[d2n-analysis-talk] BB cer peds

[posik at jlab.org]

Hi Brad,

  I am working on calibrating the big bite cerenkov detector (aligning the
one photoelectron peaks) and think that I have it all done for our
running in March and the end of February. I am doing replays now to
check the calibration with the production runs. I already checked the
calibration on the one LED data and that looks good.

 I am now looking at the beginning of the d2n experiment and trying to
find the pedestal locations of ADC signals. I should note that over this
run period we were using the 792 ADC. I found one ped run from early Feb.
run 1087. I attached the plots of that run below.

 Since there was a lot of changing during this period, I wanted to look at
the peds for other runs. I decided to look at run 1258 which is a onepass
H2 run and to check the ped I plotted ADC from PMT 1 and I used a T8 cut
"(DBB.evtypebits&1<<8)==(1<<8)" on an ADC spectrum. What remains after
that pulser cut is three peaks in the ADC (blue curve in
elastic_ped.png). To get a better under standing of where the ped is, I
decided to plot the same ADC and apply a T2 and TDC cut and see if I can
see a threshold(this is the red curve in the elastic_ped.png). I then
scaled the T8 cut histo to T2+TDC cut histo for comparison. Looking at
these two histos, there is a suppression in left most peak, does that
mean that is the ped? But then what about the center and right most
peaks?

Thanks
Matt
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