THE LEVEL 0 TRIGGER FOR THE D0 DETECTOR

The Dempty set detector [1] has completed its first data taking run at the Fermi National Accelerator Laboratory's pBAR-p Tevatron collider. The Level 0 trigger system is the Dempty set experiment's first trigg er level used to identify colliding beam crossings containing interact ions. It consists of two hodoscopes of scintillation tiles located jus t outside the Dempty set central tracking region. The Level 0 trigger provides a fast measurement of the interaction position along the beam axis for use in early trigger decisions. A slower, more accurate posi tion of the interaction and an indication of the occurrence of multipl e interactions are available for subsequent trigger decisions. In addi tion, the Level 0 trigger is used as a luminosity monitor for Dempty s et. Results on the performance of the Level 0 trigger are presented.