Investigation of the High Mass Drell Yan Spectrum with ATLAS

The Large Hadron Collider started data taking at the end of 009 and an integrated luminosity of 1 fb^-1 is hoped for by the end of 2011. A precise measurement of the high mass Drell Yan spectrum offers a good opportunity for a model independent search for new physics. The muon channel is well suited for this, due to the clean signature and the good muon identification in the Muon Spectrometer. Previous studies at high dimuon masses neglected all background contributions. This study investigated the impact of background on the Drell Yan spectrum and it was found that top antitop decays are the most important contribution. Various selection cuts to suppress those background contributions were studied. A method to take systematic uncertainties into account, whilst optimising these selection cuts, has been developed. It was shown that two additional selection cuts based on b-tagging and Missing Transverse Energy (MET) will reduce the overall uncertainty for a bin from 200 GeV to 300 GeV from 19.1% to 17.2% for an integrated luminosity of 50 pb^-1. An important aspect of this analysis is to ensure that the efficiency for all selection cuts remains stable at very high dimuon masses of up to 1 TeV. This is not the case for the conventional MET, so a derived variable has been introduced and tested.