Implementation and performance of a tau lepton selection within the ATLAS trigger system at the LHC

The ATLAS experiment at the Large Hadron Collider (LHC) has an interaction rate of up to $10^9$ Hz. The trigger must efficiently select interesting events while rejecting the large amount of background. The First Level trigger will reduce this rate to around $O(75$ kHz $)$. Subsequently, the High Level Trigger (HLT), comprising the Second Level trigger and the Event Filter, will reduce this rate by a factor of $O(10^3)$. Triggering on taus is important for Higgs and SUSY searches at the LHC. In this paper tau trigger selections are presented based on a lepton trigger if the tau decays leptonically or via a dedicated tau hadron trigger if the tau disintegrates semileptonically. We present signal efficiency with the electron trigger using the data sample $A\rightarrow \tau \tau \rightarrow e \, hadron$, and rate studies obtained from the dijet sample.