The performance of the jet trigger for the ATLAS detector during 2011 data taking

Abstract

The performance of the jet trigger for theATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton–proton collisions with a centre-of-mass energy of 7TeV and heavy ion collisions with a 2.76TeV per nucleon–nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40MHz nominal maximum bunch crossing rate to the approximate 400Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60GeV. Jets reconstructed in the final trigger level and corresponding to offline jets with transverse energy greater than 60GeV, are reconstructed with a resolution in transverse energy with respect to offline jets, of better than 4% in the central region and better than 2.5% in the forward direction.