Calibration of the ATLAS Precision Muon Chambers and Study of the Decay τ→μμμ at the Large Hadron Collider

The Large Hadron Collider (LHC) is designed to collide protons at centre-of-mass energies of up to 14 TeV. ATLAS, one of the main experiments at the LHC, is equipped with a muon spectrometer comprising three superconducting air-core toroid magnets and 1150 precision drift tube (MDT) chambers. An improved method for the precise calibration of the space-to-drift-time relationships of the MDT chambers operated in the toroidal magnetic field, using curved muon tracks, has been developed and verified. The sensitivity of ATLAS on the lepton flavour violating tau decay into three muons has been evaluated using simulated data. Taking theoretical and experimental systematic uncertainties into account, it is estimated that an upper limit on the signal branching ratio of 5.9·10-7 at 90% confidence level can be achieved with an integrated luminosity of 10 fb-1.