[Halld-offline] HDGeant4 Meeting Minutes, April 9, 2019
marki at jlab.org
Tue Apr 9 17:51:48 EDT 2019
Please find the minutes here
HDGeant4 Meeting Minutes, April 9, 2019
* *CMU: * Naomi Jarvis
* *Glasgow: * Peter Pauli
* *JLab: * Alex Austregesilo, Thomas Britton, Mark Dalton, Stuart
Fegan, Mark Ito (chair), Simon Taylor, Beni Zihlmann
There is a recording of this meeting <https://bluejeans.com/s/5Ft48/> on
the BlueJeans site <https://jlab.bluejeans.com/>. Use your JLab
credentials to access it.
Review of minutes from the last meeting
We went over the minutes from the March 26th meeting
without significant comment.
Do-over on comparison studies
Simon is working on analysis of his particle gun simulations.
Geant3/4 comparisons for the K-, K+ and p particle gun
Peter led us though the set of summary slides
from his particle gun studies. He chose protons and charged kaons
because they are relevant to his analysis. Further he chose kinematic
regions for each that match his reaction. He created monitoring plots
for each species and had posted the complete set of plots for each as
part of his GlueX Note.
The summary alone runs to 72 slides and we went through them all in the
course of about an hour. The secretary does not have detailed notes on
each slide, but will record here some general remarks:
* Peter told us he chose plots that seemed interesting, either because
they showed good agreement between GEANT and Geant4 or, more likely,
because there were puzzling differences.
* As a general guide, if two plots are shown on the same pad, the blue
is GEANT and the red is Geant4. If there are two separate pads, then
the top is GEANT, the bottom is Geant4.
* He sees a charged particle reconstruction efficiency for Geant4 that
is about 10% lower than that for GEANT. Alex noted that this is
similar to what he is seeing when he studies ρ^0 events.
* Peter mentioned that the differences he picked out are mostly of two
broad classes: (1) energy or (2) timing, in each case as measured by
* We noted that since the z-position of charged particles is not well
measured for single particles, some the the timing distributions may
be hard to understand. Still they should have similar features in
GEANT vs. Geant4.
* The versions of the code he used came before Richard's most recent
pull request <https://github.com/JeffersonLab/HDGeant4/pull/100>,
symmetrizing the treatment of timing between the FCAL and BCAL. Some
of the differences may have lessened in the new code; this should be
Please consult the recording if interested in a plot-by-plot discussion.
Issue on GitHub: missing thrown events
Thomas called our attention to Issue #101 on GitHub
between G3 and G4 in eta.pi," submitted by Carlos Salgado. Carlos sees a
completely different thrown momentum distribution for protons when using
GEANT vs. Geant4 even though the generated events are identical in the
two cases. Indeed they come from the same HDDM file.
* This page was last modified on 9 April 2019, at 17:48.
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