Abstract

Abstract The results of a search for charged Higgs bosons are presented. The analysis is based on 4.6fb−1 of proton-proton collision data at $ \sqrt {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 abquarkandachargedHiggsbosonbetween5%and1%forchargedHiggsbosonmasses ranging from 90 GeV to 160 GeV, respectively. In the context of the $ m_h^{\max } $ 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.

Highlights

  • Charged Higgs bosons (H+, H−) are predicted by several non-minimal Higgs scenarios, such as Two Higgs Doublet Models (2HDM) [1] or models containing Higgs triplets [2,3,4,5,6]

  • This paper describes a search for charged Higgs bosons with masses in the range 90– 160 GeV, using ttevents with a leptonically or hadronically decaying τ lepton in the final state, i.e. with the topology shown in figure 1

  • In order to predict the background for the charged Higgs boson search, the measured jet → τ misidentification probability is applied to simulated tt, single top quark, W +jets, Z/γ∗+jets and diboson events, all of which are required to pass the full event selection except for the τ identification

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Summary

Introduction

Charged Higgs bosons (H+, H−) are predicted by several non-minimal Higgs scenarios, such as Two Higgs Doublet Models (2HDM) [1] or models containing Higgs triplets [2,3,4,5,6]. In a type-II 2HDM, such as the Higgs sector of the Minimal Supersymmetric extension of the Standard Model (MSSM) [7,8,9,10,11], the main H+ production mode at the Large Hadron Collider (LHC) is through top quark decays t → bH+, for charged Higgs boson masses (mH+) smaller than the top quark mass (mtop). B(H+ → τ ν) = 100% is assumed, unless otherwise specified Under this assumption, the combined LEP lower limit for the charged Higgs boson mass is about 90 GeV [13]. This paper describes a search for charged Higgs bosons with masses in the range 90– 160 GeV, using ttevents with a leptonically or hadronically decaying τ lepton in the final state, i.e. with the topology shown in figure 1.

Data and simulated events
Electrons
Removal of geometric overlaps between objects
Missing transverse momentum
Event selection
Data-driven estimation of backgrounds with misidentified leptons
Reconstruction of discriminating variables after the selection cuts
Backgrounds with electrons and jets misidentified as τ jets
Event yields and ETmiss distribution after the selection cuts
Data-driven estimation of the multi-jet background
Data-driven estimation of backgrounds with correctly reconstructed τ jets
Event yields and mT distribution after the selection cuts
Systematic uncertainties arising from the detector simulation
Systematic uncertainties arising from the generation of ttevents
Systematic uncertainties arising from data-driven background estimates
Results
Conclusions
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