Tau lepton reconstruction and identification with the ATLAS detector at the LHC

The overall performance of the idenfication and measurements of hadronically decaying $ au$ leptons in a wide dynamic range of transverse energies, spanning from (10-15)~GeV up to at least 500 GeV, with the ATLAS detector at the LHC is presented. Hadronically decaying $ au$ leptons are reconstructed by matching narrow calorimetric clusters with a small number of racks. Two complementary approaches, the calorimeter-seeded and the track-seeded algorithm, have been developed to efficiently reconstruct these decays while providing the required large rejection rates against otherwise overwhelming backgrounds from jet production via QCD processes. Specific performance aspects of particular interest for the reconstruction of hadronic $ au$ candidates are discussed together with the overall performance in terms of efficiency versus rejection rate of the large background from QCD jets expected at the LHC. Prospects for measurements with first data such as the determination of fake rates are discussed.