Tau lepton reconstruction with energy flow and the search for R-parity violating supersymmetry at the ATLAS experiment

This thesis investigates the discovery potential of the ATLAS experiment at the Large Hadron Collider (LHC) for $R$-parity violating (RPV) supersymmetric (SUSY) models in the framework of mSUGRA, where the stau ($\tilde\tau$) is the lightest supersymmetric particle (LSP). Hence, the LSP is charged and decays in contrast to $R$-parity conserving models. For the first time in the framework of this RPV model a detailed signal to background analysis is performed for a specific benchmark scenario using a full Monte Carlo simulation of the ATLAS detector. Furthermore a feasibility study for an estimate of the stau LSP mass is given. The fast track simulation FATRAS is a new approach for the Monte Carlo simulation of particles in the tracking systems of the ATLAS experiment. Its results are compared to first data at $\sqrt{s}=900GeV$. Additionally, two generic detector simulations are compared to the full simulation of the ATLAS detector. The reconstruction of tau leptons is crucial for many searches for new physics with ATLAS. Therefore, the reconstruction of tracks for particles from tau decays is studied. A novel method, PanTau, is presented for the tau reconstruction in ATLAS. It is based on the energy flow algorithm eflowRec. Its performance is evaluated in Monte Carlo simulations. The dependency of the identification variables on the jet energy are studied in detail. Finally, the energy flow quantities and the identification variables are compared between Monte Carlo simulations and measured multijet events with first ATLAS data at $\sqrt{s}=7TeV$.