Quark-antiquark asymmetry of helicity distributions in the nucleon sea

Abstract

We study the helicity distributions of light flavor quark-antiquark ($q\bar{q}$) pairs in the nucleon sea. The valence quarks are handled by adopting the light-cone SU(6) quark-spectator-diquark model and the sea $q\bar{q}$ pairs are treated from statistical consideration by introducing the helicity suppression factors $l_q(x)$ and ${\bar{l}}_q(x)$ to parametrize the helicity distributions of q-flavor sea quark and antiquark respectively, while $\Delta l_q(x)=l_q(x)-{\bar{l}}_q(x)$ represents a combined effect of helicity contribution due to sea $q\bar{q}$ pairs. From fitting the nucleon polarization asymmetries $A_1^N$ in inclusive deep inelastic scattering processes and the single-spin asymmetries $A_L^{W^{\pm }}$ in Drell-Yan type processes, we find a significant asymmetry between the quark and antiquark helicity distributions of the nucleon sea. Therefore the quark-antiquark asymmetry of helicity distributions of nucleon sea $q\bar{q}$ pairs, i.e., $\Delta q_s(x)\ne \Delta {\bar{q}}_s(x)$, plays an important role for a comprehensive understanding of the nucleon spin content.

Comments: 10 latex pages, 5 figures, final version to appear in PRD