinias, P; Koratzinos, M; Kostyukhin, V; Kourkoumelis, C; Kuznetsov, O; Kramer, P H; Krammer, Manfred; Kreuter, C; Królikowski, J; Kronkvist, I J; Krumshtein, Z; Krupinski, W; Kubinec, P; Kucewicz, W; Kurvinen, K L; Lacasta, C; Laktineh, I; Lamblot, S; Lamsa, J; Lanceri, L; Lane, D W; Langefeld, P; Lapin, V; Last, I; Laugier, J P; Lauhakangas, R; Leder, Gerhard; Ledroit, F; Lefébure, V; Legan, C K; Leitner, R; Lemoigne, Y; Lemonne, J; Lenzen, Georg; Lepeltier, V; Lesiak, T; Liko, D; Lindner, R; Lipniacka, A; Lippi, I; Lörstad, B; Lokajícek, M; Loken, J G; López, J M; López-Fernandez, A; López-Aguera, M A; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J N; Maehlum, G; Maio, A; Malychev, V; Mandl, F; Marco, J; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Maron, T; Martínez-Rivero, C; Martínez-Vidal, F; Martí i García, S; Matorras, F; Matteuzzi, C; Matthiae, Giorgio; Mazzucato, M; McCubbin, M L; McKay, M; McNulty, M; Medbo, J; Meroni, C; Meyer, W T; Michelotto, M; Migliore, E; Mirabito, L; Mitaroff, Winfried A; Mjörnmark, U; Moa, T; Møller, R; Mönig, K; Monge, M R; Morettini, P; Müller, H; Mundim, L M; Murray, W J; Muryn, B; Myatt, Gerald; Naraghi, F; Navarria, Francesco Luigi; Navas, S; Negri, P; Némécek, S; Neumann, W; Neumeister, N; Nicolaidou, R; Nielsen, B S; Nieuwenhuizen, M; Nikolaenko, V; Niss, P; Nomerotski, A; Normand, Ainsley; Oberschulte-Beckmann, W; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Ostankov, A P; Österberg, K; Ouraou, A; Paganini, P; Paganoni, M; Pagès, P; Palka, H; Papadopoulou, T D; Pape, L; Parkes, C; Parodi, F; Passeri, A; Pegoraro, M; Peralta, L; Pernegger, H; Pernicka, Manfred; Perrotta, A; Petridou, C; Petrolini, A; Phillips, H T; Piana, G; Pierre, F; Plaszczynski, S; Podobrin, O; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Prest, M; Privitera, P; Pukhaeva, N; Pullia, Antonio; Radojicic, D; Ragazzi, S; Rahmani, H; Rames, J; Ratoff, P N; Read, A L; Reale, M; Rebecchi, P; Redaelli, N G; Reid, D; Renton, P B; Resvanis, L K; Richard, F; Richardson, J; Rídky, J; Rinaudo, G; Ripp, I; Romero, A; Roncagliolo, I; Ronchese, P; Roos, L; Rosenberg, E I; Rosso, E; Roudeau, Patrick; Rovelli, T; Rückstuhl, W; Ruhlmann-Kleider, V; Ruiz, A; Rybicki, K; Saarikko, H; Sacquin, Yu; Sadovskii, A; Sajot, G; Salt, J; Sánchez, J; Sannino, M; Schneider, H; Schyns, M A E; Sciolla, G; Scuri, F; Sedykh, Yu; Segar, A M; Seitz, A; Sekulin, R L; Shellard, R C; Siccama, I; Siegrist, P; Simonetti, S; Simonetto, F; Sissakian, A N; Sitár, B; Skaali, T B; Smadja, G; Smirnov, N; Smirnova, O G; Smith, G R; Sosnowski, R; Souza-Santos, D; Spassoff, Tz; Spiriti, E; Squarcia, S; Stäck, H; Stanescu, C; Stapnes, Steinar; Stavitski, I; Stepaniak, K; Stichelbaut, F; Stocchi, A; Strauss, J; Strub, R; Stugu, B; Szczekowski, M; Szeptycka, M; Tabarelli de Fatis, T; Tavernet, J P; Chikilev, O G; Tilquin, A; Timmermans, J; Tkatchev, L G; Todorov, T; Toet, D Z; Tomaradze, A G; Tomé, B; Torassa, E; Tortora, L; Tranströmer, G; Treille, D; Trischuk, W; Tristram, G; Trombini, A; Troncon, C; Tsirou, A L; Turluer, M L; Tyapkin, I A; Tyndel, M; Tzamarias, S; Überschär, B; Überschär, S; Ullaland, O; Uvarov, V; Valenti, G; Vallazza, E; van Apeldoorn, G W; van Dam, P; Van Doninck, W K; Van Eldik, J; Vassilopoulos, N; Vegni, G; Ventura, L; Venus, W A; Verbeure, F; Verlato, M; Vertogradov, L S; Vilanova, D; Vincent, P; Vitale, L; Vlasov, E; Vodopyanov, A S; Vrba, V; Wahlen, H; Walck, C; Wehr, A; Weierstall, M; Weilhammer, Peter; Wetherell, Alan M; Wicke, D; Wickens, J H; Wielers, M; Wilkinson, G R; Williams, W S C; Winter, M; Witek, M; Wormser, G; Woschnagg, K; Yip, K; Zach, F; Zacharatou-Jarlskog, C; Zaitsev, A; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zevgolatakos, E; Zimin, N I; Zito, M; Zontar, D; Zuberi, R; Zucchelli, G C; Zumerle, G
1995-01-01
The production and decay of beauty baryons (b-baryons) have been studied using 1.7 \\times 10^6 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a \\Lambda and a lepton to tag the b-baryon decay. The second method associated fully reconstructed \\Lambda_c baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured: \\begin{eqnarray*} f(\\qb \\ra \\Bb) \\times \\BR(\\Bb \\ra \\mLs \\ell\\bar{\
Bertini, D. [Lyon-1 Univ., 69 (France)
1997-04-24
By using the data accumulated in the DELPHI experiment from 1992 to 1994 we present the results of the production rate measurement of {Lambda}{sub c} charmed baryons generated in the bb-bar and cc-bar events. For these measurements we reconstructed entirely the {Lambda}{sub c} baryons decaying in pK{pi}. Then we select a set of bottom baryons {Lambda}{sub b}{sup 0} by means of its semi-leptonic decays in {Lambda}{sub c}{sup +}l{sup -}{nu}{sub l}-bar. The study of distribution of these events as a function of the transfer momentum allowed estimating for the first time the slope of the {Lambda}{sub b}{sup 0} form factor. (author) 93 refs.
Online Soil Science Lesson 3: Soil Forming Factors
This lesson explores the five major factors of soil formation, namely: 1) climate; 2) organisms; 3) time; 4) topography; and 5) parent material and their influence in forming soil. The distinction between active and passive factors, moisture and temperature regimes, organism and topographic influen...
Ramalho, G; Weil, J; van Hees, H; Mosel, U
2015-01-01
The $\\Delta(1232) \\to \\gamma^\\ast N$ magnetic dipole form factor ($G_M^\\ast$) is described here within a new covariant model that combines the valence quark core together with the pion cloud contributions. The pion cloud term is parameterized by two terms: one connected to the pion electromagnetic form factor, the other to the photon interaction with intermediate baryon states. The model can be used in studies of pp and heavy ion collisions. In the timelike region this new model improves the results obtained with a constant form factor model fixed at its value at zero momentum transfer. At the same time, and in contrast to the Iachello model, this new model predicts a peak for the transition form factor at the expected position, i.e. at the $\\rho$ mass pole. We calculate the decay of the $\\Delta \\to \\gamma N$ transition, the Dalitz decay ($\\Delta \\to e^+ e^- N$), and the $\\Delta$ mass distribution function. The impact of the model on dilepton spectra in pp collisions is also discussed.
On a four-loop form factor in N=4
Boels, Rutger H; Yang, Gang
2016-01-01
We report on progress toward computing a four-loop supersymmetric form factor in maximally supersymmetric Yang-Mills theory. A representative example particle content from the involved supermultiplets is a stress-tensor operator with two on-shell gluons. In previous work, the integrand for this form factor was obtained using color-kinematic duality in a particularly simple form. Here the result of applying integration-by-parts identities is discussed and cross-checks of the result is performed. Rational IBP relations and their reduction are introduced as a potentially useful aide.
Nucleon form factors, generalized parton distributions and quark angular momentum
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale μ=2 GeV to be Juv=0.230+0.009-0.024 and Jdv=-0.004+0.010-0.016.
Knippschild, Bastian
2012-03-05
Quantum Chromodynamics (QCD) is the theory of strong interactions, one of the four fundamental forces in our Universe. It describes the interaction of gluons and quarks which build up hadrons like protons and neutrons. Most of the visible matter in our universe is made of protons and neutrons. Hence, we are interested in their fundamental properties like their masses, their distribution of charge and their shape. The only known theoretical, non-perturbative and ab initio method to investigate hadron properties at low energies is lattice Quantum Chromodynamics (lattice QCD). However, up-to-date simulations (especially for baryonic quantities) do not achieve the accuracy of experiments. In fact, current simulations do not even reproduce the experimental values for the form factors. The question arises wether these deviations can be explained by systematic effects in lattice QCD simulations. This thesis is about the computation of nucleon form factors and other hadronic quantities from lattice QCD. So called Wilson fermions are used and the u- and d-quarks are treated fully dynamically. The simulations were performed using gauge ensembles with a range of lattice spacings, volumes and pion masses. First of all, the lattice spacing was set to be able to make contact between the lattice results and their experimental complement and to be able to perform a continuum extrapolation. The light quark mass has been computed and found to be m{sub ud}{sup MS}(2 GeV)=3.03(17)(38) MeV. This value is in good agreement with values from experiments and other lattice determinations. Electro-magnetic and axial form factors of the nucleon have been calculated. From these form factors the nucleon radii and the coupling constants were computed. The different ensembles enabled us to investigate systematically the dependence of these quantities on the volume, the lattice spacing and the pion mass. Finally we perform a continuum extrapolation and chiral extrapolations to the physical point
Study of ψ(3770) decaying to baryon anti-baryon pairs
Xia, Li-Gang
2016-05-01
To study the decays of ψ (3770) going to baryon anti-baryon pairs (B B bar), all available experiments of measuring the cross sections of e+e- → B B bar at center-of-mass energy ranging from 3.0 GeV to 3.9 GeV are combined. To relate the baryon octets, a model based on the SU(3) flavor symmetry is used and the SU(3) breaking effects are also considered. Assuming the electric and magnetic form factors are equal (|GE | = |GM |), a global fit including the interference between the QED process and the resonant process is performed. The branching fraction of ψ (3770) → B B bar is determined to be (2.4 ± 0.8 ± 0.3) ×10-5, (1.7 ± 0.6 ± 0.1) ×10-5, (4.5 ± 0.9 ± 0.1) ×10-5, (4.5 ± 0.9 ± 0.1) ×10-5, (2.0 ± 0.7 ± 0.1) ×10-5, and (2.0 ± 0.7 ± 0.1) ×10-5 for B = p , Λ ,Σ+ ,Σ0 ,Ξ- and Ξ0, respectively, where the first uncertainty is from the global fit and the second uncertainty is the systematic uncertainty due to the assumption |GE | = |GM |. They are at least one order of magnitude larger than a simple scaling of the branching fraction of J / ψ / ψ (3686) → B B bar .
Study of ψ(3770 decaying to baryon anti-baryon pairs
Li-Gang Xia
2016-05-01
Full Text Available To study the decays of ψ(3770 going to baryon anti-baryon pairs (BB¯, all available experiments of measuring the cross sections of e+e−→BB¯ at center-of-mass energy ranging from 3.0 GeV to 3.9 GeV are combined. To relate the baryon octets, a model based on the SU(3 flavor symmetry is used and the SU(3 breaking effects are also considered. Assuming the electric and magnetic form factors are equal (|GE|=|GM|, a global fit including the interference between the QED process and the resonant process is performed. The branching fraction of ψ(3770→BB¯ is determined to be (2.4±0.8±0.3×10−5, (1.7±0.6±0.1×10−5, (4.5±0.9±0.1×10−5, (4.5±0.9±0.1×10−5, (2.0±0.7±0.1×10−5, and (2.0±0.7±0.1×10−5 for B=p,Λ,Σ+,Σ0,Ξ− and Ξ0, respectively, where the first uncertainty is from the global fit and the second uncertainty is the systematic uncertainty due to the assumption |GE|=|GM|. They are at least one order of magnitude larger than a simple scaling of the branching fraction of J/ψ/ψ(3686→BB¯.
Dispersion-theoretical analysis of the nucleon electromagnetic form factors
The structure of the proton and the neutron is of fundamental importance for the study of the strong interaction dynamics over a wide range of momentum transfers. The nucleon form factors encode information on the internal structure of the nucleon as probed by the electromagnetic interaction, and, to a certain extent, reflect the charge and magnetisation distributions within the proton and the neutron. In this thesis we report on our investigation of the electromagnetic form factors of the proton and the neutron with dispersion relation techniques, including known experimental input on the ππ, K anti K and the ρπ continua and perturbative QCD constraints. We include new experimental data on the pion form factor and the nucleon form factors in our simultaneous analysis of all four form factors in both the space- and the timelike regions for all momentum transfers, and perform Monte- Carlo sampling in order to obtain theoretical uncertainty bands. Finally, we discuss the implications of our results on the pion cloud of the nucleon, the nucleon radii and the Okubo-Zweig-Iizuka rule, and present our results of a model-independent approach to estimating two-photon effects in elastic electron-proton scattering. (orig.)
Transition Form Factors: A Unique Opportunity to Connect Non-Perturbative Strong Interactions to QCD
Gothe, Ralf W. [University of South Carolina, Columbia, SC (United States)
2014-01-01
Meson-photoproduction measurements and their reaction-amplitude analyses can establish more sensitively, and in some cases in an almost model-independent way, nucleon excitations and non-resonant reaction amplitudes. However, to investigate the strong interaction from explored — where meson-cloud degrees of freedom contribute substantially to the baryon structure — to still unexplored distance scales — where quark degrees of freedom dominate and the transition from dressed to current quarks occurs — we depend on experiments that allow us to measure observables that are probing this evolving non-perturbative QCD regime over its full range. Elastic and transition form factors are uniquely suited to trace this evolution by measuring elastic electron scattering and exclusive single-meson and double-pion electroproduction cross sections off the nucleon. These exclusive measurements will be extended to higher momentum transfers with the energy-upgraded CEBAF beam at JLab to study the quark degrees of freedom, where their strong interaction is responsible for the ground and excited nucleon state formations. After establishing unprecedented high-precision data, the imminent next challenge is a high-quality analysis to extract these relevant electrocoupling parameters for various resonances that then can be compared to state-of-the-art models and QCD-based calculations. Recent results will demonstrate the status of the analysis and of their theoretical descriptions, and an experimental and theoretical outlook will highlight what shall and may be achieved in the new era of the 12-GeV upgraded transition form factor program.
SU(4) breaking for semileptonic decays of charmed baryons
Buccella, F.; Sciarrino, A.; Sorba, P.
1978-08-01
The effects of SU(4) breaking are studied in connection with the semileptonic decays and magnetic moments of the baryons with charm + 1. Substantial suppression factors are predicted for the decay in which the final baryon belongs to the decimet. The consequences of a vanishing magnetic moment for the charmed quark are studied in detail.
SU(4) breaking for semileptonic decays of charmed baryons
The effects of SU(4) breaking are studied in connection with the semileptonic decays and magnetic moments of the baryons with charm + 1. Substantial suppression factors are predicted for the decay in which the final baryon belongs to the decimet. The consequences of a vanishing magnetic moment for the charmed quark are studied in detail
Zero modes method and form factors in quantum integrable models
S. Pakuliak
2015-04-01
Full Text Available We study integrable models solvable by the nested algebraic Bethe ansatz and possessing GL(3-invariant R-matrix. Assuming that the monodromy matrix of the model can be expanded into series with respect to the inverse spectral parameter, we define zero modes of the monodromy matrix entries as the first nontrivial coefficients of this series. Using these zero modes we establish new relations between form factors of the elements of the monodromy matrix. We prove that all of them can be obtained from the form factor of a diagonal matrix element in special limits of Bethe parameters. As a result we obtain determinant representations for form factors of all the entries of the monodromy matrix.
Form factor ratio from unpolarized elastic electron proton scattering
Pacetti, Simone
2016-01-01
A reanalysis of unpolarized electron-proton elastic scattering data is done in terms of the electric to magnetic form factor squared ratio, $R^2$. The present analysis shows that $R^2$ is a useful quantity that contains reliable and coherent information. This ratio is in principle more robust against the experimental corrections. The comparison with the ratio extracted from the measurement of the longitudinal to transverse polarization of the recoil proton in polarized electron-proton scattering shows that the results are indeed compatible within the experimental errors. Limits are set on the kinematics where the physical information on the form factors can be safely extracted. The results presented in this work bring a decisive piece of information in the controversy on the deviation of the proton electromagnetic form factors from the dipole dependence.
Computation of 3D form factors in complex environments
The calculation of radiant interchange among opaque surfaces in a complex environment poses the general problem of determining the visible and hidden parts of the environment. In many thermal engineering applications, surfaces are separated by radiatively non-participating media and may be idealized as diffuse emitters and reflectors. Consenquently the net radiant energy fluxes are intimately related to purely geometrical quantities called form factors, that take into account hidden parts: the problem is reduced to the form factor evaluation. This paper presents the method developed for the computation of 3D form factors in the finite-element module of the system TRIO, which is a general computer code for thermal and fluid flow analysis. The method is derived from an algorithm devised for synthetic image generation. A comparison is performed with the standard contour integration method also implemented and suited to convex geometries. Several illustrative examples of finite-element thermal calculations in radiating enclosures are given
Time-like form factors of the nucleon
The electromagnetic form factors are an important tool to explore the structure of the nucleon. The extraction of space-like form factors from electron-proton scattering shows a discrepancy between data of unpolarized Rosenbluth measurements and of polarization experiments. This difference can be explained by means of two-photon exchange corrections. In the time-like region no comparable calculations have been done up to now for the corresponding processes. We investigate the influence of two-photon exchange in the reaction anti pp → e+e- with regard to determination of the time-like form factors and present calculations for future experiments at the PANDA rate at FAIR project.
Two-body form factors at high Q2
The charge form factor of a scalar deuteron at high momentum transfer is examined in a model employing scalar nucleons and mesons. With an eye toward establishing consistency criteria for more realistic calculations, several aspects of the model are examined in detail: the role of nucleon and meson singularities in the one-loop impulse diagram, the role of positive-and negative-energy nucleons, and the relationship to time-ordered perturbation theory. It is found that at large Q2 (1) the form factor is dominated by a term in which the spectator nucleon is on the mass shell, and (2) the meson singularity structure of the d-n-p vertex function is unimportant in determining the overall high-Q2 behaviour of the form factor
Sensitivity of the deuteron form factor to nucleon resonances
Herbst, K A; Herbst, Kelly Ann; Gross, Franz
1997-01-01
The sensitivity of the deuteron form factor to contributions from the excited states of the nucleon is explored using a simple model of the nucleon-nucleon interaction which employs a tower of charged nucleon resonances. The model is manifestly covariant, analytically solvable, and gauge invariant. The consequences of this model are studied in the simplest possible framework. We assume that all particles have spin zero and that the tower has only three charged members, which consist of the proton, the Roper, and a higher state in the vicinity of the $D_{13}$. Nucleon-nucleon S-wave phase shifts and the deuteron form factor are calculated using this three member tower, and the results are compared to similar calculations using the proton ground state only. We conclude that the deuteron form factor is insensitive to the presence of excited states of the proton unless those states are of sufficiently low mass to produce strong inelasticities in $NN$ scattering channels.
New empirical fits to the proton electromagnetic form factors
Recent measurements of the ratio of the elastic electromagnetic form factors of the proton, GEp/GMp, using the polarization transfer technique at Jefferson Lab show that this ratio decreases dramatically with increasing Q2, in contradiction to previous measurements using the Rosenbluth separation technique. Using this new high quality data as a constraint, we have reanalyzed most of the world e-p elastic cross section data. In this paper, we present a new empirical fit to the reanalyzed data for the proton elastic magnetic form factor in the region 0 2 2. As well, we present an empirical fit to the proton electromagnetic form factor ratio, GEp/GMp, which is valid in the region 0.1 2 2
Kaon semileptonic decay form factors with HISQ valence quarks
Gamiz, E; Bazavov, A; Bernard, C; Bouchard, C; DeTar, C; Du, D; El-Khadra, A X; Foley, J; Freeland, E D; Gottlieb, Steven; Heller, U M; Kim, J; Kronfeld, A S; Laiho, J; Levkova, L; Mackenzie, P B; Neil, E T; Oktay, M B; Qiu, Si-Wei; Simone, J N; Sugar, R; Toussaint, D; Van de Water, R S; Zhou, R
2012-01-01
We report on the status of our kaon semileptonic form factor calculations using the highly-improved staggered quark (HISQ) formulation to simulate the valence fermions. We present results for the form factor f_+^{K \\pi}(0) on the asqtad N_f=2+1 MILC configurations, discuss the chiral-continuum extrapolation, and give a preliminary estimate of the total error. We also present a more preliminary set of results for the same form factor but with the sea quarks also simulated with the HISQ action; these results include data at the physical light quark masses. The improvements that we expect to achieve with the use of the HISQ configurations and simulations at the physical quark masses are briefly discussed.
The Proton Form Factor Ratio Measurements at Jefferson Lab
Punjabi, Vina A. [Norfolk State University, Norfolk, VA (United States); Perdrisat, Charles F. [William and Mary College, Williamsburg, VA (United States)
2014-03-01
The ratio of the proton form factors, G{sub Ep}/G{sub Mp}, has been measured from Q{sup 2} of 0.5 GeV{sup 2} to 8.5 GeV{sup 2}, at the Jefferson Laboratory, using the polarization transfer method. This ratio is extracted directly from the measured ratio of the transverse and longitudinal polarization components of the recoiling proton in elastic electron-proton scattering. The discovery that the proton form factor ratio measured in these experiments decreases approximately linearly with four-momentum transfer, Q{sup 2}, for values above ~1 GeV{sup 2}, is one of the most significant results to come out of JLab. These results have had a large impact on progress in hadronic physics; and have required a significant rethinking of nucleon structure. The increasingly common use of the double-polarization technique to measure the nucleon form factors, in the last 15 years, has resulted in a dramatic improvement of the quality of all four nucleon electromagnetic form factors, G{sub Ep}, G{sub Mp}, G{sub En} and G{sub Mn}. There is an approved experiment at JLab, GEP(V), to continue the ratio measurements to 12 GeV{sup 2}. A dedicated experimental setup, the Super Bigbite Spectrometer (SBS), will be built for this purpose. It will be equipped with a focal plane polarimeter to measure the polarization of the recoil protons. The scattered electrons will be detected in an electromagnetic calorimeter. In this presentation, I will review the status of the proton elastic electromagnetic form factors and discuss a number of theoretical approaches to describe nucleon form factors.
Factorization, resummation and sum rules for heavy-to-light form factors
Wang, Yu-Ming
2016-01-01
Precision calculations of heavy-to-light form factors are essential to sharpen our understanding towards the strong interaction dynamics of the heavy-quark system and to shed light on a coherent solution of flavor anomalies. We briefly review factorization properties of heavy-to-light form factors in the framework of QCD factorization in the heavy quark limit and discuss the recent progress on the QCD calculation of $B \\to \\pi$ form factors from the light-cone sum rules with the $B$-meson distribution amplitudes. Demonstration of QCD factorization for the vacuum-to-$B$-meson correlation function used in the sum-rule construction and resummation of large logarithms in the short-distance functions entering the factorization theorem are presented in detail. Phenomenological implications of the newly derived sum rules for $B \\to \\pi$ form factors are further addressed with a particular attention to the extraction of the CKM matrix element $|V_{ub}|$.
Sudakov effects in B -> pi l nu form factors
Descotes, S
2002-01-01
In order to obtain information about the Standard Model from exclusive hadronic two-body B-decays, we have to quantify non-perturbative QCD effects. Approaches based on the factorization of mass singularities into hadronic distribution amplitudes and form factors provide a rigorous theoretical framework for the evaluation of these effects in the heavy quark limit. But it is not possible to calculate power corrections in a model-independent way, because of non-factorizing long-distance contributions. It has been argued that Sudakov effects suppress these contributions and render the corresponding corrections perturbatively calculable. In this paper we examine this claim for the related example of semileptonic B -> pi decays and conclude that it is not justified. The uncertainties in our knowledge of the mesons' distribution amplitudes imply that the calculations of the form factors are not sufficiently precise to be useful phenomenologically. Moreover, a significant contribution comes from the non-perturbative...
Master integrals for the four-loop Sudakov form factor
Rutger H. Boels
2016-01-01
Full Text Available The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N=4 supersymmetric Yang–Mills theory (SYM in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. The simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was largely obtained in integrand form in a previous work for N=4 SYM, up to a free parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP identities using a modified version of Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. Moreover, two of the integral topologies vanish after reduction. The appearing master integrals are cross-checked using independent algebraic-geometry techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Discrepancies between explicitly solving the IBP relations and the MINT approach are highlighted. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N=4 SYM and beyond are identified.
Master integrals for the four-loop Sudakov form factor
The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N=4) supersymmetric Yang-Mills theory (SYM) in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. Probably the simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was obtained in integrand form in a previous work for N=4 SYM, up to a single parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP) identities using (a tweaked version of) Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. The appearing master integrals are cross-checked using algebraic techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N=4 SYM and beyond are identified.
Master integrals for the four-loop Sudakov form factor
Boels, Rutger; Kniehl, Bernd A. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Yang, Gang [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Chinese Academy of Sciences, Beijing (China). Inst. of Theoretical Physics
2015-08-15
The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N=4) supersymmetric Yang-Mills theory (SYM) in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. Probably the simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was obtained in integrand form in a previous work for N=4 SYM, up to a single parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP) identities using (a tweaked version of) Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. The appearing master integrals are cross-checked using algebraic techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N=4 SYM and beyond are identified.
Excited state systematics in extracting nucleon electromagnetic form factors
Capitani, Stefano; von Hippel, Georg; Jäger, Benjamin; Knippschild, Bastian; Meyer, Harvey B; Rae, Thomas D; Wittig, Hartmut
2012-01-01
We present updated preliminary results for the nucleon electromagnetic form factors for non-perturbatively $\\mathcal{O}(a)$ improved Wilson fermions in $N_f=2$ QCD measured on the CLS ensembles. The use of the summed operator insertion method allows us to suppress the influence of excited states in our measurements. A study of the effect that excited state contaminations have on the $Q^2$ dependence of the extracted nucleon form factors may then be made through comparisons of the summation method to standard plateau fits, as well as to excited state fits.
Pion transition form factor through Dyson-Schwinger equations
Raya, Khépani
2016-01-01
In the framework of Dyson-Schwinger equations (DSE), we compute the $\\gamma^*\\gamma\\to\\pi^0$ transition form factor, $G(Q^2)$. For the first time, in a continuum approach to quantun chromodynamics (QCD), it was possible to compute $G(Q^2)$ on the whole domain of space-like momenta. Our result agrees with CELLO, CLEO and Belle collaborations and, with the well-known asymptotic QCD limit, $2f_\\pi$. Our analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor.
Pion Form Factor in the Light-Front
Pacheco-Bicudo-Cabral de Melo, J
2004-01-01
The pion electromagnetic form factor is calculated with a light-front quark model. The "plus" and "minus" component of the electromagnetic current are used to calculate the electromagnetic form factor in the Breit frame with two models for the q\\bar{q} vertex. The light front constituent quark models describes very well hadronic wave function for pseudo-scalar and vector particles. Symmetry problems arinsing in the light-front approach are solved by the pole dislocation method. The results are compared with new experimental data and with other quark models.
The B → K* form factors on the lattice
Agadjanov, Andria; Bernard, Véronique; Meißner, Ulf-G.; Rusetsky, Akaki
2016-09-01
The extraction of the B →K* transition form factors from lattice data is studied, applying non-relativistic effective field theory in a finite volume. The possible mixing of πK and ηK states is taken into account. The two-channel analogue of the Lellouch-Lüscher formula is reproduced. Due to the resonance nature of the K*, an equation is derived, which allows to determine the form factors at the pole position in a process-independent manner. The infinitely-narrow width approximation of the results is discussed.
The $B\\to K^*$ form factors on the lattice
Agadjanov, Andria; Meißner, Ulf-G; Rusetsky, Akaki
2016-01-01
The extraction of the $B\\to K^*$ transition form factors from lattice data is studied, applying non-relativistic effective field theory in a finite volume. The possible mixing of $\\pi K$ and $\\eta K$ states is taken into account. The two-channel analogue of the Lellouch-L\\"uscher formula is reproduced. Due to the resonance nature of the $K^*$, an equation is derived, which allows to determine the form factors at the pole position in a process-independent manner. The infinitely-narrow width approximation of the results is discussed.
Vector and Axial Form Factors Applied to Neutrino Quasielastic Scattering
Budd, H; Arrington, J
2005-01-01
We calculate the quasielastic cross sections for neutrino scattering on nucleons using up to date fits to the nucleon elastic electromagnetic form factors GEp, GEn, GMp, GMn, and weak form factors. We show the extraction of Fa for neutrino experiments. We show how well \\minerva, a new approved experiment at FNAL, can measure Fa. We show the that Fa has a different contribution to the anti-neutrino cross section, and how the anti-neutrino data can be used to check Fa extracted from neutrino scattering.