Searches for Higgs bosons in the di-tau decay channels at the ATLAS experiment

The search for the Higgs boson will be one of the primary tasks of the LHC. One of the most promising channels in the search for a low mass Higgs boson will be the scenario where the Higgs is produced via Vector Boson Fusion and subsequently decays to a pair of tau leptons. One of the dominant (and most complex) backgrounds to this analysis is expected to come from tt decays. Monte Carlo samples with a centre-of-mass energy of 14 TeV are used to investigate the contributions from different tt decay modes and to develop methods to reduce the contribution from this background process and improve the overall sensitivity of the analysis. A technique to estimate contributions from background processes when there are insufficient Monte Carlo samples available to calculate this directly is also presented. A low mass Standard Model Higgs boson will require at least 10 inverse femtobarns of data before a discovery (or exclusion) can be claimed, but extensions to the Standard Model that realise Supersymmetry predict that there should be three neutral Higgs bosons. The production cross-section is strongly enhanced and it is there- fore expected that competitive limits on an MSSM Higgs boson can be made using data from the 2010-2011 LHC data-taking period (1 inverse femtobarn expected with 7 TeV centre-of-mass collisions). A search strategy for an MSSM Higgs boson decaying to two taus is presented, focusing on ensuring analysis robustness during this early period. Comparisons with the first ATLAS data are also made.EThOS - Electronic Theses Online ServiceGBUnited Kingdo