HIGHER-LEVEL TRIGGER SYSTEMS FOR THE HERA-B EXPERIMENT

The HERA-B experiment[1, 2] is designed for observation of CP violatio n in the B-meson system at the HERA machine in DESY. The data acquisit ion and triggering system must cope with a half million detector chann els, a 40 MHz interaction rate and a signal to background ratio of 10( -10). A highly selective multi-level trigger and high bandwidth data a cquisition 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 un der Linux. The switch to the 4th level trigger farm will be based on F ast-Ethernet.