Performance and Development of the ATLAS Inner Detector Trigger

The performance of the ATLAS Inner Detector (ID) trigger algorithms running online on the high level trigger (HLT) processor farm during LHC run I are presented. The prospects for a full redesign of the ID trigger afforded by the 2013-2014 long shutdown are discussed. The ID trigger HLT algorithms are essential for many trigger signatures within the ATLAS trigger. The performance of the algorithms for muons, electrons, taus and b-jets is presented. During the long shutdown, the ATLAS HLT software will be developed to run as a more flexible single stage rather than the two distinct levels present during the run I operation. This poses signifi- cant challenges for the trigger algorithms in terms of execution time and physics performance. Possible increased use of parallelism in the algorithm processing is being explored. The possible improvements in the timing and efficiencies of the new Inner Detector triggers within the new merged single stage architecture, including increased parallelism are described.