A feasibility study into the measurement of W and Z cross sections with the ATLAS detector

In 2009 the Large Hadron Collider at CERN in Geneva, Switzerland, is expected to start colliding head on two proton beams at 7 (to be increased to 14) TeV centre of mass energy. ATLAS is a general purpose detector built to monitor the resultant activity from LHC collisions. ATLAS and the LHC will facilitate a precise measurement of W and Z boson production cross sections and their ratio R. In first data W and Z events may be used as `standard candle events' to understand detector performance, and are interesting in their own right as they are a powerful tool to test and constrain further the Standard Model. Any significant deviation from the predicted behaviour of these events could be one of the first indications of physics beyond the Standard Model, and so understanding these events is of paramount importance to new physics searches. It is important, whenever possible, not to rely on Monte Carlo simulation when measuring the above (or indeed any) quantities. This analysis proposes methods of understanding the detector response and efficiency from data using Z->ll events, as well as techniques to fold in such quantities to measure W and Z cross sections (with the branching ratio for decay in the electron channel) and R along with their predicted uncertainties for an early data scenario (100pb^1).