Exclusive photoproduction of $\eta_{c}\gamma$ pairs with large invariant mass

Abstract

In this preprint we analyzed the exclusive photoproduction of $\eta_{c}\gamma$ pairs in the collinear factorization framework and evaluated its cross-section in leading order in the strong coupling $\alpha_{s}$. We found that this process is mostly sensitive to the behavior of the unpolarized gluon GPD $H_{g}$ in the Efremov-Radyushkin-Brodsky-Lepage kinematics. We estimated numerically the cross-section and the expected counting rates in the kinematics of middle-energy photoproduction experiments which can be realized at the future Electron-Ion Collider and in the kinematics of ultraperipheral collisions at LHC. We found that the cross-section is sufficiently large for dedicated experimental study.