Search for Trilepton Events in the ATLAS experiment at the LHC with 2 fb$^{-1}$ at $_sqrt{s}$=7 TeV

In order to observe new physics phenomena like Supersymmetry (SUSY), one needs clean decay channels to distinguish them from the background. A promising channel are three isolated leptons in the final state. Therefore a search for trilepton events is performed with 2 fb$^{-1}$ of data at $sqrt{s}$ = 7 TeV provided by the ATLAS experiment. No specific SUSY model is considered in the analysis, but a phenomenologic model using masses of gluinos and squark to build a two-dimensional grid. No excess in data has been observed and confidence level been set to the grid points. To validate the modelling of fake and secondary leptons in Monte Carlo samples, a data-driven method - the so called matrix method - is used to determine the event yield of processes without three leptons from the hard scattering. Within the uncertainties, the event yields from Monte Carlo and the matrix method agree.