Event-by-Event Estimate of Muon Energy Loss in ATLAS

The ATLAS Muon Spectrometer is designed to provide efficient and precise stand-alone momentum measurement for muons of momentum up to O(1 TeV/c). The fluctuations of the muon energy loss in the material upstream of the Muon Spectrometer could deteriorate the physics performance, which requires the momentum to be determined at the interaction point. A method to account for this energy loss using the calorimeter information is presented. The method provides an estimate of the energy loss on an event-by-event basis thus reducing the statistical fluctuations. The improvement in the momentum resolution by the significant suppression of the non-Gaussian tails of the energy loss is demonstrated using simulated single muon data. The performance of the method on physics samples with muons in the final state is also briefly discussed.