Measurement of Muon Energy Loss in ATLAS

The ATLAS muon spectrometer is designed to provide precise momentum measurement for muons up to O(1 TeV/c). The fluctuations in the energy loss of muons in the material downstream of the muon spectrometer could deteriorate the physics performance, which requires the momentum to be expressed at the interaction point. A method to account for this energy loss using the calorimeter measurement is presented. The method provides an estimation of the energy loss on an event-by-event basis thus reducing the statistical fluctuations. The momentum resolution is optimized with significant suppression of the non-Gaussian tails as it is demonstrated using simulated single muon data. The performance of the method on physics samples with several muons in the final state, is also briefly described.