The Tau Trigger at the Atlas Experiment

The tau trigger system is a component of the Atlas trigger system. Its purpose is to select events of interest containing hadronically decaying taus, which are signatures for new physics such as Higgs decays, while rejecting background events. It is composed of three levels, the lowest being hardware based and the higher levels software based. The tau trigger uses cuts on calorimeter and tracking information to select good tau candidates, the stringency of which cuts vary with luminosity. Tau trigger efficiency will be measured from the QCD tau fake rate, with a tag and probe analysis using Z boson decays, and from semi-leptonically decaying t t bar events triggered by a 4-jet trigger.