A multiplicity jump trigger for fixed target charm and beauty experiments

Using the E791 spectrometer we have tested a multiplicity jump trigger that makes use of thin quartz plates to count the number of particles before and after a decay region just downstream of a thin tungsten target struck by a 500 GeV pion beam. The detector is sensitive to about 2.7 tracks being created between the plates at the 1 sigma level. This performance level may enhance charm events by a small amount, and should lead to an enrichment of well over 100 for BB events.