HDGeant4 Meeting, April 6, 2021

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HDGeant4 Meeting
Tuesday, April 6, 2021
3:00 pm EDT
BlueJeans: 968 592 007


  1. Announcements
  2. Review of minutes from the last meeting (all)
  3. Issues on GitHub
  4. Pull Requests on GitHub
  5. Action Item Review


Present: Tegan Beattie, Mark Ito (chair), Richard Jones, Zisis Papandreou, Lubomir Pentchev, Simon Taylor, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site. Log into the BlueJeans site first to gain access (use your JLab credentials).

Review of minutes from the last meeting

We went over the minutes from the meeting on March 23rd. Richard suggested we close Issue #181, "G3/G4 Difference in FDC wire efficiency at the cell boundary" as an HDGeant4 issue and re-open the remaining work to get data/MC agreement as a halld_sim issue, specifically one with mcsmear, now that our various simulation engines agree with one another.

Issues on GitHub

Proton timing in the BCAL

On Issue #179 Tegan presented further work using the test branch of HDGeant4 Richard provided that supplies parent particle information. Armed with this new tool he showed some new plots (APR02_ProtonComparison.pdf) with a proton particle gun aimed at the BCAL. Each slides has plots for G4, G4-NHL, G3-HADR1, and G3-HADR4.

  • slide 12: Photon production mechanism vs. time.
  • slide 20: Photon production mechanism vs. parent particle ID
  • slide 10: Photon, positron, electron, and pi+ production times
  • slide 8: Photon, positron, electron, and pi+ energy spectra

The overall conclusion from the Tegan's study is that G3-HADR1 is the one model that shows a long, late timing tail (slide 3), even though the plot from Lubomir linked at the beginning of the issue showed a late tail for G4. [Added in press: after the meeting Lubomir reproduced his timing plot, indeed G3 is the one with the late tail, consistent with our conclusion.] Also Tegan's plots show G4 and G4-NHL agree as far as timing goes. They also agree in terms of energy in Tegan's photon particle gun study (slides in the GlueX Doc).

Richard speculated that these late photons were from excited nuclear resonances decaying way after the particle gun fired. He asked if Tegan could look further s this using the parent particle information on the special branch.

Zisis suggested that Tegan check with Sean about other areas that could be studied.

G3/G4 Difference in FDC wire efficiency at the cell boundary

On Issue #181, Lubomir has done some Garfield studies to try to calculate efficiencies for the FDC. He is generating tracks at various positions in the cell and with various angles. He had two questions on how to proceed:

  1. What to do with tracks that hit two adjacent cells in a layer? Richard suggested that he treat each cell separately, each with its own DOCA.
  2. What drift time window should be applied to hits? Simon told us that mcsmear imposes a time cut at 1 μs.

Agreement of Simulation with Data

We briefly discussed the meta-topic of where, meeting-wise, we should discuss issues around agreement of the simulated data with real data. A lot of recent issues center around mcsmear and thus are not HDGeant4 topics per se. There was a general feeling that we could morph the mission statement for the meeting to include these topics as well. If only we had a mission statement...