Performance and Development of the ATLAS Inner Detector Trigger

The performance of the ATLAS Inner Detector (ID) trigger algo- rithms running online on the high level trigger (HLT) processor farm during LHC Run 1 are presented. The prospects for a full redesign of the ID trigger afforded by the 2013-2014 long shut-down are discussed. The ID trigger HLT algorithms are essential for many signatures within the ATLAS trigger. The performance of the algorithms for electrons, muons and taus is presented. Dur- ing the long shutdown, an additional layer of pixels - the “insertable B-layer” (IBL) will be added to the ATLAS detector. Simulation of the effects this would have on the performance of the current HLT algorithms is presented. The AT- LAS HLT software will also be developed to run as a more flexible single stage rather than the two distinct levels present during the Run 1 operation. Ongoing studies and potential development relating to this will be discussed briefly.