The ATLAS High Level Trigger

ATLAS is one of two general-purpose detectors currently being built at the Large Hadron Collider, the next generation of proton-proton collider due to start in 2007. Due to the high rate of events as well as the large number of read-out channels, the trigger system for such a detector is quite challenging. ATLAS uses a three level trigger system where the first level is hardware based and the high level triggers are software based. This talk will present the physics motivation of the ATLAS detector and the chosen selection strategies for the trigger, the implementation of the High Level Trigger software and some related measurements.