Tau Reconstruction, Energy Calibration and Identification at ATLAS

Tau leptons play a central role in the LHC physics programme, in particular as an important signature in many Higgs boson and Supersymmetry searches. They are further used in Standard Model electroweak measurements, as well as detector related studies like the determination of the missing transverse energy scale. Copious backgrounds from QCD processes call for both efficient identification of hadronically decaying tau leptons, as well as large fake rejection. A solid understanding of the combined performance of the calorimeter and tracking detectors is also required. We present the current status of the tau reconstruction, energy calibration and identification with the ATLAS detector at the LHC. Identification efficiencies are measured in Wtaunu events in data and compared with predictions from Monte Carlo simulations, whereas the misidentification probabilities of QCD jets and electrons are determined from various jet-enriched data samples and from Zee events, respectively. The tau energy scale calibration is described and systematic uncertainties on both energy scale and identification efficiencies discussed.