Optimisation of the search for MSSM Higgs Bosons in the decay channel $A/H/h \rightarrow \tau^+\tau^- \rightarrow \mu + \tau_{had} + \nu_\mu + 2 \nu_\tau$ with the ATLAS detector

The optimisation of the search for the neutral MSSM Higgs bosons in the decay channel $A/H/h \rightarrow \tau^+\tau^- \rightarrow \mu + \tau_{had} + \nu_\mu + 2 \nu_\tau$ with the ATLAS detector is presented. The ATLAS data of the data taking period in 2011 at $\sqrt{s} = 7$\,TeV with an overall integrated luminosity of $L_{\text{int}} = 4.7$\,$\text{fb}^{-1}$ is used. For the optimisation, multivariate methods such as Boosted Decision Trees and Likelihood Estimators were trained against two of the major backgrounds in this decay channel, the $W+$jets background and the QCD background. The training was carried out separately for both backgrounds using a potential signal at $m_A = 120$\,GeV and $\text{tan}\beta = 20$ within the $m_h^{\text{max}}$ benchmark scenario. The Boosted Decision Trees were found to give the best performance in both cases. An overall background rejection of $57.9$\,\% was achieved and the $\frac{s}{\sqrt{b}}$ significance for the given working point was improved by $8.1$\,\% to $4.36$.