Search for supersymmetric particles in final states with jets and missing energy with the ATLAS Experiment at the LHC

With the start of the Large Hadron Collider (LHC) at CERN it is now possible to study physics at the TeV-scale for the first time. At this unprecedented energy range it is expected that the Standard Model of particle physics will reach its limits and new phenomena can appear. One of the main goals of the ATLAS experiment is the search for physics beyond the Standard Model. This includes observing supersymmetric particles, which are predicted to have masses of several hundred GeV up to a few TeV. The subject of this thesis is the search for supersymmetric particles in final states with jets and missing transverse energy and the evaluation of the ATLAS discovery potential for supersymmetric particles in the Minimal Supersymmetric Standard Model (MSSM) parameter space for these channels. Different centre-of-mass energies of sqrt(s) = 14 TeV, 10 TeV and 7 TeV are assumed. For many R-parity conserving SUSY models, the decay of supersymmetric particles leads to detector signatures characterized by missing transverse energy and multi-jets, sometimes accompanied by leptons. In this thesis, SUSY searches with >= 2 - 6 jets and 0 - 2 leptons (electrons, muons) are studied, with a focus on 0-lepton channels, that are expected to be sensitive in large areas of the SUSY parameter space. The search strategies for supersymmetric particles are applied on a sets of differently constrained SUSY models and on several hundred SUSY signals, generated within the pMSSM subspace of the MSSM. The goal of this work is to explore the reach of the performed SUSY searches for completely different decay signatures. It will be shown that the ATLAS SUSY searches cover a large parameter space of SUSY models. The first p-p collisions at a centre-of-mass energy of sqrt(s) = 7 TeV in March 2010 allow a compaison of the measured data with the Monte Carlo predictions, in order to see how well the detector response is understood in the context of SUSY specific variables used in the 0-lepton analyzes. All measurements are found to be in agreement with the Standard Model expectations within the associated systematic uncertainties. The results indicate that the ATLAS SUSY searches cover a large parameter space and it is possible to discover or exclude some SUSY models already with a few pb-1 of integrated luminosity.