On the Relation Between Mechanisms for Single-Transverse-Spin Asymmetries

TL;DR

This paper demonstrates the consistency between twist-three and transverse-momentum-dependent mechanisms for single-transverse-spin asymmetries, extending previous overlap studies to include additional pole contributions in semi-inclusive deep inelastic scattering.

Contribution

It extends the understanding of the relation between two mechanisms for spin asymmetries by including soft-fermion poles and additional twist-three functions, confirming their mutual consistency.

Findings

Soft-fermion pole contributions are consistent with existing mechanisms.

Additional twist-three functions organize to maintain mechanism compatibility.

The study confirms the unified description of single-spin asymmetries.

Abstract

Recent studies have shown that two widely-used mechanisms for single-transverse-spin asymmetries based on either twist-three contributions or on transverse-momentum-dependent (Sivers) parton distributions become identical in a kinematical regime of overlap. This was demonstrated for the so-called soft-gluon-pole and hard-pole contributions to the asymmetry associated with a particular quark-gluon correlation function in the nucleon. In this paper, using semi-inclusive deep inelastic scattering as an example, we extend the study to the contributions by soft-fermion poles and by another independent twist-three correlation function. We find that these additional terms organize themselves in such a way as to maintain the mutual consistency of the two mechanisms for single-spin asymmetries.