Improved modeling of $\gamma\gamma$ processes in ultraperipheral collisions at hadron colliders

TL;DR

This paper introduces advanced theoretical models and an updated Monte Carlo generator for simulating gamma-gamma processes in ultraperipheral collisions at the LHC, enhancing accuracy and scope of photon-photon interaction studies.

Contribution

The paper presents new theoretical developments and updates to the gamma-UPC Monte Carlo generator, enabling detailed simulation of exclusive gamma-gamma processes in ultraperipheral collisions.

Findings

Implementation of azimuthal modulation calculations for dilepton pairs.

Prediction of neutron emission probabilities in photoexcited lead ions.

Comparison of simulation results with RHIC and LHC data shows improved agreement.

Abstract

The CERN LHC is not only the current energy-frontier collider for parton-parton collisions, but has proven a powerful photon collider providing photon-photon ($\gamma\gamma$) collisions at center-of-mass energies and luminosities never reached before. The latest theoretical developments implemented in the gamma-UPC Monte Carlo (MC) event generator, which can calculate arbitrary exclusive final state produced via $\gamma\gamma$ fusion in ultraperipheral collisions (UPCs) of protons and/or nuclei at the LHC, are presented. These include azimuthal modulations of dilepton pairs produced in the $\gamma\gamma\to\ell^+\ell^-$ process, and neutron emission probabilities for photoexcited lead ions in PbPb UPCs. A few comparisons of the results of the updated gamma-UPC v.1.6 code to relevant RHIC and LHC data are presented.