Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in the $\tau_{e} \tau_{\mu}$ Decay Mode at $\sqrt{s}$ = 7 TeV with the ATLAS Detector

This thesis presents a search for neutral Higgs bosons (phi^0) of the Minimal Supersymmetric Standard Model (MSSM) in the decay mode phi^0 -> tau tau -> e mu + 4nu. The analysis uses a dataset that corresponds to an integrated luminosity of 4.7/fb of proton collision data collected with the ATLAS Experiment at the Large Hadron Collider (LHC) at a center–of–mass energy of 7 TeV. The search makes use of events with one reconstructed electron and one reconstructed muon in the final state. In the MSSM, neutral Higgs bosons are produced predominantly in gluon fusion events and in association with b-quarks. Events are therefore categorized according to the absence or presence of exactly one jet identified as stemming from a b-quark. The dominant backgrounds (Z/gamma^* -> tau tau -> e mu + 4nu, top quark pair production, and multi-jet events) are estimated using data-driven techniques. No significant excess is observed. Therefore, upper limits on the product of the production cross-section and the branching fraction to tau lepton pairs are given for hypothetical mass values between 90 and 300 GeV of a generic Higgs boson produced in either of the two production modes. The results are further interpreted in the mhmax scenario of the MSSM, and limits in the m_A–tan(beta) plane are set. Finally, the combined ATLAS search for phi^0 -> tau tau, which also takes other decay modes into account, is discussed.