Search for charged Higgs bosons decaying via H ± → τν in $ t\overline t $ events using pp collision data at $ \sqrt {s} = 7\;TeV $ with the ATLAS detector

Abstract

Search for charged Higgs bosons decaying via H ± → τ ν in tt events using pp collision data at √ s = 7 TeV with the ATLAS detectorThe ATLAS collaboration E-mail: atlas.publications@cern.ch Abstract:The results of a search for charged Higgs bosons are presented. The analysis is based on 4.6 fb −1 of proton-proton collision data at √ s = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider, using top quark pair events with a τ lepton in the final state. The data are consistent with the expected background from Standard Model processes. Assuming that the branching ratio of the charged Higgs boson to a τ lepton and a neutrino is 100%, this leads to upper limits on the branching ratio of top quark decays to a b quark and a charged Higgs boson between 5% and 1% for charged Higgs boson masses ranging from 90 GeV to 160 GeV, respectively. In the context of the m max h scenario of the MSSM, tan β above 12-26, as well as between 1 and 2-6, can be excluded for charged Higgs boson masses between 90 GeV and 150 GeV. Keywords: Hadron-Hadron ScatteringOpen Access, Copyright CERN, for the benefit of the ATLAS collaboration This paper describes a search for charged Higgs bosons with masses in the range 90-160 GeV, using tt events with a leptonically or hadronically decaying τ lepton in the final state, i.e. with the topology shown in figure 1. Charged Higgs bosons are searched for in a model-independent way, hence exclusion limits are given in terms of B(t → bH + ), as well as in the m max • lepton+jets: tt → bbW H + → bb(qq ′ )(τ lep ν), i.e. W decays hadronically and τ decays into an electron or a muon, with two neutrinos;• τ +lepton: tt → bbW H + → bb(lν)(τ had ν), i.e. W decays leptonically (with l = e, µ) and τ decays hadronically;• τ +jets: tt → bbW H + → bb(qq ′ )(τ had ν), i.e. both W and τ decay hadronically.In section 2, the data and simulated samples used in this analysis are described. In section 3, the reconstruction of physics objects in ATLAS is discussed. Sections 4-6 present results obtained in the lepton+jets, τ +lepton and τ +jets channels, respectively. Systematic uncertainties are discussed in section 7, before exclusion limits in terms of B(t → bH + ) and tan β are presented in section 8. Finally, a summary is given in section 9.1 In the following, charged Higgs bosons are denoted H + , with the charge-conjugate H − always implied. Hence, τ denotes a positively charged τ lepton. Data and simulated eventsThe ATLAS detector [17] consists of an inner tracking detector with a coverage in pseudorapidity 2 up to |η| = 2.5, surrounded by a thin 2 T superconducting solenoid, a calorimeter system extending up to |η| = 4.9 for the detection of electrons, photons and hadronic jets, and a large muon spectrometer extending up to |η| = 2.7 that measures the deflection of muon tracks in the field of three superconducting toroid magnets. A three-level trigger system is used. The first level trigger is implemented in hardware, using a subset of detector information to reduce the event rate to a design value...

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