Effect of calorimeter resolution and pile-up on trigger rates

In the high rate Isabelle environment it has long been recognized that fast time resolution and short memory times are highly desirable. Unfortunately, calorimeters have been inherently slow devices on the time scales of interest. The bunched beam scheme of Isabelle, Phase I, offers some temporary respite. The instantaneous luminosity is quite high and leads to an interaction probability of .2 per crossing. However, there is no hope of tagging multiple interactions within a bunch using time resolution alone. In that sense a time resolution of 200 ns is as good as 5 ns, and conventional calorimeter technologies (including gas multiplication readout) can be used