The exclusive photoproduction of ${\chi }_c\gamma$ pairs in the small-$x$ kinematics

Abstract

In this manuscript we analyze the exclusive photoproduction of the ${\chi }_c\gamma$ 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 ${\alpha }_s$, this process is sensitive only to the forward color dipole scattering amplitude. We estimated numerically the cross-sections for different polarizations of ${\chi }_c$ 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 ${\chi }_c$ photoproduction, which has been recently suggested as an alternative channel for studies of odderons. According to our estimates, the cross-section of ${\chi }_c\gamma$ with undetected photons is comparable to that of odderons at small momentum transfer $|t|\lesssim 1$ GeV${}^2$, but becomes less relevant at larger $|t|$. We also found that a dominant background to odderon-mediated production of ${\chi }_c$ comes from the radiative decays of $\psi (2S)$ mesons, which potentially can present a challenge for odderon studies via ${\chi }_c$ photoproduction.

Comments: 32 pages, 13 figures