Performance and improvements of the ATLAS jet trigger system

The ATLAS jet trigger is the primary means for selecting energetic jets produced in LHC collisions. The ATLAS trigger system has a three level structure, and was designed based on the concept of Regions Of Interest (RoI), wherein only areas of the detector around interesting objects identified at the first level are accessed at the higher levels. The first implementation of the ATLAS jet trigger was entirely RoI based. This was changed in 2011 with the addition of the possibility to access information from the full calorimeter at the Event Filter and similarly in 2012 for the second level. This change enhances the flexibility and versatility of the system as well as improving efficiencies in multi-jet events. This paper presents the performance of the jet trigger in 2011 and an overview of the new features available for 2012.