Architecture and Performance of the Inner Detector Trigger of the ATLAS detector

The rising instantaneous luminosity of the LHC poses an increasing challenge to the pattern recognition algorithms for track reconstruction at the ATLAS Inner Detector Trigger. ATLAS has so far used both histogramming-based and combinatorial algorithms for the task of Level 2 (L2) track reconstruction. IDScan and SiTrack algorithms are the two main pattern recognition algorithms . In light of the experience from the data taking in 2011, a new software framework, called L2star, is being developed that will provide a suite of configurable tools, based on modularising the existing code and increasing the re-use of components, to provide the optimal solution in the various trigger signatures at higher luminosities. This new framework is presented. IDScan and SiTrack algorithms show very good performance in 2011 Data for electron and muon trigger signatures.