Quark-antiquark asymmetry of helicity distributions in the nucleon sea

摘要

We study the helicity distributions of light flavor quark-antiquark ( q q ˉ ) 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 q ˉ pairs are treated from statistical consideration by introducing the helicity suppression factors l q ( x ) and l ˉ q ( x ) to parametrize the helicity distributions of q-flavor sea quark and antiquark respectively, while Δ l q ( x ) = l q ( x ) ? l ˉ q ( x ) represents a combined effect of helicity contribution due to sea q q ˉ pairs. From fitting the nucleon polarization asymmetries A 1 N in inclusive deep inelastic scattering processes and the single-spin asymmetries A L W ± 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 q ˉ pairs, i.e., Δ q s ( x ) ≠ Δ q ˉ s ( x ) , plays an important role for a comprehensive understanding of the nucleon spin content.