Search for scalar leptons at LEP with the L3 detector

In this thesis, I present a search for scalar leptons in e+e- annihilation using the L3 detector at LEP. Data collected in 1999 and 2000, at center-of-mass energies between 192 GeV and 208 GeV, was used in this analysis. This work covered the scalar lepton searches in both SUGRA and GMSB models. To achieve this analysis, a parametrized selection was developed to handle the different event signatures in SUGRA models. Improvement of the L3 simulation and reconstruction program packages was carried out so that one can simulated the scalar leptons in GMSB models correctly. The simulation of the L3 Time Expansion Chamber (TEC) dE/dx measurement was rewritten to facilitate the analysis for a stable slepton signal, which is relevant in some parts of the parameter space in GMSB models. In this analysis, we didn't abserve any significant indication of scalar lepton production of any type. We achieved the following mass exclusion limits for scalar leptons in SUGRA models, for large dM: M(scalar e) > 97 GeV (expected 97 GeV) M(scalar mu) > 86 GeV (expected 86 GeV) M(scalar tau) > 78 GeV (expected 79 GeV) We achieved the following lifetime independent mass exclusion limits for scalar taus in GMSB modles: M(scalar tau) > 80 GeV (expected 79 GeV)