A fast processor for dilepton triggers

We describe a fast trigger processor, developed for and used in Fermilab experiment E-537, for selecting high-mass dimuon events produced by negative pions and antiprotons. The processor finds candidate tracks by matching hit information received from drift chambers and scintillation counters, and determines their momenta. Invariant masses are calculated for all possible pairs of tracks and an even is accepted if any invariant mass is greater than some preselectable minimum mass. The whole process, accomplished within 5-10 μs, achieves up to a ten-fold reduction in trigger rate. (orig.)