An analysis of 900 Amp Charm data prescale events to determine
     calorimeter efficiency in the trigger.
            MJL - 11/13/92

I have analyzed the bulk of the 900 Amp D data TFI-prescale
events. I required two good opposite-sign target hadrons that
did not fire 2 or more muon counters in station four. I required
silicon tracks to restrict the study to the silicon aperture.
I then made a cut on the D mass (1.82 to 1.9 GeV). 
        Cuts         Events        Efficiency
       --------      ------        -----------
       none           408             100%
       nx1nx3bar      377              92%
       susd           344              84%
       matrix         387              95%
       3 cuts above   297              73%
       hh-trigger     172              42%
this implies then that the calorimeter trigger
efficiency for D's (if we assume hadron pairs of
the D mass are similar to real D's) is 57%.
With this efficiency I now seem to get a reasonable
D cross section.

I have tried a rough simulation of this with the monte carlo.
I took the hadron pair energy, smeared it with a resolution
of 15% (is this a reasonable resolution?) and made a threshold
cut at 40 GeV. This gives an efficiency for the calorimeter
of 95%. If I raise the threshold to 55 GeV then I get 62% which
is getting near the measured value above. This is a threshold on
the total energy. What layers of the calorimeter were actually
used in the E-low?
					Mike