Ricerche di supersimmetria con il rivelatore ATLAS

The search for light supersymmetric partners of the top quark (stop squark) could result into the early discovery of physics beyond the Standard Model at the LHC. In this thesis, an analysis based on ATLAS simulated data is presented to study the possibility to discover scalar top quarks at the LHC. A benchmark model in the framework of the Minimal Supersymmetric Standard Model is considered, with a stop squark lighter than the top quark, yielding a final state similar to the one for $tar{t}$ production. We demonstrate that a significant excess of signal events can be extracted with 2 fb-1 of data obtained with the parametrized detector simulation. A technique to subtract the SM background based on the data is developed to achieve this result. The detailed detector simulation has also been used to study trigger and detector effects, confirming the possibility to subtract the background from the data.