Quark-antiquark asymmetry of helicity distributions in the nucleon sea

TL;DR

This paper investigates the helicity distributions of light quark-antiquark pairs in the nucleon sea, revealing a significant asymmetry between quark and antiquark helicity distributions that impacts our understanding of nucleon spin.

Contribution

It introduces a statistical model with helicity suppression factors to describe sea quark helicity distributions and fits experimental data to reveal quark-antiquark asymmetry.

Findings

Significant quark-antiquark helicity asymmetry found

Helicity suppression factors effectively model sea quark distributions

Asymmetry impacts nucleon spin structure understanding

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 $A^N_1$ in inclusive deep inelastic scattering processes and the single-spin asymmetries $A^{W^{\pm}}_L$ 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., $\Delta q_s(x) \neq \Delta \bar q_s(x)$, plays an important role for a comprehensive understanding of the nucleon spin content.