Photoproduction at RHIC and the LHC

TL;DR

Heavy-ion colliders like RHIC and LHC utilize intense electromagnetic fields to explore photonuclear and two-photon interactions, enabling studies of meson production, gluon distributions, and potential new physics at unprecedented energies.

Contribution

This paper reviews recent experimental results from RHIC and discusses future prospects for photoproduction studies at the LHC, highlighting the potential for new physics and low-x gluon measurements.

Findings

RHIC has observed coherent photoproduction of various particles.

Photoproduction studies demonstrate unique symmetric final states.

LHC will enable exploration of gluon saturation and new physics.

Abstract

The strong electromagnetic fields carried by relativistic highly charged ions make heavy-ion colliders attractive places to study photonuclear interactions and two-photon interactions. At RHIC, three experiments have studied coherent photoproduction of $\rho^0$, 4$\pi$, $J/\psi$, $e^+e^-$ pairs, and $e^+e^-$ pairs where the electron is bound to one of the incident nuclei. These results show that photoproduction studies are possible, and demonstrate some of the unique possibilities due to the symmetric final states and the ion targets. The LHC will reach photon-nucleon energies many times higher than at HERA; these collisions can be used to measure the gluon distributions in nuclei at very low Bjorken$-x$, where shadowing and gluon saturation may become important; LHC $\gamma\gamma$ collisions may also be attractive places to search for some types of new physics. ATLAS, CMS and ALICE are all planning to study photoproduction. After introducing the principles of photoproduction at hadron colliders, I will review recent results from RHIC on meson and $e^+e^-$ production, and then discuss prospects for studies at the LHC.