Exclusive photoproduction of η_cγ and χ_cγ pairs in collinear factorization framework

In this talk we present our studies of exclusive η_cγ and χ_cγ photoproduction, and discuss the potential of these channels for phenomenological analysis of the generalized parton distributions of gluons in the Efremov-Radyushkin-Brodsky-Lepage kinematics. We found that in case of η_cγ, the dominant contribution comes from unpolarized GPD H_g, whereas photoproduction of χ_c1 γ and χ_c2 γ can also give access to other gluon GPDs of the target. We estimated numerically the cross sections and the expected counting rates in the kinematics of the middle-energy photoproduction experiments, which can be realized at the future Electron-Ion Collider or in the ultraperipheral collisions at LHC. We found that the cross sections of η_cγ and χ_cγ photoproduction are sufficiently large for dedicated experimental study. We also estimated the role of these processes as potential backgrounds to η_c and χ_c photoproduction, which are considered as possible gateways for studies of t-channel odderons. We found that the contributions of η_cγ and χ_cγ with undetected photon are on par with expected contributions of odderon-mediated mechanism in the kinematics of small momentum transfer |t| <0.5 GeV², though decrease rapidly at larger |t|.