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User name posik
Log entry time 13:32:42 on March 04, 2009
Entry number 264558
keyword=BB cer 1917-1919 analysisI have looked at the BB cerenkov for run 1917,1918 and 1919. Fig 1 shows the tdc cuts that were used to define the mirror cuts, Fig 2 shows the mirror locations for each pmt. Fig 3 shows the adc with mirror cuts, the red curve is the adc with a mirror cut corresponding to that pmt, and the blue curve is the adc with a mirror cut on a mirror far from the pmt. Fig 4 shows the adc vs tdc plots and Fig 5 is again the adc vs tdc but zoomed in.
I tried to find the number of photoelectrons for each adc. To do this I subtracted the peds(blue curve) from the adc(red curve) and fit a gaussian. I got the number of photoelectrons by using the formula #photoelectrons = (mean/sigma)^2. This is shown in fig 6(for large angle). I quickly found out using this method on the small angle pmts(1-10) doesn't give a reliable # of pe, I found it to be ~3, which assuming the 1 photoelectron peak is at channel 30 I would expect something around 7(average adc red curve ~channel 200). I think this is because looking at fig 3 for the small angle side there is a lot of overlap between the red and blue curves which would result in a "contaminated" adc signal.
Now if I look at the large angle side (pmt 11-20) subtracting peds and
make a gaussian fit fig 6. I find pmt 12 sees ~7 photoelectrons and pmts
13-18 see ~ 5 photoelectrons and pmts 11,19,20 see ~3 photoelectrons.
This is in better agreement with the one photoelectron peak being at
channel 30. I think the reason 11,19 and 20 give a smaller number is
because they are at the top and bottom positions in the cerenkov
detector(near the edge of the acceptance) and have less statistics.
A copy of this log entry has been emailed to: brads,meziani,flay,xqian
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
