Search for SUSY trilepton events with ATLAS at the LHC

One of the best motivated extension of the Standard Model is SUper-SYmmetry (SUSY). The ATLAS experiment at the pp-collider LHC will search for the new particles predicted by SUSY. In this talk, the discovery potential of the direct production of charginos and neutralinos decaying into a final state with three charged leptons is presented. In the start-up phase of the LHC an important signal of SUSY, the missing transverse energy, will need extensive calibration studies. We therefore present an analysis which does not rely on this signature. The model used for the analysis is mSUGRA. A full simulation of the ATLS detector has been used, and the most important backgrounds tt, W± Z and ZZ have been taken into account. (orig.)