Strange and non-strange sea quark–gluon effects in nucleons

Proceedings of Sixth International Conference on Quarks and Nuclear Physics — PoS(QNP2012)

We generalize the approach of Brodsky et al. for the intrinsic charm quark distribution in the nucleons to the light-quark sector involving intrinsicū,d, s ands sea quarks. We compare the calculations with the existingd −ū, s +s, andū +d − s −s data. The good agreement between the theory and the data is interpreted as evidence for the existence of the intrinsic light-quark sea in the nucleons. The probabilities for the |uuduū , |uuddd and |uudss Fock states are also extracted.

Physical Review D, 1994

We suggest a general formalism to treat a baryon as a composite system of three quarks and a 'sea'. In this formalism, the sea is a cluster which can consists of gluons and quark-antiquark pairs. The hadron wave function with a sea component is given. The magnetic moments, related sum rules and axial weak coupling constants are obtained. The data seems to favor a vector sea rather than a scalar sea. The quark spin distributions in the nucleon are also discussed.

Journal of Physics: Conference Series, 2015

In this contribution, we discuss the spin and flavor content of the proton in the framework of the unquenched quark model, and address the role of valence and sea quarks in the nucleon.

1997

The intrinsic quark-antiquark pairs generated by the minimal energy nonperturbative rneson-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.

Physics Letters B

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0:003 < x < 0 : 7. From these asymmetries and the previously published inclusive spin asymmetries we determine, for the rst time, the x-dependent spin distributions for up and down valence quarks and for non-strange sea quarks. We nd that the rst moments of the valence quark spin distributions are u v = 1 : 01 0:19 0:14 and d v = 0:57 0:22 0:11. The spin distribution function of non-strange sea quarks is consistent with zero over the measured range of x and the rst moment i s u = d = 0 : 02 0:09 0:03.

Physics Letters B, 1996

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0:003 < x < 0 : 7. From these asymmetries and the previously published inclusive spin asymmetries we determine, for the rst time, the x-dependent spin distributions for up and down valence quarks and for non-strange sea quarks. We nd that the rst moments of the valence quark spin distributions are u v = 1 : 01 0:19 0:14 and d v = 0:57 0:22 0:11. The spin distribution function of non-strange sea quarks is consistent with zero over the measured range of x and the rst moment i s u = d = 0 : 02 0:09 0:03.

The European Physical Journal C, 2008

Within a statistical model of linear confined quarks we obtain the flavor asymmetry and corresponding structure function of the nucleon. The model parameters are fixed by the experimental available data. The temperature parameter is adjusted by the Gottfried sum rule violation and the chemical potentials by the corresponding up (u) and down (d) quark normalizations in the nucleon. The light antiquark and quark distributions in the proton, given by d/u, d/u and d − u, as well as the neutron to proton ratio of the structure functions, extracted from the experimental data, are well fitted by the model. As the quarkconfining strengths should be flavor dependent, a mechanism is introduced in the model to adjust the corresponding distribution, in order to improve the comparison obtained for the sea-quark asymmetries in the nucleon with the available experimental analysis.

Nuclear Physics B - Proceedings Supplements, 2010

Effective Quark mass shift, gluonic and pionic effects EFFECTIVE LIGHT QUARK MASS SHIFT The difference between the interaction of u and d quarks is supposed to come from instanton effects, which are flavour-spin dependent [Dorokhov et al, Sov.J.Part.Nucl. 23 (1992) 522].

A physical model for parton densities in hadrons, based on Gaussian momentum fluctuations of partons and hadronic baryon-meson fluctuations, is presented. The model has previously been shown to describe proton structure function data, and is now applied to sea quark asymmetries and shown to describe the dbar-ubar asymmetry of the proton. By considering fluctuations involving strange quarks, the model gives an asymmetry between the momentum distributions of s and sbar, which would reduce the significance of the NuTeV anomaly.

Progress in Particle and Nuclear Physics, 2001

A surprisingly large asymmetry between the up and down sea quark distributions in the nucleon has been observed in recent deep inelastic scattering and Drell-Yan experiments. This result strongly suggests that the mesonic degrees of freedom play an important role in the description of the parton distributions of the hadronic sea. In this article, we review the current status of our knowledge of the flavor structure of the nucleon sea. The implications of various theoretical models as well as possible future measurements are also discussed.