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The current discriminator nominal setting was 0.39 mip. Ideally, this
value would be lower since it gives less than 100% efficiency for the
MVD strips. I did not calculate the exact efficiency, but based on
the ADC distributions shown in this study, the efficiency is probably
around 95-98%.
The performance of the discriminators measured for protyotypes produced
in the hp process seems good enough for use in a multiplicity trigger
based on the MVD barrel or pads. The correlation between the true
multiplicity (meaning the expected number of channels "on" for a
discriminator with no channel to channel variation) and the measured
multiplicity (meaning the expected number of channels "on" for
discriminators with the measured channel to channel variation)
is linear and narrow. This was checked over a range of multiplicites
from 0.2% of the expected multiplicity for central Au+Au collisions
up to the full central Au+Au multiplicity. The slope of the correlation
is very close to the ideal value of 1 and varies about a percent
with pseudorapidity from -4 to 4.
John Sullivan
sullivan@lanl.gov
updated Thursday December 18, 1997