Exclusive process $\gamma \gamma \rightarrow J/\psi+\gamma$ production in ultraperipheral proton and nuclear collisions at the HL-LHC and FCC

Abstract

We present a next-to-leading-order (NLO) analysis of exclusive $J/\psi+\gamma$ production via photon-photon fusion in ultraperipheral collisions at the High-Luminosity Large Hadron Collider (HL-LHC) and the Future Circular Collider (FCC). The study is performed within the NRQCD factorization framework for proton-proton, proton-nucleus, and nucleus-nucleus collisions, with nuclear species spanning a wide range of nuclear charges (O, Ca, Ar, Kr, Xe, and Pb), enabling a systematic investigation of nuclear effects on the production cross sections. The photon fluxes are modeled using an electric-dipole form factor, with the impact-parameter dependence strictly enforced to ensure the exclusivity of the process. We present predictions for total cross sections and kinematic distributions at leading order and NLO. With a transverse momentum cut of $p_T > 2\,\mathrm{GeV}$, the NLO corrections reduce the cross section by approximately $35\%$ at the central scale. The associated theoretical uncertainties are systematically estimated via renormalization scale variations. Despite this suppression, the cross sections remain sizable and indicate that exclusive $J/\psi + \gamma$ production serves as a sensitive probe of photon-induced quarkonium production mechanisms. We thus present the corresponding event yields predicted for the HL-LHC and the FCC.