The proton beam collisions occurring at LHC in CERN result in a scarce interaction of two photons irradiated from colliding protons. These cases represent a valuable tool for the study of electroweak interactions. For instance, in processes with a pair production of yy → WW intermediate bosons, they enable a high accuracy determination of a quartic coupling between a photon and a W boson. The measurement of the yy → μμ muon pair production is an important milestone on this journey. It proves that we are able to identify two-photon processes against a giant background and serves as a benchmark to make comparisons with theoretical models.
Measurement of the exclusive γγ → μ+μ− process in proton–proton collisions at 13 TeV recorded with the ATLAS detector