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

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 nonpole 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.