Tau Physics with First Data in ATLAS

Tau leptons, and particularly their hadronic decays, will play an important role at the LHC. The goals for early tau physics in ATLAS include collecting a sample of tau leptons from data with a purity as high as possible so that the identification efficiency of hadronically decaying tau leptons can be measured and the simulation can be tuned. Collecting data with an integrated luminosity of a few hundred pb−1 at an instantaneous luminosity of 1031 cm−2s−1 will provide a unique opportunity in ATLAS to access and understand statistically significant tau samples from Standard Model processes at relatively low transverse momenta. Identification of tau leptons in ATLAS is particularly challenging due to overwhelming background coming from QCD dijet production. Processes like the production of W and Z bosons and top quark pairs will lead to samples of a few hundred to a few thousand identified hadronic tau decays. Hadronically decaying tau leptons will then become a well understood probe for discovery physics like searches for Higgs bosons, SUSY, or exotic phenomena. Feasibility studies for analyses which can be envisaged with an integrated luminosity of 100 pb−1 to 1 fb−1 are presented.