In-situ Determination of the ATLAS Muon Performance

The ATLAS detector allows for the precise and efficient reconstruction of muons. Muon tracks are reconstructed with 97% efficiency and a momentum resolution about 2% for most of the range and better than 10% for transverse momenta up to 1 TeV/c up to |eta|<2.7. We present methods which allow us to measure the performance of the muon identification during the operation of the ATLAS detector. The muon reconstruction efficiency and the momentum resolution can be determined with muons from Z and J/psi decays. The Z and the J/psi resonance can also be used to refine the magnetic field map.