[d2n-analysis-talk] Shower and Preshower Energies in BigBite

[Diana Parno]

Hello all,

I've been looking at PID through the BigBite shower and preshower  
energies for 3He elastics and 3He production runs at five-pass, and  
I'm pretty confused by what I'm seeing. I've attached some plots of  
the total energy (0.5*BB.ts.ps.e + BB.ts.sh.e) versus the preshower  
energy (BB.ts.ps.e) for various trigger conditions (from the  
evtypebits) and for particle charges of +1 and -1 (as determined by  
the optics code). The units are approximately MeV.

The first attachment shows the energies for several 3He elastics runs,  
taken at 1 pass, chained together (Runs 1203-1215, to be precise, from  
February 9-10). You can see a few apparent populations: one hugging  
the y-axis (pions?); one, at a preshower energy of about 200, that's  
emphasized in the positive-charge data (protons?); and one with a wide  
range of preshower and total energies (electrons?) What I don't  
understand is the way the putative electron distribution seems to move  
to higher preshower and total energies for T2 and T6. I had also  
thought that T6 was typically a higher threshold than T1; though I  
haven't found the thresholds for this run period yet, shouldn't the T6  
data display some cutoff at low shower energies, rather than closely  
reproducing the T2 data?

The second attachment shows T1 data for two runs at five-pass (3He  
target), Run 1314 (February 12) and Run 1972 (March 4). The prescale  
for T1 was high (1700 and 1400, respectively), which is why there is  
relatively little data. Here, we see only two distinct populations;  
there is no population along BB.ts.ps.e=0, but the events at  
BB.ts.ps.e~200 cannot be protons because they are not emphasized for  
positive-charge events.

The third attachment shows T2 data for Run 1314 (left) and Run 1972  
(right), plus Run 1449 (middle), a February 15 run taken right after  
the fix to the NIM bin power supply. (There are no T1 data available  
for Run 1449 due to prescales). Does Run 1449 show a merger of the two  
populations we saw in the T1 data? Why might Run 1972 show such a  
different shape from the others?

The fourth attachment shows T6 data for the three production runs. My  
understanding was that the T2 trigger included a Cerenkov signal and  
the T6 trigger did not; I don't understand why the T6 data would look  
so similar to the T2 data, if that's the case.

I'd appreciate any thoughts you might have. I've retrieved the  
threshold data from the HALOG start-of-run entries and copied it  
below. Matt's "Notable Events List" on the wiki assigns BB_Sh to T6  
and BB_Sh_2 to T1.

Thanks,
Diana

Runs 1203-1215:
- Threshold for 'BB_Sh' is -0.133 V (1806)
- Threshold for 'BB_PSh' is -0.050 V (1976)
- Threshold for 'BB_Sh_2' is -0.080 V (1925)
- Threshold for 'BB_Cer' is -0.070 V (1925)

Run 1314:
- Threshold for 'BB_Sh' is -0.133 V (1806)
- Threshold for 'BB_PSh' is -0.020 V (2038)
- Threshold for 'BB_Sh_2' is -0.080 V (1925)
- Threshold for 'BB_Cer' is -0.070 V (1925)
Run 1449:
- Threshold for 'BB_Sh' is -0.135 V (1802)
- Threshold for 'BB_PSh' is -0.020 V (2038)
- Threshold for 'BB_Sh_2' is -0.120 V (1843)
- Threshold for 'BB_Cer' is -0.070 V (1925)
Run 1972:
- Threshold for 'BB_Sh' is -0.110 V (1854)
- Threshold for 'BB_PSh' is -0.015 V (2048)
- Threshold for 'BB_Sh_2' is -0.110 V (1864)
- Threshold for 'BB_Cer' is -0.070 V (1925)

3He elastics (1-pass):
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Trigger 1 in production running:
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Trigger 2 in production running:
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Trigger 6 in production running:
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