Sep 6, 2018 Calorimeter

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Meeting Time: 11:00 a.m.

  1. To join via a Web Browser, go to the page [1]
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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. BCAL and FCAL: Develop standard fiducial volume cuts for the calorimeters
  2. BCAL: Create non-linearity corrections for MC for gain adjustment. (Tegan) Work ongoing
  3. FCAL: Cross check MC changes by Richard to make sure that gains are not affected in both Geant3 and Geant4 (Collin) Matt/Sean are working with IHEP on calorimeter simulations
  4. BCAL: Interchange LED trigger cables and see if upstream and downstream features change (Elton and Mark)

Complete after new launch

  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.


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

Tentative Agenda

  1. Announcements
  2. Action Items
  3. Run Updates
    1. FCAL
    2. BCAL
  4. Calibrations
    1. Calibration Dashboard
    2. FCAL calibration using CompCal (Liping)
    3. PrimEx algorithm and calibrations (Ilya)
  5. Reconstruction and Simulation
    1. GlueX-doc-3737 SiPM Saturation (Elton)
    2. Update on Splitoff Rejection Studies (Rebecca)
      1. Previous work
  6. NIM articles
  7. Any other business


Attending: Elton, Colin, Liping, Ilya, Mark, Sasha (JLab); Matt, Rebecca (IU); George, Christina (Athens); Sean (FSU); Tolga, Rupesh (FIU); Will (CMU); Tegan, Colleen, Ahmed (UofR).

  1. Announcements
    • Accelerator is down till at least next Wed.
    • Christina asked if more detailed information could be made available to people offsite. Matt suggested participating in the first 10-15 min of the RC meetings (which are cancelled till Monday) to get latest updates from the accelerator. Elton: Will pass this along to RCs and suggest that more detailed/frequent e-mails be sent out to the collaboration.
  2. Action Items
    • Check MC gains in FCAL after updates by Richard. Matt: He and Sean have been meeting with IHEP, who have joined the collaboration and have expertise in calorimetry. They are seeing some anomalies in omega MC events. Will continue to investigate whether the effect they are seeing is only in the FCAL and its energy dependence.
  3. Run Updates
    1. FCAL (Colin)
      • Two bases have failed with about ten dropping HV. Twenty spares on hand. Waiting for accelerator news before additional replacements.
    2. BCAL (Elton)
      • Expect to take LED data today or tomorrow to address action item.
      • Spare chiller on the north side has been replaced with recently fixed chiller. Pressures are being checked and operation in preparation for the run. The north chiller is now out and can be used for the CompCal.
  4. Calibrations
    1. Calibration Dashboard
    2. BCAL pi0 (Tegan)
      • A small group met yesterday to review the plan for completion of the pi0 calibration in BCAL yesterday.
      • The first item is to check MC for gains and non-linearity with present code (no SiPM saturation), to be consistent with data processing to date (2016, 2017 and 2018).
      • Sean will generate the single particle gun MC events.
      • Will is providing scripts and guidance from previous work.
      • After completion of calibrations with no SiPM saturation, they will be repeated (i.e. checked) with the new code to simulate and correct for the SiPM non-linearity. (See below)
  5. Reconstruction and Simulation
    1. GlueX-doc-3737 SiPM Saturation (Elton)
      • This work has been reported before but is now summarized in the GlueX-doc. The code for simulation and reconstruction is on the elton_SiPM_saturation branches in halld_recon and halld_sim. It won't be merged until a consistent set of calibration constants are determined for 2018.
    2. Update on Splitoff Rejection Studies (Rebecca)
      • Update on ongoing work on the machine learning program to identify split-offs.
      • Differences between MC and data have been seen using exclusive omega events.
      • Using a different sample (inclusive pi0s) MC eff / Data efficiency is compared as a function of photon energy. It is seen that the ratio becomes smaller than one above for as the quality factor increases above ~0.5. The effect is more pronounced at lower photon energies.
      • Mark: May wish to test the performance with a more restrictive sample. Matt: Moved away from exclusive omega to avoid systematics.
      • Note: The quality factor is already stored in the REST files. Can be used for testing, but further checks are needed before it should be used in routine analysis.
      • Previous report of this work can be found at Barsotti_July27
  6. Calibration of FCAL using CompCal
    1. FCAL calibration using CompCal (Liping)
      • After calibration of the CompCal, consider using Compton Events to cross calibrate the FCAL. Both detectors are necessary for beam energies above 3 GeV.
      • Matt: For the eta Primakoff experiment, at high energies where efficiency ~10%, efficiency uncertainty will need to be ~0.1%. Liping: Possible using absolute normalization of Compton cross section on Be. Additional monitoring of 4He density will be needed.
      • Main concern is the calibration of inner blocks of FCAL that are poorly calibrated due to leakage. Matt: plan to run MC to determine pi0 mass in that region so that a proper calibration can be done, but manpower is needed to work on this.
      • Sasha volunteered to run MC, and Colin can provide cuts used in data, so they can also be consistently applied to MC.
      • Liping: Stability is another concern. Matt: LED data has been studied to check for calibration drifts, but interpretation is not straightforward. Nevertheless the data is available and can be analyzed in more detail.
    2. PrimEx algorithm and calibrations (Ilya)
      • Ilya showed how the calibration and analysis of the Hycal was completed, including energy and position calibration, non-linearities, and use of pi0's. Some of these methods might be useful for the FCAL and FCAL/CompCal combination.
  7. NIM articles
  8. Any other business