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Extraction of Various Five-Quark Components of the Nucleons  [PDF]
Wen-Chen Chang,Jen-Chieh Peng
Physics , 2011, DOI: 10.1016/j.physletb.2011.08.077
Abstract: We have generalized the approach of Brodsky {\it et al.} for the intrinsic charm quark distribution in the nucleons to the light-quark sector involving intrinsic $\bar u, \bar d, s$ and $\bar s$ sea quarks. We compare the calculations with the existing $\bar d - \bar u$, $s + \bar s$, and $\bar u + \bar d - s -\bar s$ data. The good agreement between the theory and the data allows the extraction of the probabilities for the $|uudu\bar{u}>$, $|uudd\bar{d}>$, and $|uuds\bar{s}>$ five-quark Fock states in the proton. We also calculate the $x$-dependence of the intrinsic charm after taking into consideration the QCD evolution of the intrinsic quark distribution.
Light quark distributions in the proton sea  [PDF]
Mary Alberg,Ernest M. Henley
Physics , 1999, DOI: 10.1016/S0375-9474(99)00600-4
Abstract: We use the meson cloud model to calculate $\bar{d}(x) - \bar{u}(x)$ and $ \bar{d}(x)/\bar{u}(x)$ in the proton. We show that a modification of the symmetric, perturbative part of the light quark sea provides better agreement with the ratio $ \bar{d}(x)/\bar{u}(x).
The Spin and Flavor Content of Intrinsic Sea Quarks  [PDF]
B. -Q. Ma,S. J. Brodsky
Physics , 1997,
Abstract: The intrinsic quark-antiquark pairs generated by the minimal energy nonperturbative meson-baryon fluctuations in the nucleon sea provide a consistent framework for understanding a number of empirical anomalies observed in the deep inelastic quark-parton structure of nucleons: the flavor asymmetry of the nucleon sea implied by the violation of Gottfried sum rule, the proton spin problem implied by the violation of the Ellis-Jaffe sum rule, and the outstanding conflict between two different determinations of the strange quark sea in the nucleon.
The impact of the intrinsic charm quark content of the proton on differential $γ+c$ cross section  [PDF]
S. Rostami,A. Khorramian,A. Aleedaneshvar,M. Goharipour
Physics , 2015,
Abstract: We present a comparative analysis of the impact of the non-perturbative intrinsic charm quark content of the proton on differential cross section of $\gamma +c $-jet in $ pp $ and $ p\bar{p} $ collisions, for the kinematic regions that are sensitive to this contribution. We discuss the $ Q^2 $ evolution of intrinsic quark distributions and present a code which provide these distributions as a function of $ x $ and $ Q^2 $ for any arbitrary Fock state probability. For the $ p\bar{p} $ collisions at the Tevatron, the results are compared with the recent experimental data of D0 at $\sqrt{s} =1.96$ TeV and also predictions for $ pp $ collisions at $\sqrt{s} =8$ TeV and $\sqrt{s} =13$ TeV for the LHC.
Detailed Balance and Sea-Quark Flavor Asymmetry of Proton  [PDF]
Yong-Jun Zhang,Bin Zhang,Bo-Qiang Ma
Physics , 2001, DOI: 10.1016/S0370-2693(01)01266-7
Abstract: In this study, the proton is taken as an ensemble of quark-gluon Fock states. Using the principle of detailed balance, the probabilities of finding every Fock states of the proton are obtained without any parameter. A new origin of the light flavor sea quark asymmetry, i.e., $\bar{u} \not= \bar{d}$, is given as a pure statistical effect. It is found that $\bar{d}-\bar{u} \approx 0.124$, which is in surprisingly agreement with the experimental observation.
Structural Aspects of the Proton in the Chiral Quark Model  [PDF]
Chung-Yi Wu
Physics , 1995, DOI: 10.1142/S0217732397001175
Abstract: We calculate with chiral symmetry the parton contents of the proton based on a two-component wave function. The calculation results give significant sea-quark contents and, especially, the intrinsic gluon polarization produced at a more fundamental level.
Flavor asymmetry of the polarized sea-quark distributions in the proton  [PDF]
M. Wakamatsu
Physics , 2010,
Abstract: The recent global analysis of helicity parton distributions, which takes into account available data from inclusive and semi-inclusive polarized deep inelastic scattering, as well as from polarized proton-proton scattering at RHIC, appears to offer the first strong evidence that polarized sea-quark distributions are flavor asymmetric, i.e. $\Delta \bar{u}(x) \ne \Delta \bar{d}(x)$. We point out that the flavor symmetry breaking pattern indicated by their analysis, i.e. $\Delta \bar{u}(x) > 0$ and $\Delta \bar{d}(x) < 0$ with the magnitude correlation $|\Delta \bar{u}(x)| < |\Delta \bar{d}(x)|$, is just consistent with our theoretical predictions given several years ago on the basis of the chiral quark soliton model. We also address ourselves to understanding the physics behind this observation.
Recent results of gluon and sea quark polarization measurements in polarized proton-proton collisions at STAR  [PDF]
Xuan Li
Physics , 2014, DOI: 10.1088/1742-6596/535/1/012003
Abstract: The STAR experiment at RHIC is carrying out a comprehensive high-energy spin physics program to understand the internal structure and dynamics of the proton in polarized proton-proton collisions at $\sqrt{s} = 200$ GeV and $\sqrt{s} = 500/510$ GeV. STAR has the capability, with nearly full azimuthal coverage, to reconstruct leptons, hadrons and jets in the mid-rapidity region ($|\eta|<1$). The results for inclusive jet longitudinal double spin asymmetries taken during the 2009 RHIC run indicate the first non-zero gluon contribution ($\Delta g(x,Q^{2}) / g(x,Q^{2})$) to the proton spin for $0.05
The Quark/Antiquark Asymmetry of the Nucleon Sea  [PDF]
S. J. Brodsky,B. -Q. Ma
Physics , 1996, DOI: 10.1016/0370-2693(96)00597-7
Abstract: Although the distributions of sea quarks and antiquarks generated by leading-twist QCD evolution through gluon splitting $g \rightarrow \bar q q$ are necessarily CP symmetric, the distributions of nonvalence quarks and antiquarks which are intrinsic to the nucleon's bound state wavefunction need not be identical. In this paper we investigate the sea quark/antiquark asymmetries in the nucleon wavefunction which are generated by a light-cone model of energetically-favored meson-baryon fluctuations. The model predicts striking quark/antiquark asymmetries in the momentum and helicity distributions for the down and strange contributions to the proton structure function: the intrinsic $d$ and $s$ quarks in the proton sea are predicted to be negatively polarized, whereas the intrinsic $\bar d$ and $\bar s$ antiquarks give zero contributions to the proton spin. Such a picture is supported by experimental phenomena related to the proton spin problem and the violation of the Ellis-Jaffe sum rule. The light-cone meson-baryon fluctuation model also suggests a structured momentum distribution asymmetry for strange quarks and antiquarks which could be relevant to an outstanding conflict between two different determinations of the strange quark sea in the nucleon. The model predicts an excess of intrinsic $d \bar d$ pairs over $u \bar u$ pairs, as supported by the Gottfried sum rule violation. We also predict that the intrinsic charm and anticharm helicity and momentum distributions are not identical.
The Proton Spin Structure in a Light-Cone Qaurk-Spectator-Diquark Model  [PDF]
Bo-Qiang Ma
Physics , 1997,
Abstract: It is shown that the proton spin problem raised by the Ellis-Jaffe sum rule violation does not in conflict with the SU(6) quark model, provided that the relativistic effect from the quark transversal motions, the flavor asymmetry between the $u$ and $d$ valence quarks, and the intrinsic quark-antiquark pairs generated by the non-perturbative meson-baryon fluctuations of the nucleon sea are taken into account. The meson-baryon fluctuations of the nucleon sea provide a consistent picture for connecting the proton spin structure with a number of other anomalies observed in the proton's structure, such as the flavor asymmetry of the nucleon sea implied by the violation of the Gottfried sum rule and the discrepancy between two different measurements of the strange quark distributions in the nucleon sea.
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