[d2n-analysis-talk] BB Cer pion rejection

[posik at jlab.org]

Hi all,

 I have just looked at some BigBite Ceerenkov pion rejection factors for
each mirror on the RHRS side of the Cerenkov. I selected pions by using
the T6 trigger. These pions were selected by using a cut on the total
shower energy and the preshower energy (see pion_pid_0.gif for the cut).
I also used a E/p cut of E/p<0.8, (see the Ep.gif plot). I should note
that the trigger here is different than that of the 4-pass run that I
showed the shower calibration on, this was before the BB shower summing
module was included again in the trigger, so we trigger on many more
pions than with the 4-pass runs I showed the shower calibration on.

Below is a table of the pmt, pion events selected for that mirror. I then
applied a cerenkov TDC and ADC cut and listed the events that remained. I
did this for 0,1,2 and 3 photoelectrons. I found that the Cerenkov pion
rejection factor is an average 10^2. PMTs 19 and 20 could not be looked at
because no events were left when I applied the mirror cut, these would be
the two bottom mirrors. I am going to replay a few more runs to get a few
more statistics, but thought that I would give an update.


pmt	  pion events 	cer events (0pe)	cer events(1pe)		cer events(2pe)		cer
events(3pe)
==============================================================
11	    768                11                                1             
                      0                                         0
12       782                27	                                0          
                         0                                         0
13      1220               21                                6            
                       3                                         3
14      2055              25                                 4            
                       2                                         2
15      2143              25                                 6            
                       5                                         5
16      2273              6                                   2           
                        1                                         1
17      1961              31                                18            
                     13                                       11
18      131                3                                  0           
                         0                                         0
19       -                  -                       -                    
-                      -                            -
20       -                  -                       -                     
-                      -                           -


-Matt
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