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.