Single transverse-spin asymmetry for direct-photon and single-jet productions at RHIC

TL;DR

This paper predicts sizable single transverse-spin asymmetries in direct-photon and jet productions at RHIC, emphasizing the dominance of soft-gluon pole contributions and the potential to probe three-gluon correlations.

Contribution

It provides the first comprehensive prediction of asymmetries in these processes based on twist-3 mechanisms, highlighting the role of three-gluon correlations.

Findings

Sizable asymmetries in the forward region of the polarized proton.

Asymmetries are nearly zero in the backward region unless three-gluon correlations are involved.

Soft-gluon pole contributions dominate over soft-fermion poles.

Abstract

We study the single transverse-spin asymmetry for the inclusive direct-photon and single-jet productions in the proton-proton collision based on the twist-3 mechanism in the collinear factorization. Taking into account all the effects from the twist-3 quark-gluon correlation functions inside a transversely polarized proton, we present a prediction for the asymmetries at the typical RHIC kinematics. In both processes we find sizable asymmetries in the forward region of the polarized proton while they are almost zero in the backward region. This implies that if one finds a nonzero asymmetries in the backward region in these processes, it should be ascribed wholely to the three-gluon correlations. We also find the soft-gluon pole contribution is dominant and the soft-fermion pole contribution is negligible in the whole Feynman-x region for these asymmetries.