Mar 7, 2019 Calorimeter

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Meeting Time: 11:00 a.m.

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  • 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
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  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. BCAL: Check pulsing rate of LED triggers when FP trigger bit is missing (start with early runs in fall 2018). With discerning software, check pulsing rate of later runs where it appeared that the downstream FP LED bit was not firing. (Ahmed)
  2. BCAL: Check that latest gain ratios are uploaded for spring 2018 (Mark).

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. Reconstruction and Simulation
  6. Monitoring
  7. NIM articles
  8. Any other business

Tolga: The Pedestal code is located here, modifications to FCAL_online plugin: /w/halld-scifs17exp/terbora/ It is broken now, but I am making corrections as I speak and the file will be cloned there as I go.


Attending: Richard (UConn); Ahmed, Zisis, Tegan (Regina); Curtis, Will (CMU); George (Athens); Matt (IU); Tolga (FIU).

  1. Announcements
  2. Action Items
    1. Tolga: Will briefly update on FCAL pedestal code project for group's information. Was focused on later agenda item so I did not produce updated plots today. Talk:
      • Reviewed some plots obtained from pedestal and occupancy plots for FCAL. There were several questions and it was suggested that Tolga send specific information regarding the production and scripts to obtain the plots.
  3. Run Updates
    1. FCAL
      • Standard maintenance. Failure rate is about 2-3/week of bases that die. Other failures (communication) fell from last fall att 1/day -> 1/week.
    2. BCAL
      • Pedestals seemed non-uniform and Serguei has taken a new run. We are waiting to see how the BCAL will be used in PRIMEX to understand the calibration effort needed for this period. It may be that only 4ns shift calibration will be needed. Although, Mark uses tracking for that calibration and no drift chambers are currently being read out.
  4. Calibrations
  5. Reconstruction and Simulation
    1. GlueX-doc-3852 HDGeant, HDGeant4 cal systematics (Richard)
      • Richard repeated his study of MC showers from hdgeant3 and hdgeant4 in FCAL and BCAL and compared to generated. The updated plots use fitted Gaussians to slices instead of profile histograms, which use means and rms. There was generally good agreement between hdgeant3 and hdgeant4 (<~ 1%)
      • Both FCAL and BCAL returned about 30 MeV less in the reconstructed compared to generated energies.
      • Small gain shifts were observed in BCAL (~1%) and FCAL (~0.5%). Differences in the FCAL gain between hdgeant3 and hdgean4 were tuned to zero with hdgeant4 parameter. This could also be done for BCAL. Mark would like to investigate the effects in BCAL before any changes. Absolute agreement between reconstructed and generated values can also be tuned. Richard will do this for FCAL.
      • Main effect was about a 30 MeV shift in reconstructed energy relative to generated.
    2. The work above should be reconciled with this log entry: [3]
      • Matt: Richard's results seem to be qualitatively consistent with information in this log entry.
      • It was decided to go ahead and put in a new non-linearity correction into CCDB, although the reason for the change is not understood.
      • Colin: New gain calibrations will have an effect on the simulation of the readout thresholds and might lead to changes in the non-linearity.
      • Sean: Richard's data only go up to 2 GeV and it would be good to extend it to higher energies (e.g. calibrations to up to 3.5 GeV).
      • Mark: Notes that the BCAL may also want to set MC thresholds based on measured gains.
    3. Tolga: Wants to discuss if reopening photon/neutron separation analysis is viable to potentially study calorimeter response for a couple neutral channels that I am looking at. Slides:
      • Investigating the following two reactions: gp->pi+ p pbar n and gp-> pi- p p nbar.
      • Matt: Reconstruct reaction with missing n and check data to see if there are energy signatures in the direction of missing neutron.
      • Sean: Start with a sample of clean neutrons, e.g. gp->npi+ and reproduce/compare to original study by Justin.
      • Mark: neutron/photon discrimination is technically difficult. Should start asking 1) how much discrimination is needed for your channel? and 2) given the energy distribution (i.e. distribution of speed of neutrons) how much help could be expected from direct detection?
      • Mark: In the plots recommends plotting measured instead of fitted values.
      • Tolga poled the group as to the benefit of investigating direct neutron detection.
    4. GlueX-doc-3875 Cal Efficiency using the CosThe Method (Elton)
      • Slides from the Costhe efficiency method were updated since the last meeting. Uses photons from pi0 decay in gp-> omega p -> pi+pi-pi0, pi0->gg with a constraint on the pi0 mass.
      • Comparisons were made between data and MC distributions. The most prominent feature is a unphysical peak in FCAL (and FCAL/BCAL distributions) near costhe*~ 1. There are very asymmetric decays and likely due to detecting the single high energy photon (from the pi0) and combining it with a large number of low energy (uncorrelated) showers.
      • Mark: The MC should reproduce the peak if it is due to uncorrelated low energy hits, which are now included into the simulations by default. Matt: This could be due to differences in simulated showers, but also a difference between data and MC Chi2 distributions.
      • Elton also showed initial results of using the IHEP method, where pi0 energies are not constrained and the efficiencies are obtained by dividing the weighted E2 energy distributions by the distribution which is not weighted. This can be used for systematic comparisons with the other method (that requires knowledge of the pi0 momenta). Elton and Qiao plan to write up the study for reference once the studies are complete.
      • Matt: Suggests to clearly label efficiencies on these plots as "relative efficiencies."
  6. Monitoring
  7. NIM articles
  8. Any other business

Tolga: The Pedestal code is located here, modifications to FCAL_online plugin: /w/halld-scifs17exp/terbora/ It is broken now, but I am making corrections as I speak and the file will be cloned there as I go.