Search For A Heavy Particle Decaying Into Electron-muon In Pp Collisions At (?)=7TeV At LHC With The ATLAS Detector

In this thesis, a search for eμ resonance of τ sneutrino (vτ) decay using pp collision data of (?)=7TeV collected by the ATLAS experiment at LHC is described. The Standard Model (SM) processes having electron and muon in the final state are estimated with Monte Carlo simulations. A matrix method was used to estimate the jet fake background. We first analysed the35pb-1data taken in2010from March to December and later updated the results with1.07fb-1data taken in2011from March2011to June2011. Seeing no signifi-cance deviation of data from the SM prediction, we set the limit on the τ sneutrino mass and also the limit of coupling parameter as function of vτ mass.τ sneutrino of m<1.32TeV is excludes assuming the coupling parameters λ312=0.05and λ311’=0.10. The limit observed surpasses the results reported by the Tevatron experiments. The limits on the coupling pa-rameters are the best results to date for msnt>275GeV. The limits on the production cross section of τ sneutrino can also be interpreted to other models predicting a heavy particle decaying to electron and muon pair.