Apr 6, 2017 Calorimeter

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Video Conferencing Information

Meeting Time: 11:00 a.m.

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Participant Direct Lines

  • JLab Phone in CC L207 is 757-269-7084 (usual room)
  • JLab Phone: in CC F326 is 757-269-6460
  • Phone in the Regina Video-conference Suite is 306-585-4204
  • Athens Phone: in Christina's office is 011-30-210-727-6947

Action Items

  1. Determine number of saturation/underflows that exist in the two LED bias monitoring settings (Ahmed) Working on periods with only one bias
  2. Understand the nature of the peak in the (Fcal propagated to target -RF) satellite peak of -2 ns (Adesh) Under investigation. Will use LED data to investigate this and 4 ns shift in fADCs
  3. Disable red LED string in dark room to avoid leaving it on in the future. (Adesh)
  4. Quantify the LED pulser sector jumps within one run (Ahmed) Investigation of outliers continues under study.


  1. FCAL HDFCAL log book
  2. BCAL HDBCAL log book

Tentative Agenda

  1. Announcements
  2. Collaboration Meeting May 15-17, 2017
  3. Action Items
  4. Activities during the down
  5. FCAL update
  6. BCAL update
  7. Calibrations
    1. BCAL gain calib (Will M.)
    2. ADC timing: 4 ns run-to-run shifts in certain BCAL channels
    3. BCAL gain drifts: Spring 2017 all runs
  8. Reconstruction and Simulation
  9. NIM articles
  10. Any other business


Attendees: Elton, Adesh, Mark (JLab); Sean (NW); Will (CMU); Andrei, Zisis, Ahmed (UofR); Matt (IU); Christina (Athens)

  1. Announcements
  2. Collaboration Meeting May 15-17, 2017
  3. Action Items
  4. Most items are under study.
  5. Activities during the down
    • Adesh will talk to Fernando/Chris/Nick about disabling red light option in Fcal dark room.
  6. FCAL update (Adesh)
    1. Pi0 gain calibrations have been completed for spring 2017
      • CCDB has been updated with new calibration constants
      • See a rate dependence to the gain calibration. The periods with low intensity show a pi0 peak at 130 MeV after calibration. Pedestals for these periods are fine. Will investigate with LED data.
      • Non-linearity correction has been determined. A single curve function will do. (2016 data seemed to require a linear and curve function.
    2. Timing
      • Satellite peaks at 2 ns are not understood.
      • One also sees a time slewing, but the source is unclear. The slewing seems more pronounced when one uses pi0 calibration showers.
      • 4ns shifts in fADC channels have not been established. The plan is to look at LED data. Ahmed: any time shifts are at the percent level, but Sean noted that other systems see a wider issue.
  7. BCAL update
  8. Calibrations
    1. ADC timing: 4 ns run-to-run shifts in certain BCAL channels (Mark)
      • Extracted 4 ns shifts channel by channel as a function of run number. This is done by comparing ADC and TDC data.
      • Some channels actually see shifts in both directions (i.e. 3 peaks)
      • The 4 ns shifts affect the extraction of higher level constants, i.e. gain ratio and attenuation lengths.
      • Expects to commit code and tables for the 4 ns shifts later today
      • The present method does not work for layer 4 because there are no TDCs on layer 4. Need to develop another procedure for layer 4.
    2. BCAL gain drifts: Spring 2017 all runs (Mark)
      • Plot ln(ADC_up/ADC_down) vs z to extract gain ratio and attenuation lengths.
      • These constants have been determined before the 4 ns shifts, but they are affected by the timing shits, so need to be redone after the 4 ns shifts are corrected.
      • Gain ratios are seen to vary as a function of run number for some channels.
    3. Stability of LED signal vs rum number for problematic channels (Ahmed)
      • Ahmed has confirmed that channels identified by Mark have poor stability. The stability is a problem for one side, usually the channel with lowest gain
      • It has not been decided how to handle these problematic channels. So far about a dozen have been identified.
      • Will also finds that the problematic channels are showing poor calibrations, which is not surprising since their gain is time dependent.
      • Zisis: Could this be due to the summing circuit? Mark: No clear systematics has been found yet.
      • Andrei: Do the channels show the same behavior at lower bias? Elton: we have been running at Vover=1.4 for over a year and have not investigated long term stability at other settings.
    4. BCAL gain calib (Will M.)
      • Started with flat gains and gain ratios from Mark
      • Found no improvement after 5 iterations. It is unclear why last years matrix inversion procedure is not converging.
      • Tried removing the B mass constraint. No improvement
      • Looked at pi0 mass vs channel number for channels contribution more than 50% of energy to a given shower.
      • Removing the B mass constraint and using tight eigenvalue selections, gain changes seemed to follow pi0 mass, so improvements made sense and helped.
      • Further improvements were clearly possible, so use sort(mean/pi0 mean) to move gains toward improved pi0 mass for showers with >50% of shower energy. This improved resolution considerably. However only seems to work for layers 1 and 2, which has substantial statistics.
      • Went back to matrix inversion method for other layers, but little improvement is seen.
      • Zisis: Could one use Andrei's cosmic-ray calibrations?
      • Mark: What fraction of statistics is included in this calibration? Will: About 5%. Mark: Perhaps one can skim events with energies in layers 3 and 4. Will: May still need to relax the fraction of energy required in a given layer to probe layers 3 and 4.
      • The final result shows lower pi0 widths than 2016 and the gain constants are more tightly grouped than before. It was always surprising that the 2016 gains had such a large variation.
      • Mark: Could the 2016 data benefit from the current set of constants? will: Perhaps and will check that
    5. Non linear corrections (Will)
      • Finally, first look at non-linear corrections in 2017. Shape of correction different than last year.
      • Need to consider best fit function. Variations from pi0 mass after corrections are less than 0.5%
      • Sean: It would be interesting to study the systematics after all corrections.
      • pi0 data extends only up to about 3 GeV. Perhaps can use J/Psi and/or high energy electrons to extend / test corrections to higher energies.
      • Discussion: Will should go ahead and put the current version of the gain constants in ccdb so that calibration launches can benefit from them.
  9. Reconstruction and Simulation
  10. NIM articles
    1. Bcal: Zisis has updates to the paper. Now needs input from Mark, Will and others for sections that they are working on.
  11. Any other business