Azimuthal asymmetries in semi-inclusive $J/\psi +\mathrm{jet}$ production at an EIC

Abstract

We consider transverse momentum dependent gluon distributions inside both unpolarized and transversely polarized protons and show how they can be probed by looking at azimuthal modulations in $ep\to eJ/\psi \mathrm{jet}X$. We find that the contribution due to quark induced subprocesses is always suppressed in the considered kinematic regions, accessible in principle at a future Electron-Ion Collider. Our model-independent estimates of the maximal values of these asymmetries allowed by positivity bounds suggest the feasibility of their measurement. In addition, by adopting the McLerran-Venugopalan model for the unpolarized and linearly polarized gluon densities, we study the behavior of the $\cos 2\varphi$ asymmetries in the small-$x$ limit.

Comments: 15 pages, 8 figures; v2: conclusions expanded, references added, matches published version