Observation of the Higgs Boson Decaying to WW to leptons and neutrinos

Abstract

The search for the Higgs boson produced through gluon fusion and vector boson fusion and decaying to WW bosons is performed. The WW bosons subsequently decay to combinations of electrons, muons and neutrinos. The final states are accompanied by up to two jets. The search is performed using 25 fb-1 of data collected by the ATLAS detector in sqrt(s) = 7 TeV and sqrt(s) = 8 TeV proton-proton collisions at the LHC. Comparing the collected data to Standard Model expectations, in which the Higgs boson is assumed to not exist, yields a 6.1 sigma excess at around a mass of 130 GeV and over a wide mass range. The significance is the same for a mass of 125.36 GeV, which is the Higgs mass determined by the Higgs decaying to photon and Z boson searches. The vector boson fusion production process is observed with a significance of 3.2 sigma at a mass of 125.36 GeV. The ratio of the expected to the observed values of the total production cross section times branching ratio is 1.08 (+0.22,-0.20) at a Higgs boson mass of 125.36 GeV. When separated by Higgs production modes, this value is 1.01 (+0.27, -0.25) for gluon fusion, and 1.27 (+0.53, -0.45) for vector boson fusion. The total cross sections for the gluon fusion and vector boson fusion processes are measured. The fiducial cross section for the gluon fusion process is measured in final states containing zero and one associated jets