Contribution of twist-3 fragmentation function to single transverse-spin asymmetry in semi-inclusive deep inelastic scattering

TL;DR

This paper develops a formalism to calculate the contribution of twist-3 fragmentation functions to single transverse-spin asymmetries in semi-inclusive deep inelastic scattering, ensuring gauge invariance and providing a complete cross-section formula.

Contribution

It introduces a new formalism using Ward-Takahashi identity in Feynman gauge to compute twist-3 fragmentation effects in SIDIS, including non-pole contributions.

Findings

Derived the complete cross-section formula at leading order

Established the gauge-invariance of the hadronic tensor

Analyzed small transverse-momentum behavior of structure functions

Abstract

We study the contribution of the twist-3 fragmentation function to the single-transverse spin asymmetry in semi-inclusive deep inelastic scattering within the framework of the collinear factorization. Making use of the Ward-Takahashi identity in QCD, we establish the formalism in the Feynman gauge to calculate the non-pole contribution of the twist-3 fragmentation function to the asymmetry and derive the complete cross-section formula in the leading order QCD perturbation theory. The obtained twist-3 hadronic tensor is shown to satisfy the electromagnetic gauge-invariance. The behavior in the small transverse- momentum region for the five structure functions is also given.