Mar 10, 2016 Calorimetry

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Video Conferencing Information

Meeting Time: 11:00 a.m.

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Participant Direct Lines

  • JLab Phone: in CC F326 is 757-269-6460 (usual room)
  • JLab Phone in CC L207 is 757-269-7084
  • 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. Update BCAL clusterizer to improve agreement between simulated and generated MC (Mark)
  2. Modify covariance matrix for FCAL and BCAL to correspond to the current resolution of the detectors (Matt).
  3. Change F250 simulation code to match firmware and add flexibility for new algorithms (Mike)


  1. FCAL HDFCAL log book
  2. BCAL HDBCAL log book
  3. BCAL Action Items and Working Tasks

Tentative Agenda

  1. Announcements
  2. Action Items:
  3. Run Preparations
    1. FCAL Update
    2. BCAL Update
  4. Reconstruction and Simulation
  5. Calibration
    1. Update on pi0 decay to e+e-g to extract energy resolution Will M
    2. BCAL - Update on Effective Velocities and Time Offsets - George
    3. Instabilities in the Integration of BCAL Pulses - Andrei
  6. Any other business


Attendees: Elton, Mark, Simon, Will, Ahmed (Jlab);Zisis, Tegan, Andrei (UofR); Sean (NW); George (Athens)

  1. Announcements
    • The refrigerator in accelerator was contaminated and repairs options were briefly discussed at the 1:30 planning meeting. However, immediately following the meeting, the CHL crashed and forced the decision to immediately start a week long CHL recovery and maintenance. Initial estimates of restoration of beam to Hall D is next Thu. More information is contained in the Arne's Elog 3390086
  2. Action Items:
  3. Run Preparations
    1. FCAL Update (update by Elton)
      • Jon and Adesh are currently replacing bases. Base failures continue at about 1 per day and weekly replacements keep dead channels in the data to about half a dozen.
      • Test setup at JLab is underway and should help timely diagnosis of failures and hopefully identify root causes.
    2. BCAL Update
      1. Mark: Event display hdview2 updated with extra window containing timing and z-information for the Bcal. Shows clusters on plot of z vs phi. Useful tool for understanding clusterizer.
        • Will has been working with Mark on identifying where the clusterizer is failing. The new event viewer is helping that effort. So far Will has been scanning MC single photon events to see how they fail. Clusters get split when the reconstructed z position is outside selection limits (DeltaZ > 15 cm). DeltaTime and DeltaPhi selections meet the criteria in the clusterizer. Need to dig deeper to understand the cause for the discrepancies in DeltaZ.
  4. Reconstruction and Simulation
  5. Calibration
    1. Update on pi0 decay to e+e-g to extract energy resolution Will M
      • Investigating the use of pi0->gamma e+e- events to determine the single photon energy resolution in the Bcal.
      • First set of slides are for inclusive pi0s. He finds several thousand pi0s per 200 MeV energy bin in about 800 files. We should have considerable more data.
      • Exclusive selection of gp->pi0p was also performed. Here only about 200 files were analyzed. Clear pi0 and eta peaks are seen with photons in either Fcal or Bcal. Fewer events found but situation is much more constrained.
      • Further studies are in progress, but it looks hopeful.
      • Sean: Suggests to look at the e/p distribution for the track other than the one which was selected.
    2. BCAL - Update on Effective Velocities and Time Offsets - George
      • George's summary of evolution of veff and time offsets using both cosmic ray and beam data
      • Looked at spring 2015 and spring 2016 data
      • New strategy for analysis relative to previous study: No DeltaZ selection cuts used to avoid bias
      • Finds cosmic rays give a veff~16.3-17.2 cm/ns, with the lower values corresponding to layer 1. But still some variation from channel to channel.
      • Production runs are much more stable, giving 16.4-16.5 cm/ns for layer 1. Layers 2-4 are consistent per layer, but values increase up to about 18.5 cm/ns for layer 4. It is believed the differences per layer is due to the spread of showers in the Bcal, and the results from layer 1 are a closer reflection of the veff in the module itself.
      • George's proposal is to upload values of veff from layer 1 for all layers into ccdb. Suggests setting DBCALGeometry::C_EFFECTIVE value: 16.45cm/ns. Discussion followed:
      • Mark: It appears the "true" value for the veff is given by the value in layer 1. However, its use in the reconstruction needs to account for the spread of the shower. Therefore its use in reconstruction should be evaluated. Possibly the measured values in other layers may result in a more consistent use in the analysis.
      • Elton: This analysis was completed with hadronic showers (mostly pions), but electromagnetic showers could be systematically different.
      • It was decided that George's analysis is complete, but we need to continue the discussion offline as to what to upload to ccdb and how to use the uploaded constants in reconstruction.
    3. Instabilities in the Integration of BCAL Pulses - Andrei
      • Uses cosmics mode 8 data to understand variations in the ratio of pulse integrals (26 samples)/(60 samples).
      • A principal culprit is incorrect assignment of the baseline (using the first 4 samples in the window).
      • A second reason for variation in the extracted energy is possibly the distortion of the shape of the pulses. Elton: Some of that distortion may be due to reflected pulses.
      • Using more samples for the pedestal alleviates the problem but does not solve it.
      • After correcting for the shape distortion the residual rms contribution from the pedestal is of order 3 MeV. These fluctuations are contributing to the measured pi0 mass resolution.
  6. Any other business