The ATLAS Level-1 Central Trigger

The ATLAS Level-1 trigger system is responsible for reducing the anticipated LHC collision rate from 40 MHz to less than 100 kHz. This Level-1 selection identifies jets, electrons/photons and muons, with additional triggers for missing and total energy. These inputs are used by the Level-1 Central Trigger to form a Level-1 Accept decision. This decision, along with clock and summary information, is then passed into the higher levels of the trigger system and sub-detectors. Results from commissioning the Central Trigger with cosmic rays and its performance during the first collisions will be shown.