Light flavor asymmetry of nucleon sea

Abstract

The light flavor antiquark distributions of the nucleon sea are calculated in the effective chiral quark model and compared with experimental results. The contributions of the flavor-symmetric seaquark distributions and the nuclear EMC effect are taken into account to obtain the ratio of Drell-Yan cross sections σ pD /2σ pp , which can match well with the results measured in the FermiLab E866/NuSea experiment. The calculated results also match the measuredd(x) −ū(x) from different experiments, but unmatch the behavior ofd(x)/ū(x) derived indirectly from the measurable quantity σ pD /2σ pp by the FermiLab E866/NuSea Collaboration at large x. We suggest to measure againd(x)/ū(x) at large x from precision experiments with careful experimental data treatment. We also propose an alternative procedure for experimental data treatment.

Unpolarized TMD Quark Distribution Functions at Low $Q^2$ Scales

“…In this model, proton is considered as a bounded system of bare u and d quarks (u 0 , d 0 ). In this system, the clouds of Goldstone (GS) bosons and gluons surround the bare quarks [12,13,14]. At the first approximation, two basic interactions are occurred in the χQM which are represented…”

“…[7] in Fig.1. For the interaction of Fig.1(a), the distribution of j quark is written as [12,13,14]:…”

“…jB denotes the squared invariant mass of the final quark-GS boson state [12,13,14]. On the other hand, the interaction of Fig.1(b) is formulated as follows [14]:…”

Proton spin in a light-cone chiral quark model

“…In this model, the minor effects of the internal gluons are neglected, and the valence quarks contained in the nucleon fluctuate into quarks plus Goldstone bosons, which spontaneously break the chiral symmetry. This model is successful in explaining a number of problems, including the violation of the Gottfried sum rule from the aspect of the flavor asymmetry in the nucleon sea [12][13][14], the NuTeV anomaly resulting from the strange-antistrange asymmetry [15], and the isospin symmetry breaking between the proton and the neutron [16]. It is also proposed by Cheng and Li [17] that the proton spin problem can be accounted for by the quark splitting into a quark plus a Goldstone boson in the chiral quark model from an intuitive argument.…”

“…However, in the chiral quark model, only the intrinsic sea is calculated while the extrinsic sea is left out. Therefore, it is generally necessary to add the extrinsic sea before comparing results with experiments when we consider the unpolarized quark distributions [14]. Nevertheless, when we consider the polarized quark distributions, we assume that the perturbative extrinsic sea is totally unpolarized, since the correlative processes give equal contributions to both types of polarization.…”