A New Mechanism for Generating a Single Transverse Spin Asymmetry

TL;DR

This paper introduces a novel mechanism for generating single transverse spin asymmetries in high-energy proton collisions, involving q->q G splitting and odderon interactions, aligning qualitatively with experimental observations.

Contribution

It presents a new theoretical framework linking q->q G splitting and odderon interactions to STSA, predicting smaller asymmetries in proton-nucleus collisions and zero asymmetry for prompt photons.

Findings

STSA decreases with decreasing x_F

STSA peaks near the saturation scale Q_s

STSA for prompt photons is zero

Abstract

We propose a new mechanism for generating a single transverse spin asymmetry (STSA) in polarized proton-proton and proton-nucleus collisions in the high-energy scattering approximation. In this framework the STSA originates from the q->q G splitting in the projectile (proton) light-cone wave function followed by a perturbative (C-odd) odderon interaction, together with a C-even interaction, between the projectile and the target. We show that some aspects of the obtained expression for the STSA of the produced quarks are in qualitative agreement with experiment: STSA decreases with decreasing projectile x_F and is a non-monotonic function of the transverse momentum k_T. In our framework the STSA peaks at k_T near the saturation scale Q_s. Our mechanism predicts that the quark STSA in proton-nucleus collisions should be much smaller than in proton-proton collisions. We also observe that in our formalism the STSA for prompt photons is zero.