HDGeant4 Meeting, May 19, 2020

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HDGeant4 Meeting
Tuesday, May 19, 2020
3:30 pm EDT
BlueJeans: 968 592 007


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


Present: Alex Austregesilo, Sean Dobbs, Colin Gleason, Mark Ito (chair), Naomi Jarvis, Richard Jones, Churamani Paudel, Joerg Reinhold, Justin Stevens, Simon Taylor, Nilanga Wickramaarachchi, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site. Use your JLab credentials to get access.

Review of minutes from the last Meeting

We went over [[HDGeant4 Meeting, May 5, 2020#Minutes|the minutes from May 5].

  • Nilanga will close Issue #137, "K particle gun request to resolve G3/G4 difference near p 0.5 GeV/c and theta 120 degrees" and re-open it as a halld_recon issue. There is concern about loss of tracking efficiency in the backward region of the CDC.

Issues on GitHub

We reviewed some of the issues.

Difference in Acceptance between G3 and G4 #111

We noted the one-year anniversary of this issue. We started with comments entered yesterday (Monday). Colin showed plots where the acceptance of charged pions can vary as much between the two hadronic codes in Geant3 as from that in Geant4. Protons look similar among the three.

Richard commented that response of the calorimeters could depend on the details of very low energy processes, including those of alphas and neutrons and for the BCAL, that response depend a lot on whether the interactions take place in the lead or in the scintillator. Recall that the simulated BCAL is composed of a fictional, average lead-scintillator compound. Saturation in the scintillator may be in play as well. For the Cerenkov response of the FCAL there are similar uncertainties for the response to low energy processes.

Sean suggested removing the requirement of matching of charged particles to one of the outer detectors as a cross-check on the acceptance.

Colin also showed timing distribution of the various particle species in his reaction. Differences in the photon timing resolution function for the BCAL are seen between data and all Monte Carlo samples, a difference that was not expected and needs to be explored further. He also showed comparisons for timing from the time-of-flight. Here the pi show a wide distribution for data than for Monte Carlo.

BCAL Timing

Sean showed some slides from Mark Dalton, shown at the May 16, 2019 Collaboration Meeting (one year ago), showing comparisons between data and simulations of timing resolution for both neutral showers and charged particles. He also showed offsets as a function of energy, z, and run number for both neutral showers and charged showers. He presented them as outstanding puzzles that this group might want to address.

Pull Requests on GitHub

We looked at pull requests. Richard has introduced a new card to allow users to use the CCDB to specify the vertex position in the transverse plane as well as the x and y spread of the beam. The information comes from the measured position of two track vertices found in the tracking, a facility developed by Simon.

Justin pointed out that this feature should be accessible via MCwrapper.