Performance of the Reconstruction and Identification of Hadronic Tau Decays with ATLAS

The reconstruction algorithm, energy calibration, and identification methods for hadronically decaying tau leptons in ATLAS are described in this note. Three identification methods are optimised to discriminate tau-leptons from QCD jets, including a cut-based identification, a projective likelihood, and boosted decision trees. Two vetoes are optimised to reject tau candidates from electrons, including a cut-based veto and boosted decision tree veto. Systematic uncertainties on the tau energy scale are determined using Monte Carlo samples. The tau identification efficiency is determined from a selection of Z->tautau and W->taunu events in 2011 ATLAS data. The probability for electrons to be misidentified as hadronic tau decays is measured from a selection of Z->ee events in 2011 ATLAS data.