Higher level trigger systems for the HERA-B experiment

The HERA-B experiment is designed for observation of CP violation in the B-meson system at the HERA machine in DESY. The data acquisition and triggering system must cope with a half million detector channels, a 40 MHz interaction rate and a signal to background ratio of 10/sup -10/. A highly selective multi-level trigger and high bandwidth data acquisition system has been designed and is currently being implemented. The second-level event buffer and mid-level trigger switch will be built from DSP boards carrying SHARC processors. The second and third level trigger code will run on a farm of 100-200 Pentium processors under Linux. The switch to the 4th level trigger farm will be based on Fast-Ethernet.