Search for a high-mass Higgs boson decaying to a W boson pair in pp collisions at √ s = 8 TeV with the ATLAS detector

A search for a high-mass Higgs boson H is performed in the H→WW→ℓνℓν and H→WW→ℓνqq decay channels, using pp collision data corresponding to an integrated luminosity of 20.3 fb−1, collected at s√= 8 TeV by the ATLAS detector at the Large Hadron Collider. No evidence of a high-mass Higgs boson is found. Limits on σH×BR(H→WW) as a function of the Higgs boson mass mH are determined in three different scenarios: one in which the heavy Higgs boson has a narrow width compared to the experimental resolution, one a width increasing with the boson mass and modeled by the complex-pole scheme following the same behavior as in the Standard Model, and one for intermediate widths. The upper range of the search is mH=1500 GeV for the narrow-width scenario and mH=1000 GeV for the other two scenarios. The lower edge of the search range is 200−300 GeV and depends on the analysis channel and search scenario. For each scenario, individual and combined limits from the two WW decay channels are presented. At mH=1500 GeV, the highest mass point tested, σH⋅BR(H→WW) for a narrow-width Higgs boson is constrained to be less than 22 fb and 6.6 fb at the 95% CL for the gluon fusion and vector-boson fusion production modes, respectively.