Performance of Tau Reconstruction and Identification in 2011

Poster for LHCC 2012. The reconstruction algorithm, energy calibration, and identification methods for hadronically decaying tau leptons in ATLAS are described. Three alternative identification methods are optimised to discriminate tau leptons from QCD jets: a cut-based discriminant, discrimination with a projective likelihood, and discrimination with boosted decision trees. Two identification methods are optimised to reject electrons mis-identified as tau leptons: a cut-based discriminant and discrimination using boosted decision trees. For a signal identification efficiency of ≈50%, rejection factors in the range 50–200 for jets and 50–1000 for electrons are achieved. Systematic uncertainties on the tau energy scale are determined using Monte Carlo samples. The tau identification efficiency is determined from a selection of Z → ττ and W → τν events in ATLAS data taken during summer 2011, corresponding to an integrated luminosities of 0.8 fb^{-1} and 1.4 fb^{−1}, respectively.