The Event-Mixing Technique for Modeling the $\text{t}\bar{\text{t}}$ Background in a Search for Supersymmetry in the Di-Lepton Channel

In this thesis a search for Supersymmetry in the opposite-sign same-flavor di-lepton channelis presented. Data recorded by the CMS detector at the LHC accelerator corresponding to anintegrated luminosity of 12.2 fb−1 at a center-of-mass energy of 8 TeV is analyzed. Events withat least two muons or two electrons with opposite charge, a significant transverse momentumimbalance, and at least one or at least two jets are selected. Supersymmetric particle decays areexpected to form an edge-like structure in the di-lepton mass spectrum. The main backgroundfrom Standard-Model processes is t¯ pair production. This background is estimated in a datatdriven way using the event-mixing technique. Since event mixing is novel to estimate t¯ events,tthe method is validated in detail.In the analyzed data no significant excess w. r. t. the event-mixing prediction is observed. In acounting experiment as well as in a fit of the shape of the distribution the data is in agreementwith the expectations from the Standard Model. Hence, exclusion limits are calculated in termsof number of events forming an edge in the di-lepton mass spectrum. Additionally, the resultsare interpreted within a simplified model spectrum, assuming direct gaugino production anda decay chain like χ0 → ˜± → χ0 + − . Limits are set on the masses of the supersymmetric˜2˜1particles.