Pion Meeting May 20 2022 3:30PM ET

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Zoom link: https://jlab-org.zoomgov.com/j/1608212513?pwd=M25LR1hzN3hLWm0xaFFETjZ0U1lQZz09

Agenda

Agenda:

1. Update on prototyping the pion detector- calculating the number of photoelectrons for different experiments, and comparing with the number of photoelectrons in the simulations - (Elham) [1]
2. Fitting to Poisson distribution (Elham) [2]
3. Comparison of PEs/muon from simulation to prototype (Elham) [3]
4. Add downstream shielding to the new design of lead donut and pion detector system - (Elham) [4]
5. AOB

Attendance

David, Elham, Wouter, Sudip, Carl, Kate, Neven

Minutes

1. Fitted prototype data to Poisson distributions to estimate number of PEs, get around 5 PE's per muon without wrapping, 11 PE's per channel after wrapping with either Mylar or Tyvek, and around 1.2 PE.s with sides blackened. The inferred calibration of PE's per ADC channel where generally consistent for all but the blackened sides experiment (i.e. around 40 ADC/PE; blackened sides gives 52 ADC/PE) which adds credibility to the results. This geometry is not the one we will use for the piop detectors, however. Generally decent fits to the Poisson shape (but this assumes all cosmic muons produce the same number of PEs, so ignores edge effects, low-energy muons...
2. Again, we confirm the fact that blackening sides does not help (matches qualitative results from GEANT 4)
3. Comparing the GEANT 4 simulations of this same geometry, we see a big discrepancy. Non-blackened, no-wrap simulation gives 77 PEs per muon, which is factor of 145 higher than data (and a factor of 7 higher than data with wrapping). Simulation with blackened sides gives 5 PEs per muon, factor of 4 higher than data. What is causing the big discrepancy?
4. Things to check: effect of low-energy muons (which might drop below Cherenkov threshold); does GEANT properly include the photocathode efficiency? Does the UV-cutoff for the PMT were are using match what is assumed in GEANT 4 (do we have a quartz or UVT window on the tube?). The acrylic used at U. Manitoba as UV-transparent. Could we be relying on lots of internal reflections (bounces), but maybe he surface roughness reduces the reflectivity?
5. To do: run with the detector oriented with respect to the cosmic rays similar to what we will use for the pion detector, compare results to GEANT4 in same geometry/orientation.

1. Adding Pb (2 cm) downstream of PMT in GEANT 4. Strange results - seems to reduce number of pions from pion generator (how? Do we have signal from pions bouncing back from materials downstream of the pion detectors? Need to investigate this). Also, need to run this with the beam generator, since the motivation was primarily to suppress the extra background seen (presumably from beam-dump or beam-pipe events) with the beam generator.