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

A search for a high-mass Higgs boson H is performed in the H?WW?l?l? and H?WW?l?qq decay channels using pp collision data corresponding to an integrated luminosity of 20.3 fb-1 collected at sqrt(s) = 8 TeV by the ATLAS detector at the Large Hadron Collider. No evidence of a high-mass Higgs boson is found. Limits on sH×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 for 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 signal interpretation, individual and combined limits from the two WW decay channels are presented. At mH=1500 GeV, the highest-mass point tested, sH×BR(H?WW) for a narrow-width Higgs boson is constrained to be less than 21 fb and 6.0 fb at 95% CL for the gluon fusion and vector-boson fusion production modes, respectively.