Unraveling Gluon TMDs in $J/\psi$ and Pion production at the EIC

TL;DR

This paper explores gluon and quark transverse momentum-dependent distributions through azimuthal asymmetries in $J/eta$ and pion production at the EIC, highlighting the dominance of gluon contributions and providing numerical estimates for asymmetries.

Contribution

It introduces a detailed analysis of gluon TMDs in $J/eta$ and pion production using the TMD factorization framework, emphasizing gluon dominance and providing numerical bounds for asymmetries.

Findings

Gluon contributions dominate azimuthal asymmetries.

Numerical estimates of asymmetries are provided for EIC kinematics.

Gluon TMDs are modeled with Gaussian parametrization.

Abstract

We investigate the azimuthal asymmetries such as $\cos2{\phi_T}$ and Sivers symmetry for $J/\psi$ and $\pi^\pm$ production in electron-proton scattering, focusing on scenarios where the $J/\psi$ and the pion are produced in an almost back-to-back configuration. The electron is unpolarized, while the proton can be unpolarized or transversely polarized. For the $J/\psi$ formation, we use non-relativistic QCD (NRQCD), while $\pi^\pm$ is formed due to parton fragmentation. In this kinematics, we utilize the transverse momentum-dependent factorization framework to calculate the cross sections and asymmetries. We consider both quark and gluon-initiated processes and show that the gluon contribution dominates. We provide numerical estimates of the upper bounds on the azimuthal asymmetries, as well as employ a Gaussian parametrization for the gluon transverse momentum distributions (TMDs), within the kinematical region accessible by the upcoming Electron-Ion Collider (EIC).