Photon-photon collisions at the LHC

by Dr Lucian Harland-Lang (UCL)

Friday 17 Apr 2026, 13:00 → 14:00 Europe/London

Bohr Conference Room

LHC collisions can act as a source of photons in the initial state, in addition to the more standard quark and gluon-initiated processes. Indeed, photon-initiated production is a promising search channel for BSM states as well as probe of the EW couplings of the SM particles. Due to the colour singlet nature of the photon, a key feature of this process in proton-proton collisions is the possibility for leaving the protons intact and/or producing rapidity gaps in the final state. Moreover, the possibilities are not limited to proton collisions: in heavy ion collisions, the ions can act as a strong source of photon radiation, and the photon-initiated channel can play a significant role.

In this talk I will overview the current status and prospects for photon-initiated production at the LHC, and discuss some recent developments in the field, from coincident particle production to ion excitations and their role in rapidity gap vetos. I will discuss the theoretical foundations underlying the modelling of such processes and their implementation in the SuperChic Monte-Carlo event generator. I will in particular motivate why we are justified in viewing such processes as being due to photon-photon (as opposed to hadron-hadron) collisions, even if the devil is as always in the detail.