The photoproduction of η_cγ and χ_cγ pairs in the small-x kinematics

In this talk we discuss the photoproduction of the η_cγ and χ_cγ charmonia-photon pairs with large invariant mass. We focus on the high energy (small-x) kinematics, and use the Color Glass Condensate framework for analysis. We estimated numerically the cross-sections and the expected counting rates in the kinematics of the ultraperipheral collisions at LHC and high-energy runs at the future Electron Ion Collider, and found that they are sufficiently large for experimental study. The cross-sections of the suggested processes are controlled by the forward color dipole scattering amplitude of the target, and the kinematic distributions of the produced charmonia-photon pairs have straightforward relation to the dependence of the dipole amplitude on the variables that characterize the dipole. We also analyzed the role of these processes as potential backgrounds to exclusive photoproduction of η_c and χ_c mesons, which have been recently suggested as promising channels for studies of odderons. We found that the cross-sections of η_cγ and χ_cγ pairs with undetected photons are comparable to those of odderons at small momentum transfer |t| ≤ 1 GeV², but become less relevant at larger |t| . We also found that the dominant background to odderon-mediated production of η_c and χ_c comes from the radiative decays J/ψ→η_cγ and ψ(2S)→χ_cγ , and can present challenges for odderon studies via charmonia production.