Single Spin Asymmetry in Charmonium Production

TL;DR

This paper estimates the single spin asymmetry in J/psi electroproduction, incorporating TMD evolution of the gluon Sivers function, and finds the asymmetries are smaller with TMD evolution than with DGLAP, but similar to previous TMD estimates.

Contribution

It introduces a detailed calculation of SSA in charmonium production using TMD evolution of the gluon Sivers function, improving upon previous estimates.

Findings

SSA is smaller with TMD evolution compared to DGLAP.

SSA estimates are consistent with previous TMD-based calculations.

Results are relevant for experiments at JLab, HERMES, COMPASS, and eRHIC.

Abstract

We present estimates of Single Spin Asymmetry (SSA) in the electroproduction of $J/\psi$ taking into account the transverse momentum dependent (TMD) evolution of the gluon Sivers function and using Color Evaporation Model of charmonium production. We estimate SSA for JLab, HERMES, COMPASS and eRHIC energies using recent parameters for the quark Sivers functions which are fitted using an evolution kernel in which the perturbative part is resummed up to next-to-leading logarithms (NLL) accuracy. We find that these SSAs are much smaller as compared to our first estimates obtained using DGLAP evolution but are comparable to our estimates obtained using TMD evolution where we had used approximate analytical solution of the TMD evolution equation for the purpose.