Optimisation of searches for supersymmetry with the ATLAS detector

The ATLAS experiment is one of the four large experiments at the Large Hadron Collider which is specically designed to search for the Higgs boson and physics beyond the Standard Model. The aim of this thesis is the optimisation of searches for Supersymmetry in decays with two leptons and missing transverse energy in the nal state. Two dierent optimisation studies have been performed for two important analysis aspects: The nal signal region selection and the choice of the trigger selection. In the rst part of the analysis, a cut-based optimisation of signal regions is performed, maximising the signal for a minimal background contamination. By this, the signal yield can in parts be more than doubled. The second approach is to introduce di-lepton triggers which allow to lower the lepton transverse momentum threshold, thus enhancing the number of selected signal events signicantly. The signal region optimisation was considered for the choice of the nal event selection in the ATLAS di-lepton analyses [1, 2]. The trigger study contributed to the incorporation of di-lepton triggers to the ATLAS trigger menu.