Z -> tau tau cross section measurement in proton-proton collisions at 7 TeV with the ATLAS experiment

The Z->tautau cross section is measured with the ATLAS experiment at the LHC in three different final states determined by the decay modes of the $\tau$ leptons. The analysis is based on a data sample collected during 2011, corresponding to an integrated luminosity of 1.34-1.55 fb-1, depending on the final state, at sqrt{s} = 7 TeV proton-proton center-of-mass energy. Cross sections are measured individually for each final state in a fiducial kinematic phase space, and also extrapolated to the full phase space in the invariant mass region 66 - 116 GeV. The separate cross sections are combined and the product of the total Z production cross section and Z->tautau branching fraction is measured to be 0.92 +/- 0.02(stat) +/- 0.08(syst) +/- 0.03(lumi) nb, in agreement with the NNLO theoretical expectation. The data is also used to study variables related to hadronic tau lepton identification. A good description of these variables by the Monte Carlo simulation is seen.