Discovery potential of mSUGRA-Supersymmetry in the $\mu$+Jet+MET channel at CMS

In this thesis a study is presented, investigating the discovery potential for supersymmetry in the μ+jets+ET channel during the early data taking of the CMS detector at LHC. Supersymmetry predicts a new particle for each one present in the standard model, differing in spin by half a unit. As these supersymmetric particles, called sparticles, have not been observed so far, this symmetry must be broken and the masses of the new particles must be higher than their standard model counterparts. Assuming the unification of masses and couplings at very high energies and the involvement of gravity in the breaking mechanism, minimal supergravity makes strong predictions about the mass spectrum, production mechanisms and decay channels of the sparticles. For most regions of the allowed parameter space, it predicts a decay of sparticles via a cascade to lighter particles, hence multiple jets and leptons are expected. Assuming conserved R-parity, at the end of the cascade a stable heavy particle, usually assumed to be the lightest neutralino, will escape undetected, resulting in large missing energy. The potential of separating such events from the standard model background in the CMS detector has been evaluated using the full detector simulation, taking into account the effects of systematic uncertainties. The separation has been carried out both by conventional rectangular cuts as well as using the multivariate analysis technique Boosted Decision Trees (BDTs). Some regions in the parameter space just beyond the existing limits from TEVATRON and LEP are shown to be observable within 100 pb−1 of integrated luminosity. Larger regions further away from existing limits are reachable within 1 fb−1. Regions with high sparticle masses generally need more integrated luminosity or better controlled systematics to be observed. The use of BDTs increases the discovery mass range, however they require strictly controlled systematic uncertainties.