Observation of Wγγ triboson production in proton-proton collisions at √s = 13 TeV with the ATLAS detector

Abstract

This letter reports the observation of W(lv)γγ production in proton-proton collisions. This measurement uses the full Run 2 sample of events recorded at a center-of-mass energy of √s = 13 TeV by the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb−1. Events with a leptonically-decaying W boson and at least two photons are considered. The background-only hypothesis is rejected with an observed and expected significance of 5.6 standard deviations. The inclusive fiducial production cross section of W(ev)γγ and W(µv)γγ events is measured to be σfid = 13.8 ± 1.1(stat)+2.1−2.0(syst) ± 0.1(lumi) fb, in agreement with the Standard Model prediction.