Search For Heavy Resonances In The X?WW?ev?v Channel With The ATLAS Detector At The LHC

A search for a heavy neutral resonance X is performed in the X? WW?ev?v decay channel using pp collision data corresponding to an integrated lumi-nosity of 36.1 fb-1,collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider.The resonance can be either a heavy scalar Higgs boson or other heavy resonances with different spins.Two scenarios are considered for the heavy Higgs boson hypothesis with different decay widths in both the gluon-gluon fusion and the vector-boson fusion production modes,namely a narrow-width approximation and a large width assumption.Several hy-potheses are used for the interpretation to search for other resonances,like two Higgs doublet models,Georgi-Machacek model,heavy vector triplet model in the quark-antiquark annihilation mode,a bulk Randall-Sundrum graviton model with a spin-2 Graviton with a curvature scale parameter k/MPI of either 1 or 0.5 and a spin-2 signal in the vector-boson fusion mode.Three orthogonal event categories are defined in the analysis:two vector-boson fusion categories which are optimised for the signals produced in the vector-boson fusion mode with one jet or at least two jets and one quasi-inclusive gluon-gluon fusion category where the vector-boson fusion phase spaces defined by the two vector-boson fusion categories are excluded.No significant excess of events beyond the Standard Model background prediction is found in the mass range between 200 GeV and up to 5 TeV.Upper limits are set on the product of the production cross section of the resonange and the X ?? WW branching fraction.For heavy Higgs boson signals,values above 6.4 pb and 1.3 pb at mH = 200 GeV and above 0.008 pb and 0.005 pb at 4 TeV are excluded at 95%confidence level for the gluon-gluon fusion and the vector-boson fusion production modes,respectively.For signals predicted by the heavy vector triplet model,mass values below 1.3 TeV are excluded.Similarly,for signals pre-dicted by the bulk Randall-Sundrum graviton model,mass values below 1.1 TeV and 850 GeV are excluded for k/MPI = 1 and k/(?)PI = 0.5,respectively.