Measurement of the performance of the muon reconstruction in ATLAS 
- Marco Vanadia, Oliver Kortner, and Hubert Kroha 
- Max-Planck- Institut fuer Physik, Foehringer Ring 6, 80805 Muenchen

Final states with muons provide clean signatures for many physics
processes at the LHC. The ATLAS detector is optimized for the efficient
reconstruction of muons with high momentum resolution. In pp colli-
sion data recorded at the LHC, the efficiency of the muon
identification
can be determined by means of dimuon decays of J/psi mesons and Z bosons.
The measurements show that the Monte-Carlo prediction of the
muon identification efficiency deviates by less than 1% from the mea-
sured efficiency. The widths of the dimuon invariant mass spectra at
the mass of the J/psi and the Z allow for the measurement of the
muon momentum resolution as a function of the transverse momen-
tum. The measured momentum resolution is in agreement with the
expectation based on the material distribution in the ATLAS detector
and the alignment accuracy of the tracking detectors.