Estimation of standard model backgrounds to the search for electroweak production of supersymmetry in events with at least two tau leptons in the final state

This thesis presents a search for Supersymmetry in events with at least two hadronically decaying tau leptons and missing transverse energy. The ana\-lysis is focused on the electro-weak production of gaugino pairs. Electroweak production processes for SUSY particles are promising candidates for the discovery of Supersymmetry with $R$-parity conservation at hadron-hadron colliders. For the analysis a sample of proton-proton collisions at a center of mass energy of $\sqrt{s}=\unit[8]{TeV}$ with an integrated luminosity of $\int {\cal L}~\mathrm{dt}= \unit[20.3]{fb^{-1}}$ is used. The collisions have been recorded with the ATLAS detector at the LHC in the year 2012. In two different selections the Standard Model predictions are compared with the observations. The observation of 6 events in the first selection and 14 in the second does not deviate significantly from the Standard Model with an expectation of 11 events in the first selection and 17 in the second. These results are interpreted in a phenomenological Minimal Supersymmetric Standard Model and in simplified models. For a simplified model with a chargino-neutralino pair production scenario the parameter space for masses of the lightest neutralino up to $\unit[100]{GeV}$ and up to $\unit[350]{GeV}$ for the lightest chargino mass can be excluded. For a simplified model with chargino pair production processes the parameter space for the lightest neutralino mass up to $30-\unit[50]{GeV}$ in a range for the lightest chargino mass of $170-\unit[330]{GeV}$ can be excluded. This thesis is focused on the estimation techniques of Standard Model background processes. Different methods for the estimation of the background originating from $Z$-boson and top-quark decays are investigated.