Chiral constituent quarks and their role in quark distribution functions of nucleon and pion

Suzuki, Koshiro; Weise, W.

doi:10.1016/s0375-9474(98)00132-8

Cited by 55 publications

(65 citation statements)

References 70 publications

(99 reference statements)

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“…In the chiral quark model, the fluctuation of a bare constituent quark into a GS boson and a recoil bare constituent quark is given as [29] …”

Section: Isospin Symmetry Breaking In the Chiral Quark Modelmentioning

confidence: 99%

“…Such a form factor has the correct t-and u-channel symmetry, P jα/i (y) = P αj/i (1 − y). Then, one can obtain the quark-distribution functions in the proton [29],…”

Section: Isospin Symmetry Breaking In the Chiral Quark Modelmentioning

confidence: 99%

“…Usually, it is assumed that Λ K = Λ π = 1500 MeV [29,31]. However, it is implied by the SU(3) f symmetry breaking that P K should be smaller, and, accordingly, one should adopt a smaller Λ K .…”

Section: Isospin Symmetry Breaking In the Chiral Quark Modelmentioning

confidence: 99%

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Isospin symmetry breaking in the chiral quark model

Song

Zhang

2010

Phys. Rev. D

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We discuss the isospin symmetry breaking (ISB) of the valence-and sea-quark distributions between the proton and the neutron in the framework of the chiral quark model. We assume that isospin symmetry breaking is the result of mass differences between isospin multiplets and then analyze the effects of isospin symmetry breaking on the Gottfried sum rule and the NuTeV anomaly.We show that, although both flavor asymmetry in the nucleon sea and the ISB between the proton and the neutron can lead to the violation of the Gottfried sum rule, the main contribution is from the flavor asymmetry in the framework of the chiral quark model. We also find that the correction to the NuTeV anomaly is in an opposite direction, so the NuTeV anomaly cannot be removed by isospin symmetry breaking in the chiral quark model. It is remarkable that our results of ISB for both valence-and sea-quark distributions are consistent with the Martin-Roberts-Stirling-Thorne parametrization of quark distributions.

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“…In the chiral quark model, the fluctuation of a bare constituent quark into a GS boson and a recoil bare constituent quark is given as [29] …”

Section: Isospin Symmetry Breaking In the Chiral Quark Modelmentioning

confidence: 99%

“…Such a form factor has the correct t-and u-channel symmetry, P jα/i (y) = P αj/i (1 − y). Then, one can obtain the quark-distribution functions in the proton [29],…”

Section: Isospin Symmetry Breaking In the Chiral Quark Modelmentioning

confidence: 99%

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Isospin symmetry breaking in the chiral quark model

Song

Zhang

2010

Phys. Rev. D

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“…The fluctuation of a bare constituent quark into a Goldstone boson and a recoil bare constituent quark is given as [18] …”

Section: Chiral Quark Modelmentioning

confidence: 99%

Proton spin in a light-cone chiral quark model

Zhang

2012

Phys. Rev. D

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We discuss the spin structure of the proton in a light-cone treatment of the chiral quark model. Based on the fact that the quark helicity (∆q) measured in polarized deep inelastic scattering experiments is actually the quark spin defined in the light-cone formalism rather than the quark spin (∆qQM ) defined in the conventional quark model (or in the rest frame of the nucleon), we calculate the x dependence of the polarized quark distribution functions ∆q(x), and the polarized structure functions g1(x). Special attention is focused on the Melosh-Wigner rotation due to the transversal motions of quarks inside the nucleon and Melosh-Wigner rotation effects on the bare quark input. It is shown that our results match the experimental data well.

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“…Baryons are soliton solutions of the chiral Lagrangian in the limit of infinite quark colours (large AE ). Within the framework of this model the contribution of the quark spins was recently predicted to be ¡¦ ¼ at a scale of Î ¾ , while the remaining nucleon spin is carried by orbital angular momentum [59].…”

Section: The Spin Carried By the Quarksmentioning

confidence: 99%

Polarized Parton Distributions Measured at the HERMES Experiment

Wendland

2004

AIP Conference Proceedings

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The HERMES experiment at DESY, Germany was designed to carry out precision measurements of the proton spin structure using polarized deep-inelastic scattering. The experiment utilizes the ¾ Î electron or positron beam of the HERA accelerator which is longitudinally polarized at HERMES, in combination with a polarized internal gas target. For this work, data on longitudinally polarized hydrogen and deuterium targets were used to determine cross section asymmetries with respect to the alignment of the target and beam polarizations. Inclusive asymmetries on the proton and the deuteron, where only the scattered electron/positron is detected, were measured with high precision. In semi-inclusive deep-inelastic scattering, at least one final-state hadron is detected in coincidence. Semi-inclusive asymmetries of pions on the proton and pion and kaon asymmetries on the deuteron were measured for the first time by the HERMES collaboration. The measured asymmetries include detector effects and effects of higher-order processes in quantum electrodynamics.A new unfolding procedure that takes into account the correlations between kinematic bins was implemented to correct for these effects.The polarized parton densities of the up, down, and sea flavours were obtained from the unfolded inclusive and semi-inclusive asymmetries in a probabilistic analysis based on leading-order quantum chromodynamics. In the case of the up quark and the down quark, the polarized densities were determined to be positive and negative, respectively. The polarized densities of the sea flavours, decomposed for the first time into the densities of the anti-up, anti-down, and strange quarks, were found to be compatible with zero. Moments of the polarized parton densities were computed. TheBjørken sum rule was verified and the total spin carried by the quark spins was determined to bé ¿ ¼ ¦ ¼µ ±. This latter result is larger than earlier measurements but still smaller than ¼ ± predicted in relativistic models of the proton.iii iv ABSTRACT AcknowledgementsFirst of all I would like to thank my adviser, Dr. Michel Vetterli, for providing the opportunity to conduct research on the nucleon spin structure. His support towards the completion of this work was indispensable. I would also like to thank the members of the ¡Õ-group, notably Thore Lindemann and Marc Beckmann, whose collaboration was invaluable.My thanks go to Elke Aschenauer for her tremendous efforts in running the experiment and in contributing to the analysis. I am indebted to Naomi Makins for the numerous discussions we had.

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Chiral constituent quarks and their role in quark distribution functions of nucleon and pion

Cited by 55 publications

References 70 publications

Isospin symmetry breaking in the chiral quark model

Isospin symmetry breaking in the chiral quark model

Proton spin in a light-cone chiral quark model

Polarized Parton Distributions Measured at the HERMES Experiment

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