A new twist-3 analysis of the single transverse-spin asymmetry for pion and kaon production at RHIC

TL;DR

This paper introduces a new twist-3 collinear factorization analysis of single transverse-spin asymmetries in pion and kaon production at RHIC, emphasizing the importance of both soft-gluon-pole and soft-fermion-pole contributions for accurate data description.

Contribution

It presents a novel comprehensive twist-3 analysis including both SGP and SFP contributions, improving the understanding of SSA mechanisms in hadron production at RHIC.

Findings

SGP contribution alone is insufficient to explain RHIC data.

Including SFP contributions significantly improves data description.

The model accurately reproduces the P_T-dependence of A_N and K^- asymmetries.

Abstract

We present a new analysis for the single-transverse spin asymmetry (SSA) for the inclusive pion and kaon productions in the proton-proton collisions measured at RHIC. The framework we use is the collinear factorization in which SSA appears as a twist-3 observable resulting from the multiparton correlations in the hadrons. As a relevant multiparton correlation, we include all the contributions associated with the quark-gluon correlation functions in the transversely polarized proton, i.e., those from the soft-gluon-pole (SGP) and the soft-fermion-pole (SFP). We have found that the SGP contribution alone is insufficient to describe the observed RHIC A_N data and the inclusion of the SFP contribution plays an important role for the improved description of the data. In particular, P_T-dependence of A_N and A_N for K^- have been well described in our new analysis.