The Level 0 trigger for the DØ detector

The DØ detector has completed its first data taking run at the Fermi National Accelerator Laboratory´s p¯-p Tevatron collider. The Level 0 trigger system is the DØ experiment´s first trigger level used to identify colliding beam crossings containing interactions. It consists of two hodoscopes of scintillation tiles located just outside the DØ 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 position of the interaction and an indication of the occurrence of multiple interactions are available for subsequent trigger decisions. In addition, the Level 0 trigger is used as a luminosity monitor for DØ. Results on the performance of the Level 0 trigger are presented