Dr. sue cheatham (Technion)
During the 2011 data-taking run, the Large Hadron Collider (LHC) collided proton beams at the energy of 7 TeV in the centre-of mass, as well as heavy ions at the centre of mass energy of 2.76 TeV. The ATLAS Trigger is designed to reduce the rate of events from the nominal maximum bunch-crossing rate of 20 MHz to approximately 400 Hz, which will then be written on disk offline. The online selection of events containing jets is done using a dedicated jet trigger. The rate from jet events is very high, with a steeply falling spectrum in the distribution of the transverse energy. The jet trigger has been designed to keep an approximately constant jet rate of 0.5 Hz in various transverse momentum intervals and accounts for around 10% of the total trigger rate. During the 2011 data taking the jet trigger at Level 1 was fully efficient for jets with transverse energies above 25 GeV, while full efficiency was reached for energies above 60 GeV for jets identified up to the third trigger level (the Event Filter). The transverse energy resolution of jets reconstructed in the latter region of the spectrum is better than 4%. In this poster, the overall performances of the jet trigger during the 2011 data taking will be summarised, together with important updates used during the 2012 run. In addition, the expected performance of the jet trigger in the LHC Run-II, to start in 2015, will be described.