The ATLAS Jet Trigger at 13 TeV

Abstract

The new Large Hadron Collider centre of mass energy and expected high luminosity conditions impose more demanding constraints on the ATLAS online trigger than ever before. The immense rate of proton-proton collisions must be reduced from the bunch-crossing rate of 40 MHz to approximately 1 kHz before the data can be written to disk for offline analysis. The ATLAS Trigger System performs real-time reconstruction and selection of these events in order to achieve this reduction. The selection of events containing jets is extremely challenging at a hadron collider where nearly every event contains significant hadronic activity. It is, however, of crucial importance for several physics analyses, including early searches for new physics in the new kinematic regime. Following the very successful first Large Hadron Collider run in 2010-12, the ATLAS Trigger has been upgraded, to include a new hardware topological module and a restructured High Level Trigger system, merging the two previous software-based processing levels. After summarising the overall performance of the jet trigger during the first Large Hadron Collider run, the software design choices and use of the topological module will be reviewed. The expected performance of jet trigger for the second LHC run is described and compared with the first trigger results from the Run 2 collisions data.