Muon Track Reconstruction in the ATLAS Experiment

he Muon Spectrometer for the Atlas experiment at the LHC is designed to identify muons with transverse momentum greater than 3 GeV/c and measure muon momenta with high precision up to the highest momenta expected at the LHC. The 50-micron sagitta resolution translates into a transverse momentum resolution of 10% for muon transverse momenta of 1 TeV/c. Precise tracking is provided by Monitored Drift Tubes at central and forward rapidities and by Cathode Strip Chambers at very forward rapidities. Dedicated alignment systems are a critical component of the design to attain such precision. Final muon tracks are obtained by combining tracks from the Muon Spectrometer and the Inner Detector. We review the recent changes to the design of the muon reconstruction software and discuss new pattern recognition approaches developed to fully exploit the capabilities of the ATLAS detector. Track fitting and the handling of the inert material are also presented. The pattern recognition algorithms are required to be fast and efficient for use in the high-level trigger, and they have been designed to take advantage of the characteristics of the signals from the different detector technologies. Finally, we present the latest muon reconstruction performance results based on detailed studies with realistic Monte Carlo simulation, including the impact of anticipated background in the ATLAS detector and of misalignments.