ATLAS Collab.
Observation of Wγγ triboson production in proton-proton collisions at √s=13 TeV with the ATLAS detector
This letter reports the observation of W(ℓν)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, corresponding to the observation of this process. The inclusive fiducial production cross section of W(eν)γγ and W(μν)γγ events is measured to be σfid=12.2 ± 1.0(stat) +1.9−1.8(syst) ± 0.1(lumi) fb, in agreement with the Standard Model prediction.