Nov 14, 2019 Calorimeter

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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


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

Goals for Calorimetry Group

  1. Determine preliminary photon reconstruction efficiencies as a function of E, phi and theta in data and simulation with a point-to-point precision of at least 5%.
  2. Measure systematics of pi0/eta mass calibration as a function of detector position to a precision of at east 5 MeV.
  3. Demonstrate agreement of photon reconstruction efficiency and resolution between data and simulation as a function of E, phi and theta to within 5%.

Action Items

Short term items:

  1. Take a new noise measurements of the BCAL FADC baselines (Mark and Jon)
  2. Evaluate effect of conversions in FCAL efficiency determination with particle gun and reactions (Richard suggestion -> Jon)
  3. Proposal for updating BCAL gain constants 2019 / extrapolation to higher energy (Karthik)
  4. Complete Calorimeter work packages

Long term items:

  1. From Mike's work: -cos(phi) type dependence in the data and a phi dependence at the downstream end of the bcal. See Sep 21, 2017 Calorimeter Meeting.
  2. FCAL: It has been noticed that the pi0 mass shifts when the LED pulser runs at high rate. This is still not understood. See Log Entry 3595928 and references. Several runs have been taken in raw mode. These runs exhibit the shift in pi0 mass with LED running at 1 kHz. There is a need to analyze these to try to determine the cause:
    1. 50634 - FCAL Green LED: 1kHz, 29 V, Livetime is 9%, 1.7 M events
    2. 50635 - FCAL Violet LED: 1kHz, 22 V, Livetime is 9%, 1.4 M events
    3. 50636 - FCAL Blue LED: 1kHz, 15 V, Livetime is 9%, 1.5 M events

Tentative Agenda

  1. Announcements
  2. Action Items
  3. Run Updates
    1. FCAL
    2. BCAL
  4. Calibrations
  5. Monitoring-
    • BCAL-LED update (Varun)[2]
  6. Efficiencies
  7. Simulations
    1. FCAL energy resolution
      1. 2% floor term
      2. 3% floor term
      3. 3.5% floor term
  8. NIM articles
  9. Any other business


Attending: Elton, Mark, Jon, Colin (JLab); Will (CMU); Churamani, Tolga (FIU); George, Christina (Athens); Karthik, Zisis, Varun, Ahmed (UofR); Matt (IU);

  1. Announcements
  2. Action Items
    • Jon: Effect of conversions on particle gun efficiency calculation. Checked one point with particle gun and it seems to account for the discrepancy between particle gun and reaction calculations.
    • Karthik: Has updated documentation on non-linear corrections, which will distribute shortly.
  3. Run Updates
    1. FCAL (Colin)
      • Should have sufficient tested bases in hand to swap out next week. Then will take LED data to investigate new firmware and make any HV adjustments.
      • Elton: At the RC meeting, Sasha mentioned has replaced 5 FADC boards in the FCAL. He is concerned that failures may be due to overheating and potentially the feedback system which adjusts the fan speeds. The causal connection for failures is circumstantial. The temperature feedback allows the readout thresholds to be lowered because the long period time shift of the baselines are minimized. Mark reminded us that at one time Tim installed some welding screens to cover the north BCAL crates from direct view of the hall A/C. For better cooling of cards one might also spread the FADCs apart so the are not packed all together.
    2. BCAL
      • Jon is learning how to process the checklist and it is now signed off. See response of single SiPMs in the plots below.
      • Single LED/SiPM test: 3735113 and 3740112
      • Need to take more data to investigate new firmware and check pedestal widths vs overvoltage. Data with the new firmware were taken but do not seem to process through the BCAL_online plugin. Sean: Could be that the plugin only checks physics triggers. [Note added: this was in fact the case and a mod has added to allow for a command-line argument to check LED triggers.]
  4. Calibrations
    • Mark: Inquired if Sean is waiting on any timing calibrations. It seems the necessary calibrations have been completed for the spring 2019 run.
  5. Monitoring-
    • BCAL-LED update (Varun)[3]
    • Varun walked us through some of the LED files taken in October with mod10 (raw data). Files were taken at 6, 6.25, 6.5, 6.75 and 7 V of LED bias to assess the optimum for LED data for the upcoming runs. The nominal value of 6.25 V seems to be ok. It was shown that the number of triggers processed decreased with increasing voltage. The hypothesis is that this is due to missing events that overflow, but it was not clear why these would not be included into the histograms. Elton: Also need to check for missing events with low pulse heights at the low LED bias voltages.
    • Ahmed: The LED analysis code, running for several years, is now checked into GitHub.
  6. Efficiencies
  7. Simulations
    1. FCAL energy resolution
      • Mark has run MC for gp->pi+pi-eta, eta->gg. Assuming the contribution due to position resolution is small, the eta width can be used to extract the energy resolution DeltaE/E. For the BCAL, data and MC are in fair agreement. For The FCAL, Mark has run MC with various values of resolution parameters in mcsmear.
      • 2% floor term
      • 3% floor term
      • 3.5% floor term
      • A few combinations of the constants agreed with the data in the available energy range. It was decided to pick the parameters 0.05/sqrt(E) and 0.03 for the stochastic and constant terms to put into mcsmear. A new constant would be added to ccdb:/FCAL/MC/energy_width_floor. Further studies will be needed to determine the precise values of each constant separately.
  8. NIM articles
    • Matt will read the section on calorimeters and add a paragraph on clustering.
  9. Any other business
    • Note that two weeks from now is Thanksgiving, i.e. no meeting.