Studien zur Unterdrückung von Untergrundprozessen in Zerfällen des supersymmetrischen Top-Squark in ein Top-Quark und ein Neutralino

In this bachelor thesis techniques to suppress the background in the search for the decay of a top quark superpartner into a top quark and a neutralino are analysed. For the search for supersymmetry at the ATLAS experiment at the LHC it is important to suppress the background of these decays. This is possible, if differences between the decay of the top quark superpartner and the background processes are found. In an analysis with Monte-Carlo simulated data, differences in the following distributions were found: The transverse $t\bar t$-momentum, the perpendicular component of the missing transverse momentum with respect to the leptonic top quark and the angles $\Delta\varphi$, as well as $\cos\theta$ between the top quarks. In addition, efficiency and purity for cuts on these observables were analysed. The best way to differentiate between signal and background was found to be by cuts on the transverse momentum of the $t\bar t$-system and the perpendicular component of the missing transverse momentum.