Studying WWγ and WZγ production in proton–proton collisions at √s = 8 TeV with the ATLAS experiment

Quartic gauge couplings are tested by this study of the production of WWγ and WZγ events in 20.2 fb−1 of proton–proton collisions at a centre-of-mass energy of √s = 8 TeV recorded with the ATLAS detector at the LHC. The final state of WWγ events containing an electron, a muon and a photon is analysed as well as the final states of WWγ and WZγ production containing an electron or a muon, two jets and a photon. For all final states two different fiducial regions are defined: one yielding the best sensitivity to the production cross-section of the process and one optimised for the detection of new physical phenomena. In the former region, the W W γ production cross-section is computed and in both regions, upper limits on the W W γ and W Zγ production cross-section are derived. The results obtained in the second phase space are combined for the interpretation in the context of anomalous quartic gauge couplings using an effective field theory.