Triggering on hadronic tau decays in ATLAS: Semiconductor tracking detectors in action

Identifying the decay of the hadronic tau leptons plays a crucial role in the search for physics beyond the Standard Model as well as in Standard Model measurements. However, these decays are difficult to identify and trigger on due to their resemblance to QCD jets. Given the large production cross-section of QCD processes, designing and operating a trigger system with the capability to efficiently select hadronic tau decays, while maintaining the rate within the bandwidth limits, is a difficult challenge.This contribution will summarize the status and performance of the ATLAS tau trigger system during the 2011 data taking period, emphasizing the key role of semiconductor tracking detectors for tracking and vertexing. Different methods that have been explored to obtain the trigger efficiency curves from data will be shown. Finally, in light of the vast statistics collected in 2011, future prospects for triggering on hadronic tau decays in this exciting new period of increased instantaneous luminosity will be presented.

► The ATLAS Tau trigger successfully operated during the 2011 run.
► Tracking is a core part of the triggering process of ATLAS.
► The system attained very high levels of efficiency for track reconstruction.
► Data/simulation comparisons of tau trigger show very good agreement.