Transverse single spin asymmetry in hadronic $\eta_{c,b}$ production

TL;DR

This paper investigates the transverse single spin asymmetry in eta_c and eta_b production during polarized hadron collisions, confirming theoretical consistency and identifying a previously overlooked term affecting tri-gluon correlations.

Contribution

It introduces a detailed analysis of the twist-3 Efremov-Teryaev-Qiu-Sterman function's role in spin asymmetries and uncovers a new term influencing tri-gluon correlation evolution.

Findings

Confirmed consistency between collinear twist-3 and TMD approaches at small transverse momentum.

Identified a previously missed term in the scale evolution of tri-gluon correlations.

Provided insights into the spin-dependent cross section contributions in heavy quarkonium production.

Abstract

We study the transverse single spin asymmetry in $\eta_{c,b}$ production in polarized hadron collisions, employing the collinear twist-3 approach in combination with the color singlet model. Our main focus lies on the contribution from the twist-3 Efremov-Teryaev-Qiu-Sterman function. By extrapolating the derived spin dependent cross section to the small transverse momentum region, consistency between the collinear twist-3 approach and the transverse momentum dependent factorization approach is confirmed. As a byproduct of this work, we identify a term contributing to the scale evolution of tri-gluon correlations in the flavor-singlet case which was previously missed.