Tools for Trigger Aware Analyses in ATLAS

In order to search for rare processes, all four LHC experiments have to use advanced triggering methods for selecting and recording the events of interest. At the expected nominal LHC operating conditions only about 0.0005% of the collision events can be kept for physics analysis in ATLAS. Therefore the understanding and evaluation of the trigger performance is one of the most crucial parts of any physics analysis. ATLAS’s first level trigger is composed of custom-built hardware, while the second and third levels are implemented using regular PCs running reconstruction and selection algorithms. Because of this split, accessing the results of the trigger execution for the two stages is different. The complexity of the software trigger presents further difficulties in accessing the trigger data. To make the job of the physicists easier when evaluating the trigger performance, multiple general-use tools are provided by the ATLAS Trigger Analysis Tools group. The TrigDecisionTool, a general tool, is provided to retrieve the results of the trigger execution, which are the passed/failed decision for each trigger line and the objects reconstructed by the trigger together with their ancestral relations. The configuration of the trigger is also accessible through this tool, in particular the various scaling factors. A second tool, the TrigMatchTool, is available to associate particle-like objects reconstructed by the trigger to object s derived in the full reconstruction of either real or simulated data. Finally, a common in-situ performance framework is provided for calculation and storage of trigger efficiencies, and serving them to the physics analyst. In this presentation we will describe these tools.