SoLID Ecal Weekly 20230803

Update from Carter on Timing

• Reminder: SC_C - SC_D yields about 450ps. Rough estimate based on scintillator thickness gives about 210ps for C-D. So we are ~ factor 2 off (assuming similar PMT TTS as HRS S2 and S2m)
• (T+B)/2 for LASPD minus SC_C (or minus SC_D) gives about 750ps in sigma, or under 700ps with tight tracking cuts in x. If using 150ps (LASPD) plus 62.5ps (edge finding) plus 450ps/sqrt(2) (for either C or D alone), we expect 340ps. So we are factor 2 off.
• (T+B)/2 for LASPD minus (SC_C+SC_D)/2 gives about 760 in sigma without cut, and 660 -> 650 -> 575 ps with increasingly tight position cuts. (SC-C size, quarter SC-C size, left-side with high GEM efficiency). Q: Would taking (SC_C+SC_D)/2 reduce the resolution by sqrt(2), if C and D have the same resolution?
• discussion of drift distance: C (56.2mm) LASPD (68.9mm) D so total about 150mm from C to D counting LASPD thickness (2cm). So taking (C+D)/2 would be roughly the hit time on the LASPD, though the drift time for most GeV-level particles would be minuscule.
• Suggested to do: try all combinations of T, B and minus C, D, to see what the sigma value is. Note that if plotting T or B alone, need to place tight position cut (present cuts are okay). Then choose the combination with the smallest sigma vs y to see if there is any correlation to be corrected.

Tuesday 8/1 Slides

Update from Darren on ML PID

• Darren's Tuesday 8/1 Slides, summary:
  • with higher statistics for background, completed beamtest sim + bg (x1, x10) ML study. Typical charged pion rej is 1E3 and typical pi0 rejection is 8-10, both at an electron efficiency of 95%. The "pi0 vs. e" (corresponding to 2x2 matrix, matrix not shown) and the "pi+/-, pi0, e" (3x3) show similar results for pi0, though the 3x3 matrix is slightly worse.
  • studied TS1,
• To do: Given the limited time left, will focus on getting the new pi0 simulation read correctly
• Moving forward regarding applying ML to actual data -- Darren will give the code to Zhiwen. Two possibilities:
  • use the "clean high-energy e sample" and "clean pi0 sample" (from Ye) and "clean pion sample" (from Mike) to both train and test the ML, but this may not be worth doing because we expect "high performance".
  • use the ML classifier trained by beam test sim + bg on the two clean samples and see how they work.
  • use the ML classifier trained by beam test sim + bg on the full data set and see how they work.
• Darren's Thursday 8/5 Slides, summary:
  • completed all tasks from Tuesday.
• Darren also tried looking at "clean" electron and "clean" charged pion samples provided by Ye and Mike. Looks like electrons are fairly clean but pion samples have significant contamination. Discussions:
  • Simulation did include "delta electrons" (Ye)
  • Need to use simulation to help cleaning up charged pion sample,
  • Alternatively, we should use simulation to determine electron/pion "contamination" in charge pion/electron sample so we can correct for it.
  • These samples used TS4, but ML only trained on simulated TS1 and TS3, do we need to train another classifier for TS4 before applying them to data? (this needs to be done by Zhiwen)

• Recall we still need:
  • classicial PID results using beamtest simulation + bg (Spencer)
  • classical PID for pi0 using TS1 and TS3 (Ye)
  • possible pi0 samples from data (Ye)

Update from Ye on sim

From simulation meeting:

• eAll code used phi (should be cos(phi)) for event generation. This is missing sin(phi) factor and resulting in higher yield than the correct value. The difference is small at forward angles -- sin(phi)/phi, but large for phi close to 90deg. For PVDIS configuration, 22-35 deg, the rates are 30% higher (than real value). This eAll sim was used in all 2022 PVDIS impact studies, including PDF dependence and 11 vs. 22 GeV comparison, as well as BNSSA proposal. However, note that the study also missed radiative factor which would cause rates to be 10-20% higher (due to resonances having higher rates). So effects on the rate estimation is at 10-20%.

Update on sim/data comparison and rate-dependence

• Mike showed MIP peak shifts of high rate runs for Shower-R, shifts is systematic and relatively "clean"
  • need to make the same plot for Shower-L and Shower-T
  • also studying pulse H vs. Int vs. W
• Ye showed TS4 Shower spectra dependence on beam current and day of the run. There were two problems, noted below along with discussions:
  • slide ??: Two runs both at 5 (10?) uA showed clear MIP shifts by 20%. Question: were there any changes in hall setup that could cause e.g. different stray field from the spectrometers?
  • slide ??: With TS4 high threshold runs, spectra showed not only the threshold position increases, but also the absolute (event count/time) increases more than beam current does.
  • is it gain change? (Paul thinks so)
  • could be baseline shifts causing systematic increase in MIP pulse integration (Xiaochao thinks so but needs simple MC backup)

General discussions

• CLAS12 use pion events for real-time calibration (cosmic wouldn't work and MIP shifts when the magnets are turned on). JP: We should always use pion events in physics runs, along with momentum information of electrons.