The ATLAS experiment under construction at CERN is due to begin operation at the end of
2007. The detector will record the results of proton-proton collisions at a center-of-mass
energy of 14 TeV. The trigger is a three-tier system designed to identify in real-time
potentially interesting events that are then saved for detailed offline analysis. The trigger
system will select approximately 200 Hz of potentially interesting events out of the 40 MHz
bunch-crossing rate (with 10 9 interactions per second at the nominal luminosity).

The ATLAS experiment under construction at CERN is due to begin operation at the end of
2007. The detector will record the results of proton-proton collisions at a centerof-mass
energy of 14 TeV. The trigger is a three-tier system designed to identify in real-time
potentially interesting events that are then saved for detailed offline analysis. The trigger
system will select approximately 200 Hz of potentially interesting events out of the 40 MHz
bunch-crossing rate (with 10 9 interactions per second at the nominal luminosity). Algorithms …