The exclusive photoproduction of $χ_{c}γ$ pairs in the small-$x$ kinematics

Abstract

In this manuscript we analyze the exclusive photoproduction of the $χ_{c}γ$ pairs. We focus on the small-$x$ kinematics and evaluate the cross-sections in the Color Glass Condensate framework. We found that in the leading order in the strong coupling $α_{s}$, this process is sensitive only to the forward color dipole scattering amplitude. We estimated numerically the cross-sections for different polarizations of $χ_{c}$ mesons in the kinematics of the ultraperipheral collisions at LHC and the future Electron Ion Collider. We also analyzed the role of this process as a potential background to exclusive $χ_{c}$ photoproduction, which has been recently suggested as an alternative channel for studies of odderons. According to our estimates, the cross-section of $χ_{c}γ$ with undetected photons is comparable to that of odderons at small momentum transfer $|t|\lesssim1$ GeV$^{2}$, but becomes less relevant at larger $|t|$. We also found that a dominant background to odderon-mediated production of $χ_{c}$ comes from the radiative decays of $ψ(2S)$ mesons, which potentially can present a challenge for odderon studies via $χ_{c}$ photoproduction.