Observation of WWγ Production and Search for Hγ Production in Proton-Proton Collisions at SQUARE ROOT s=13 TeV

Abstract

The observation of WW gamma production in proton -proton collisions at a center -of -mass energy of 13 TeV with an integrated luminosity of 138 fb-1 is presented. The observed (expected) significance is 5.6 (5.1) standard deviations. Events are selected by requiring exactly two leptons (one electron and one muon) of opposite charge, moderate missing transverse momentum, and a photon. The measured fiducial cross section for WW gamma is 5.9 +/- 0.8(stat) +/- 0.8(syst) +/- 0.7(modeling) fb, in agreement with the next -to -leading order quantum chromodynamics prediction. The analysis is extended with a search for the associated production of the Higgs boson and a photon, which is generated by a coupling of the Higgs boson to light quarks. The result is used to constrain the Higgs boson couplings to light quarks.