The Performance and Development of the ATLAS Inner Detector Trigger

A description of the ATLAS Inner Detector (ID) software trigger algorithms and the performance of the ID trigger for LHC Run 1 are presented, as well as prospects for a redesign of the tracking algorithms in Run 2. The ID trigger HLT algorithms are essential for a large number of signatures within the ATLAS trigger. During the shutdown, modifications are being made to the LHC machine, to increase both the beam energy and luminosity. This in turn poses significant challenges for the trigger algorithms both in terms of execution time and physics performance. To meet these challenges the ATLAS HLT software is being restructured to run as a single stage rather than in the two distinct levels present during the Run 1 operation. This is allowing the tracking algorithms to be redesigned to make more optimal use of the CPU resources available and integrate new detector systems being added to ATLAS for post-shutdown running. Expected future improvements in the timing and efficiencies of the Inner Detector triggers within the are also discussed. In addition, potential improvements in the algorithm performance resulting from the additional spacepoint information from the new Insertable B-Layer are presented.