Implementation and Performance of the ATLAS Jet Trigger

ATLAS is one of the main experiments at the LHC. Its trigger system has been designed to be flexible in order to cover a wide range of physics topics, while reducing the rate from the nominal 40 MHz to about 200 Hz. In order to achieve this, the ATLAS trigger system searches for high pT objects, like leptons, jets, photons, or missing transverse energy. The jet trigger starts at the first level trigger with dedicated processors that search for high ET hadronic energy depositions. At the second level trigger, the jet signatures are verified with the execution of a dedicated, fast cone reconstruction algorithm followed by a simple calibration scheme. In the third level trigger any of the offline jet reconstruction algorithms can be used. In this paper we will present the challenges of the jet trigger, describing the implementation and the expected performance.