BCAL Reconstruction Meeting 2015-07-09

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Video Conferencing Information

Meeting Time: 11:15 a.m. EDT

  1. To join via a Web Browser, go to the page [1] https://bluejeans.com/907185247.
  2. To join via Polycom room system go to the IP Address: (bjn.vc) and enter the meeting ID: 907185247.
  3. To join via phone, use one of the following numbers and the Conference ID: 907185247.
    • US or Canada: +1 408 740 7256 or
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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


  1. BCAL Reconstruction Issues
  2. BCAL Reconstruction Algorithms
  3. Will's reconstructed energy info

Action Items

  1. High priority items
    1. BCAL and FCAL z coordinates: some are referenced to the center of the target, not the global coordinate system.
  2. Low priority items
    1. z-coordinate determination from up/down amplitude ratio
    2. Sampling fraction tables
    3. Code Cleanup


  1. Announcements
  2. Action Items
  3. Commissioning Efforts
    1. Time-walk corrections (Noemi)
    2. Layer efficiencies (Ahmed)
  4. Simulations
    1. Single-energy code (Tegan)
    2. Cosmics (Andrei)
  5. Reconstruction
    1. Shower curvature (Tegan, Andrei)
    2. pi0 mass and gamma reconstruction
    3. BCAL Clusterization (Will M.)
  6. Any other business


Attendees: Elton, Mark, David (JLab); Tegan, Ahmed, Noemi (UofR); Will, Mike (CMU); Sean (NW).

  1. Announcements
    • Eugene and Curtis are collecting info for the S&T review. Thanks to Will for providing status updates.
  2. Action Items
  3. Commissioning Efforts
    1. Time-walk corrections (Noemi)
      • Updated versions of the software have caused delays and there is still some confusion about the output of some programs.
      • Noemi will send an e-mail to Mark and Elton with details so that we can better respond to the specifics
      • After studying the time-walk for generated pulses, Noemi is now turning to data
      • Mark: Should find data samples that cover a relatively large range of pulse heights. It would be useful to find data runs of physics running, cosmic-rays and LED pulser runs. The physics data should have a good spread of pulse heights. The cosmic-ray data is limited in the range of pulse heights (at least for tracks normal to the BCAL). The LED pulser runs are usually taken at a fixed LED bias setting, but there are a few that span the range of pulse heights that can be used for this study.
      • Elton: Plot the TDC_time - ADC_time vs pulse height (or integral). The behavior should reflect the time-walk in the TDC measurement.
    2. Layer efficiencies (Ahmed)
      • Investigating differences between BCAL efficiencies in mode 7 and mode 8 data.
      • Found that the point energies for mode 7 have a negative tail (at the percent level), but not so for mode 8.
      • Mark: The negative tail is likely due to late pulses, which extend beyond the end of the window, have a full pedestal (of 60 samples) subtracted. This can lead to negative numbers in mode 7, while the situation is handled correctly for mode 8. In the long term, one can change the F250 firmware to account for this. In the meantime, one can check that the negative pulse heights indeed correspond to late times and remove them from the analysis.
      • [Note added] Elton has added this issue to the F250 firmware discussion so it won't be forgotten.
      • Do the underflows affect efficiency? This can be checked once the negative hits are eliminated with a timing cut.
      • Efficiency plots for R3182 show a phi modulation especially in layer 4. Mark: Check the trigger for this run, there could be significant cosmics in the data stream causing the modulation.
      • Inconsistencies found in comparing hdview2 with BCAL_Eff: a) showers without tracks b) tracks without showers. Elton: Check that hdview2 and running BCAL_Eff are accomplished with all the same inputs, ie. Bfield map and ccdb version.
      • Discussion about adding BCAL information to hdview2 to help debugging. Will and Mike have asked Simon to add z information to the display. [Note added: I asked Simon. He says that he has thought about this, but it is unclear how to display the z information effectively. Recall that the display has a cut view, so the projection of the z position could appear anywhere inside the volume of the detector. He does note that you can turn on the shower projection hits, which may be a surrogate]
  4. Simulations
    1. Single-energy code (Tegan)
      • Goal is to add code for the MC to create digiHits, which could then be calibrated using the pi0 gain calibration, similar to real data.
      • Tegan sent an e-mail to David and is waiting a response.
    2. Cosmics (Andrei)
      • Tegan is searching through the run archive to provide as much statistics as possible to Andrei
  5. Reconstruction
    1. Shower curvature (Tegan, Andrei)
      • Using generated shower shapes to optimize clusterizer.
      • First modifications increase the width in z (deltaZ) that include hits into a cluster at smaller angles. This has a similar effect as the IU clusterizer, which uses polar angles for selection.
      • This new code tries to all hits for a shower, but needs an initial guess for the energy and angle of the shower, which it takes from the original clusterizer.
      • We need to find a good way to validate any code changes. Zisis suggested looking at pi0 peak as a way to checking whether it improves reconstruction.
      • Mark: Suggestion to make plots to demonstrate any problems, then consider the best way to address them. Note that Will is also working on the clusterizing algorithm.
    2. pi0 mass and gamma reconstruction
      • Noted that the up/down gain ratios that are being used come from the fall data and have not been updated.
      • Mark obtained the constants, but wants to streamline the code so that it can be integrated into the monitoring system.
    3. BCAL Clusterization (Will M.)
      • Finding that there are showers that are fragmented due to using the incorrect vertex location (center of target). Using a tracking vertex may fix the problem, but may be an effort
      • Very small fraction of events
      • Elton: General comments: a) even if the fraction of events is small, it may correspond to an interesting sample. b) it is good to have clusterizer be independent of tracking at least in a first stage. However, having a second stage that requires tracking may be useful or desirable
      • Will will study this in more detail to inform a decision as to whether and how to improve the analyses of these showers.
      • Single-ended hits. Investigating how single-ended hits affect shower energy and will make plots to show next week.
  6. Any other business
    1. Sean: Has there been any progress on understanding how energy is propagated through mcsmear? Elton: The latest MC energy plots from Tegan are consistent with losses due to leakage. In discussions with David it was decided to have the MC produce digiHits, which can be analyzed like real data to use gain factors from ccdb.
    2. Mike: At the last calibration meeting, some monitoring plots that match tracking to the BCAL appear inefficient for a range with low module numbers. Elton does not see this in the BCAL_Eff rate plots. There is a suspicion that it may be due to inefficiencies in the CDC, but specific correlations have not been made yet.