A Sensitivity Study for Higgs Boson Production in Vector Boson Fusion in the <em>H → ττ →lh + 3ν</em> Final State with ATLAS

Abstract

For a hypothetical Higgs boson mass between 114.4GeV and about 135GeV the production by Vector Boson Fusion and the decay <em>H → ττ →lh + 3ν</em> is one of the most promising discovery channels at the LHC. In this thesis, a study of the expected sensitivity of the ATLAS detector for this channel at a centreof- mass energy of 14 TeV is presented. For the first time, this study includes a full treatment of additional proton-proton interactions, so-called pile-up. The presence of pile-up significantly affects the signal selection efficiency and leads to a deterioration of the reconstructed Higgs boson mass, which is used as a discriminating observable. Two methods have been developed to estimate the dominant background processes from data. By replacing the muons in <em>Z → μμ</em> events with simulated <em>τ</em> lepton decays, Z <em>→ ττ</em> events can be modelled with high precision. The non-resonant background, t¯t production and W + jets, is estimated by selecting events where lepton and hadronic <em>τ</em> decay have the same electric charge. Assuming a dataset corresponding to an integrated luminosity of 30 fb⁻¹, an expected signal significance between 3.0<em>σ</em> and 4.4<em>σ</em> is obtained for a Higgs boson mass between 115GeV and 135GeV. The expected significance decreases to 1.6–2.0<em>σ</em> in the presence of pile-up.