The Search for Evidence of Supersymmetry in Trilepton Final States at the LHC

The potential of the ATLAS detector to discover trilepton final state signatures from decays of supersymmetric particles at the LHC is investigated. An inclusive and an exclusive trilepton search have been conducted for a range of different mSUGRA scenarios, in the focus point region, in the bulk region, and at the edge of the current experimental limits on SUSY. The inclusive trilepton plus high transverse momentum jet final state is found to be a clean, simple and robust signature, with a discovery potential of between a few hundred inverse picobarns to a few inverse femtobarns of data, depending on the SUSY scenario considered. The inclusive trilepton channel has the potential to be an excellent candidate for an early physics programme at the LHC. In contrast, an analysis strategy has also been developed for the hadronically quiet trilepton channel from direct gaugino production. Optimised for the focus point region, the exclusive selection relies on stringent lepton track isolation and also includes cuts on variables such as transverse missing energy and on the hadronic activity in the event. This exclusive trilepton channel could yield a discovery with a few tens of inverse femtobarns of data if strongly interacting sparticles are not produced abundantly at the LHC. Studies have been conducted into the expected performance of the ATLAS detector and trigger, in addition to possible data-driven methods to estimate the Standa rd Model backgrounds to the trilepton signal.