Collinear Twist-3 Approach to Transverse Single-Spin Asymmetry in Proton-Proton Collision

TL;DR

This paper analyzes the transverse single-spin asymmetry in proton-proton collisions, incorporating twist-3 quark-gluon correlations and fragmentation effects, with functions constrained by previous experimental data to ensure consistency.

Contribution

It provides a comprehensive twist-3 analysis of SSA in pp collisions, integrating multiple effects and fixing functions based on prior data to resolve sign mismatch issues.

Findings

Consistent description of SSA data in pp collisions

Inclusion of twist-3 fragmentation effects

Resolution of sign mismatch problem

Abstract

We present our recent analysis on the transverse single-spin asymmetry (SSA) in inclusive pion and direct-photon production in pp collisions for RHIC kinematics. The analysis includes the contributions from twist-3 quark-gluon-quark correlations in the proton and twist-3 fragmentation effects for the pion. Some of the functions appearing in the formula for the SSA, such as the soft-gluon-pole Qiu-Sterman function, the nucleon transversity, and the Collins function were fixed consistently with the SSA data in semi-inclusive DIS and in e+e- annihilation, so that our analysis is free from the sign mismatch problem.