Ricerca di particelle supersimmetriche nell'ambito dell'esperimento ATLAS

The first part of the thesis reports a phenomenological study of the supersymmetric models known as “MSUGRA”. Particular emphasis is given to the “Focus Point” choice of the parameters that characterizes the MSUGRA models. The Focus Point model features a description of the Dark Matter density in the Universe that is compatible with the WMAP experimental data. Furthermore this model can be easily studied using ATLAS data, starting from the very few years of data taking. My original contribution to this study has been the calculation of the invariant mass distribution of the leptons that characterize a particular decay of neutralinos. The invariant mass distribution has been studied as a function of the neutralino mass. In the final part of the thesis, simulated data have been used to study the possibility of neutralino decay discovery with the ATLAS detector. The background relevance has been analyzed, as well as the precision that can be achieved in the neutralino mass measurement. As a conclusion the limits that can be imposed on the MSUGRA parameters have been determined as a function of the neutralino mass.