Apr 4, 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. Complete Calorimeter work packages
    1. Item #3 (done), add link to work summary (Colin) Links added to various plots.
  2. BCAL. Remove BCAL LED triggers from monitoring occupancy plots. (Sean)
  3. FCAL/BCAL. Check that Richard has adjusted Geant4 constants to match Geant3. (Sean)
    • Richard: BCAL/BCAL parameters have been tuned. The gain in hdgeant4 is unity and hdgeant has been adjusted to match. For FCAL, hadronic response still needs work. Response to the light guide is available but not used in mcsmear yet.
    • Matt: Adjusting parameters in mcsmear (now the hdgeant is set) awaits 1) tuning of non-linear corrections using particle gun 2) Rebecca will tune threshold response at low energy, which affects pedestals and makes a difference to neural net response. Next up: checking resolution and hadronic response including response in the light guide.

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
  6. NIM articles
  7. Simulations
  8. Any other business


Attending: Elton, Colin, Sean, Mark (JLab); Ahmed, Tegan, Zisis (UofR); Matt, Jon (IU); Curtis, Will (CMU).

  1. Announcements
  2. Action Items
    1. Reviewed work packages. Any updates should be reflected into the table, including links to relevant work.
      • Tolga: Interested in working on timing for neutrals. Will connect with Elton and Mark when his schedule clears.
    2. Notes on other action items noted above.
  3. Run Updates
    1. FCAL
      • Three bases replaced this week. Stable since then. Communication issues continue at a low level.
    2. BCAL
      • Mark: Occupancy plots look ragged. Pedestals adjustment did not fix this issue.
      • Sean: What is the status of 4 ns offsets? Mark: Code needs to be developed. Waiting on pressure from Primex group. Sean: See hadronic background in eta Primakoff production and are using BCAL to help veto incoherent background.
  4. Calibrations
    • BCAL Gains Fall 2018 (Elton for Karthik while he is on shift)
    • Calibrations have been completed for pixel/count of 0.25 and 0.3, with the best value being 0.25.
    • Extrapolation to higher energy is an issue and need to anchor the projection to avoid overcorrecting.
    • Zisis: Reminded everyone that leakage studies were completed many years ago (reported in BCAL NIM article), which show the components of leakage as a function of energy for 3 different angles. (see also Fig 8 in GlueX-doc-1871)
    • Richard: In his single-photon studies he sees non-linearities, which are z (or theta) dependent. See slides below.
  5. Monitoring
    • BCAL-LED-Trigger-Quadrants - Foda
    • Objective is to revise and specify revised skim conditions.
    • Elton: suggestion is to select LED events by taking Nhits > 1200.
    • Sean: For monitoring, we wish to exclude LED events from plots. Mark: Suggestion is to eliminate E<12 GeV. Ahmed will generate energy distributions from data to check validity of selection.
  6. NIM articles
  7. Simulations
    1. Good agreement between hdgeant and hdgeant4, for both FCAL and BCAL
    2. FCAL: Extend study of reconstructed vs generated energies out to E=8 GeV.
      • FCAL timing: Subtracted flight time from distributions. However, finds time offset increases from about zero at E=0 linearly up to 0.45 ns for E=8 GeV. It is unclear what the source of time walk is. This seems to have change since Matt looked at it. Cause of change is unclear.
      • Sean: MC and Data are calibrated differently No calibrations for MC, which default to data in ccdb. ccdb has not been updated for a long time.
    3. BCAL: Extend studies also out to 8 GeV. Non-linearities of < 1%, except for angles above about 60 degrees where leakage out the back can lead to 2-3% corrections.
      • BCAL : Timing offsets of up to 50-60 ps found in MC, varying with energy. Sean: Need to analyze data/MC in the same way to evaluate discrepancies.
      • BCAL: Tags of up and down hits propagated to the ends of the BCAL ("end" tags) were deprecated. They are now available and could be used in mcsmear to reconstruct times. It was agreed these are a better representation of reality than the hits at production points. They need to be incorporated into the mcsmear routines.
      • BCAL: Should one use energy weighted (Richard: now used by default for FCAL and BCAL) or earliest time? Mark: Earliest time might be best. Elton: Earliest time should be used with some threshold. After some discussion, the consensus was that energy weighted might be ok since light reflections in the modules are not implemented.
  8. Any other business