Azimuthal asymmetries in $J/\psi$-photon production at the EIC

TL;DR

This paper investigates azimuthal asymmetries in $J/eta$-photon production at the EIC using TMD factorization, highlighting the independence from LDMEs and potential to probe gluon TMDs.

Contribution

It demonstrates that azimuthal asymmetries in $J/\psi$-photon production are independent of LDMEs and can serve as direct probes of gluon TMDs at the EIC.

Findings

Azimuthal asymmetries are independent of LDMEs due to color octet dominance.

Upper bounds of asymmetries are estimated using positivity bounds.

Gaussian parametrization provides additional estimates of asymmetries.

Abstract

We calculate azimuthal asymmetries in back-to-back production of $J/\psi$ and a photon in electron-proton scattering process at the future electron-ion collider (EIC) using TMD factorization framework. We consider the cases where the proton is unpolarized or transversely polarized. For the formation of $J/\psi$, non-relativistic QCD (NRQCD) is used. We find that the cross-section gets contribution from only one color octet state, as a result, the azimuthal modulations become independent of the long-distance matrix elements (LDMEs), and thus can be used to probe, in particular the gluon TMDs which are dominant in this kinematics. We show estimates of the upper bounds of different azimuthal asymmetries using the positivity bounds on TMDs. In addition, we show estimate of asymmetries using the Gaussian parametrization of the TMDs.