[Halld-offline] HDGeant4 Meeting Minutes, April 9, 2019

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_April_9,_2019#Minutes> 
and below.

   -- Mark

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    HDGeant4 Meeting Minutes, April 9, 2019

Present:

  * *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 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_March_26,_2019#Minutes> 
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 
<https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=3964> 
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
    the calorimeters.
  * 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
    checked.

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 
<https://github.com/JeffersonLab/HDGeant4/issues/101>, "Differences 
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.

Retrieved from 
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  * This page was last modified on 9 April 2019, at 17:48.

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