Performance of the ATLAS Jet Trigger

There have been a lot of recent changes in the ATLAS jet trigger. The standard strategy, based on Regions Of Interest, is not well-suited for multi-jet events since it leads to pathologies and efficiency losses. This philosophy has been changed for the jet trigger, and we now have the possibility of unpacking the full calorimeter at Event Filter and (even for a small subset of the events) at an intermediate level between Level-1 and Level-2. We also moved to the use of calibrated scale at trigger level, and to the application of noise cuts to reduce rate spikes. We will present the performance of the jet trigger in 2011, when most of these changes were operational