Measurement of coherent exclusive J/ψ→μ⁺ μ^-photoproduction in ultraperipheral OO Collision at LHC with √s_NN=5.36TeV with the CMS Detector

Ultra-peripheral collisions (UPCs) at the Large Hadron Collider (LHC) enable the study of photon-induced interactions in the strong electromagnetic fields generated by highly relativistic nuclei. In these collisions, where the impact parameter exceeds twice the nuclear radius, a quasi-real photon from one nucleus can interact with the other nucleus either coherently (with the entire nucleus) or incoherently (with individual nucleons), producing vector mesons such as the J/ψ. These processes serve as sensitive probes of the gluon distribution and nuclear structure at small Bjorken x.

In this work, we present a measurement of the differential cross section for coherent J/ψ photoproduction in ultra-peripheral oxygen-oxygen (O--O) collisions at a nucleon-nucleon center-of-mass energy of √s_NN = 5.36TeV, using data collected with the CMS detector. To isolate the exclusive coherent signal, we remove hadronic pileup contributions and extract the J/ψ signal through invariant mass reconstruction. The resulting distributions are compared with Monte Carlo simulations using STARlight for the coherent signal and HIJING for pileup modeling. We compare the differential cross section with respect to rapidity with theoretical predictions and results from previous experiments.