Longitudinal double-spin asymmetries in semi-inclusive deep-inelastic scattering of electrons and positrons by protons and deuterons

TL;DR

This paper reports comprehensive measurements of longitudinal double-spin asymmetries in semi-inclusive deep-inelastic scattering, providing insights into the nucleon's flavor structure and valence quark helicity distributions.

Contribution

It presents the full HERMES data set on spin asymmetries for charged pions and kaons, extending sensitivity to flavor structure beyond collinear frameworks.

Findings

No strong dependence of asymmetries on transverse momentum and azimuthal angle.

Charge-difference asymmetry offers access to valence quark helicity distributions.

Results enhance understanding of nucleon spin structure.

Abstract

A comprehensive collection of results on longitudinal double-spin asymmetries is presented for charged pions and kaons produced in semi-inclusive deep-inelastic scattering of electrons and positrons on the proton and deuteron, based on the full HERMES data set. The dependence of the asymmetries on hadron transverse momentum and azimuthal angle extends the sensitivity to the flavor structure of the nucleon beyond the distribution functions accessible in the collinear framework. No strong dependence on those variables is observed. In addition, the hadron charge-difference asymmetry is presented, which under certain model assumptions provides access to the helicity distributions of valence quarks.