Quark-antiquark asymmetry of helicity distributions in the nucleon sea

Abstract

We study the helicity distributions of light flavor quark-antiquark (qq̄) pairs in the nucleon sea. The valence quarks are handled by adopting the light-cone SU(6) quark-spectator-diquark model and the sea qq̄ pairs are treated from statistical consideration by introducing the helicity suppression factors lq(x) and l̄q(x) to parametrize the helicity distributions of q-flavor sea quark and antiquark respectively, while Δlq(x)=lq(x)-l̄q(x) represents a combined effect of helicity contribution due to sea qq̄ pairs. From fitting the nucleon polarization asymmetries A1N in inclusive deep inelastic scattering processes and the single-spin asymmetries ALW± 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 qq̄ pairs, i.e., Δqs(x)≠Δq̄s(x), plays an important role for a comprehensive understanding of the nucleon spin content.