Nov 15, 2018 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

Action Items

  1. FCAL: Cross check MC changes by Richard to make sure that gains are not affected in both Geant3 and Geant4 (Matt/IHEP)
  2. Fix FCAL online monitoring plugin to properly plot low level digi quantities in 2D displays. 2D display of pedestal is hard to get because occupancy plot is filled in a different loop. (Tolga)

Check:

  1. From Mike Staib'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.

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%.

References

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

Tentative Agenda

  1. Announcements
    • (Elton) One week of data at low energy (coherent peak at 7 GeV, PS set for 3-5.5 GeV) and low current (40 nA) to check cross sections. Settings are set back to nominal (8.82 GeV coherent peak). Expect to run through Thanksgiving to complete the first GlueX experiment. The accelerator will be down for 3 days to lower energy to 10 GeV and concurrently, Hall D will install the CompCal in preparation for commissioning.
  2. Action Items
    1. Tolga: Has downloaded the relevant scripts. Too many events to run via remote login. The structure of the JEventProcessor is similar to plugins, which he is familiar with. Plan to extract pedestals into arrays for processing instead of manipulating histograms. Expect preliminary figures soon.
  3. Run Updates
    1. FCAL (Colin)
      • Last 2.5 weeks has seen a drop in dead basis, down to about 2-3/week and is manageable. This may be due to identifying bases with communication issues, which can be fixed by recycling HV. The lower failures may be due to lower intensities of recent running period.
      • Checking signals on some of the inner bases to be ready for CompCal.
    2. BCAL
      • Recently found that the pulser system stopped working for the downstream LED. This was fixed by stopping the pulsing sequence and setting 'continuous' mode by hand for both upstream and downstream. See Log Entry 3626205.
      • Based on online monitoring plots, we see that BCAL and FCAL pi0 calibrations seem to be fairly stable.
      • (Zisis) Ahmed has checked the new pulsing scheme and finds everything in order. Elton: It would be good to have an update at the next meeting, showing average stability over time as well as identification of channels with anomalous behavior.
  4. Calibrations
    1. BCAL timing: Mark has calibrated the BCAL timing offsets up to run up to run 51377.
    2. Non linear corrections for pi0 gain_calibrations for the BCAL: An Update File:Non linear corrections update.pdf.
      • Elton comment: Karthik has learned the pi0 calibration process from Tegan and is implementing it on the 2017 data for comparison with Tegan's results. The plan was to use the SiPM saturation code. Initially, Karthik had a branch checked out but it seemed to contain the master files. Once this was fixed, Karthik has started iterating the calibration and constants are indeed changing from before, but converging based on two iterations.
      • (Zisis reported for Karthik who is on shift). Non-linear corrections at each stage are apparent with the new SiPM saturation code, but we expect to reduce the final non-linearity after gains are adjusted to the pi0 mass.
  5. Reconstruction and Simulation
    1. Log Entry 3621347 FCAL Non-linear Response in MC (Matt)
      • The current non-linearity corrections in the MC do not seem to match the data. It is unclear what has changed, although Richard did implement a change to HDgeant and HDgeant4 that should have been neutral in terms of gain change.
      • Matt has sufficient MC to find new corrections. Sean: It would be nice to find the origin of changes since the last determination of the non-linearity corrections. Why has this changed? Sean: Also, it could be that the impact of thresholds may change if gains are changed.
  6. Monitoring
    1. Radiation Damage in Inner Blocks of FCAL and Image of all inner blocks
      • (Colin working with Jared) There have been further studies of the Radiation Damage of blocks per channel around the beam hole.
      • Relative light output of LED pulser is shown plotted vs sequential numbers related to run number on a normalized scale of 60-100%. The response decreases for higher run numbers with the slopes increasing from green to blue to violet, as expected for radiation damage. Also, the blocks on the corners (farther from the beam centerline) are least affected.
      • The row below the beam line seems the most degradation. This is the region that also sees larger counting rates. This may be due alignment of the FCAL relative to the beam (note that the beam is centered vertically as determined by the drift chambers), asymmetry of magnetic field due to more iron at the bottom of the detector (affecting low energy particles), or other effects.
      • Various anomalies are seen for some blocks, including large spread between colors, saw toothed jumps in response, changes in the slope of degradation, etc. Some of these may be due to changes of bases during the period, changes of slopes may be due to the way plots are presented. Causes are being investigated further.
      • Note that the pi0 mass peak is not visible for these channels using the nominal reconstruction.
    2. Elton: Is specific work being completed in preparation for CompCal commissioning? Colin: Efforts to raise the gain of some of these PMTs was attempted earlier, but several are pegged at the administrative limit of 1800 V. Matt: Lack of Peak in these channels is likely not caused by degradation in radiation, but perhaps due to high rates. CompCal will run at lower rates, so this might help identify the pi0 peak above background. Colin: Ilya has started looking at the reconstructions starting from hits (instead of showers) in the FCAL and claims that a pi0 peak has been seen. The algorithm is derived from experience with HyCal. This effort is ongoing and hopefully will be helped by lower rates during commissioning.
  7. NIM articles
  8. Any other business

Minutes

Attending: Elton, Colin (JLab); Will (CMU); Tolga (FIU); Zisis, Tegan (UofR); Sean (FSU); Matt (IU).

  1. Announcements
  2. Action Items
  3. Run Updates
    1. FCAL
    2. BCAL
  4. Calibrations
    1. BCAL timing: Mark has calibrated the BCAL timing offsets up to run up to run 51377.
    2. Non linear corrections for pi0 gain_calibrations for the BCAL: An Update File:Non linear corrections update.pdf.
  5. Reconstruction and Simulation
    1. Log Entry 3621347 FCAL Non-linear Response in MC (Matt)
  6. Monitoring
    1. Radiation Damage in Inner Blocks of FCAL
      1. Image of all inner blocks
  7. NIM articles
  8. Any other business