More calculations on PID and on the Cherenkov design

[gen (Eugene Chudakov) <gen@jlab.org>]

Hall D PID Mail List:


I improved my calculations for the PID efficiency and updated the page 
http://www.jlab.org/~gen/gluex/gas_cher_geom.html

In summary:
a) About 30-50% of kaons would reach the Cherenkov detector.
b) For processes with low multiplicities (fast kaons) the impact from
   the Cherenkov detector on the rejection of events with pions only 
   would be significant (4 times more useful events selected at a given
   rejection power).
c) For events with high multiplicities Cherenkov detectors could
   be still helpful (about 50% gain in efficiency).
 
d) An aerogel detector would help to provide a strong rejection power.

e) MC-calculated photoelectron yields are about 2 times higher
   than the measured yields of several existing detectors. I used this
   as a "calibration" for the number of radiated photons in MC, 
   reducing them by a factor of 2.

f) Using a 4-5" quartz PMT with a C4F10 radiator would provide 
   a 90% detection efficiency for pions at 2.9 GeV/c.
   
g) The electromagnetic background (pair production) by beam photons
   would give a rate of 50kHz in the gas Cherenkov detector, which
   seems to be low enough.

Eugene