Tau reconstruction and identification with 7 TeV collisions in ATLAS

The first LHC collisions at a centre-of-mass energy of recorded with the ATLAS detector are used to study the reconstruction and identification algorithms for hadronic τ decays. Although the dataset used here, corresponding to an integrated luminosity of , contains a small number of real τ leptons, the background jets reconstructed as τ candidates can be used to assess performance aspects of these algorithms. Distributions of identification variables are compared in data and Monte Carlo samples, and the background efficiency of τ identification criteria is measured in a QCD dijet enriched data sample. Good agreement is observed between data and the fake τ candidates selected from simulated QCD dijet events, giving confidence in the performance of the algorithms on real τ leptons, to be observed soon.