Collins Fragmentation and the Single Transverse Spin Asymmetry

TL;DR

The Collins mechanism for the single transverse spin asymmetry in the collinear factorization approach is studied and the corresponding twist-three fragmentation function is identified.

Abstract

We study the Collins mechanism for the single transverse spin asymmetry in the collinear factorization approach. The correspondent twist-three fragmentation function is identified. We show that the Collins function calculated in this approach is universal. We further examine its contribution to the single transverse spin asymmetry of semi-inclusive hadron production in deep inelastic scattering and demonstrate that the transverse momentum dependent and twist-three collinear approaches are consistent in the intermediate transverse momentum region where both apply.

Figures (2)

• Figure 1: Typical Feynman diagrams for the transverse momentum dependent Collins fragmentation function calculated in the collinear factorization approach: contributions from (a) $\partial_\perp$ and (b) $A_\perp$ associated operators in the twist-three quark-gluon correlation functions.
• Figure 2: Typical Feynman diagrams for the Collins mechanism contributions to the single spin asymmetry in semi-inclusive deep inelastic scattering. Again, we will have contributions from (a) $\partial_\perp$ and (b) $A_\perp$ associated operators in the twist-three quark-gluon correlation functions.