[Halld-tagger] DBeamPhoton tests

[Alexander Austregesilo]

Hi,

I looked at the accidental corrected rho yields as a function of energy 
for the three test runs. You can see the plots on this wiki page:

https://halldweb.jlab.org/wiki-private/index.php/2020_TagM_Threshold_Test

Comparing the two versions with and without the requirement of ADC/TDC 
matching for the hodoscope, I only see a loss of events below 1% in 
almost the full energy range. There is only one 100MeV-wide bin near 
9.1GeV, where the loss is about 15%. Could this be a sign of a broken or 
miscalibrated TDC?

For the 2 runs before the adjustment of the microscope thresholds, the 
loss of rho events with tagged beam photons is close to 30% as expected. 
Once the thresholds were fixed in run 71724, the loss goes down to 10% 
in the higher-energy part of the microscope, while it completely 
recovers for the low-energy part. What is the reason for this 
discrepancy? New vs old fibers?

Best regards,

Alex