Here is a picture of the corrected E-counter TDC values from the tagger.
Each of the 384 E-counters is independantly shifted in time so that the
first pulse is centered on TDC value 1350. A good tagger hit requires
the TDC value to be within +/- 3 TDC counts of 1350. (I believe it is
1/2 ns per TDC count). The nasty bit around e-counter 50 to 75 was possibly
due to a noise or threshold problem in the tagger. It corresponds to energies
from about 4.4 to 4.9 GeV.
Here is the tagger energy versus the calibrated calorimeter energy.
This includes some gain-matching in addtion to the gain-matching
done online.
Here's a snapshot of the gain factor finding program "in action". It is
an iterative process using data collected while the beam was centered on
each block in the array. Each gain factor is calculated assuming the other
24 gain factors are correct. Convergence occurrs when the top table is
all 1's. The bottom table then represents the final gain factors.
Here is a preliminary plot of the Pb-glass I resolution. What is plotted
is sigma/E times sqrt(E). The fact that it is so linear indicates the
constant term is small. The resolution of 7.88%/sqrt(E) includes the 100 MeV
bin width of tagger energies used for each point. This will need to be taken
out to get the true energy resolution of the Pb-glass. The error bars are
based only on the area of the gaussian's fit to get the sigma's and means
(i.e. I'm disclaiming the error bars for now).
David Lawrence
davidl@jlab.org
Wed Jul 26 12:56:24 EDT 2000