The Study Of WZ Boson Pair Production With Fully Leptonic Final States With The ATLAS Detector

Searches for diboson resonances provide an essential test of theories of electroweak symmetry breaking beyond the Standard Model(BSM).In this paper,a search for a heavy resonance decaying into WZ in the fully leptonic channel(electrons and muons)is performed based on proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a centre-of-mass energy of 13 TeV.Two benchmark models,heavy vector triplet(H VT)and Georgi-Machacek(GM)model,are considered for the interpretation of possible resonant signals.For the first-round analysis corresponding to an integrated luminosity of 36.1 fb-1,using real and simulated data in the dedicated signal regions with estimated real and fake backgrounds and all related uncertainties,a likelihood-based signal strength extraction is performed.No significant excess is observed over the Standard Model predictions and limits are set on the production cross section times branching ratio of a heavy vector particle produced either in quark-antiquark fusion or through vector-boson fusion.No evidence of heavy resonance production is found for masses below2260(2460)GeV.Constraints are also obtained on the mass and couplings of a singly charged Higgs boson,in the GM model,produced through vector-boson fusion.The results show a local excess of events over the Standard Model expectations at a resonance mass of around 450 GeV.The local significances for signals of GM model and of a HVT model are 2.9 and 3.1 standard deviations respectively.A second-round analysis exploiting the full Run-? ATLAS data is ongoing with similar analysis strategy but larger statistics.An Aritfial Neural Network based signal selection strategy is implemented to improve the signal sensitivity.The result will also be interpreted as a measurement of fraction of differently polarized WZ interactions in standard model.