[Halld-offline] HDGeant4 Meeting Minutes, August 11, 2020

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_August_11,_2020#Minutes> 
and below.

   -- Mark


    HDGeant4 Meeting, August 11, 2020, Minutes

Present: Alex Austregesilo, Sean Dobbs, Mark Ito (chair), Igal Jaegle, 
Naomi Jarvis, Richard Jones, Mahmoud Kamel, Churamani Paudel, Simon 
Taylor, Nilanga Wickramaarachchi, Beni Zihlmann

There is a recording of this meeting 
<https://bluejeans.com/s/ziPr0UPh_Ww/> on the BlueJeans site. Use your 
JLab credentials to get access.


      Review of minutes from the last meeting

We went over the minutes from July 14 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_July_14,_2020#Minutes>, 
a month ago now. Richard has made the judgment that the problem with 
particle propagation not being able to find the normal to a surface, 
reported as a warning, occurs rarely enough that it should not cause a 
problem for us. This we can live with.


      Issues on GitHub

We reviewed the issues <https://github.com/JeffersonLab/HDGeant4/issues>.

  * hdgeant4 hanging at first event
    <https://github.com/JeffersonLab/HDGeant4/issues/169>. This problem
    was introduced in the effort to get reproducible results from all
    hdgeant4 output events based on the two input random number seeds.
    The application of mutex locks introduced to use certain ROOT
    functionality involving the ROOT random number generator had a bug.
    This is now fixed. Igal will close the issue.
  * G4 exceptions for certain run numbers
    <https://github.com/JeffersonLab/HDGeant4/issues/167>. We will
    follow up with Elton on this issue. I may be due to trying to
    reconstruct TOF-II data with TOF-I-only-compatible software.
  * Difference in Acceptance between G3 and G4
    <https://github.com/JeffersonLab/HDGeant4/issues/111>. Colin
    Gleason's last post on this issue showed a large difference in
    overall event acceptance if simulated with Richard's "no heavy
    light" branch. The acceptance goes down by a factor of several. We
    will likely need further guidance from Colin on what particles in
    the event are creating the difference.


      Holes in γγ→η Invariant Mass

Mahmoud showed an anomaly in the two-photon invariant mass distribution 
near the η. There are dips on either side of the η mass. See his figure 
below (lower left plot). The dips come from two regions of beam photon 
energy which are near the corresponding boundaries between the tagger 
microscope and hodoscope. The regions show as dark blue in the lower 
right plot. There may some issue with some kind of subtraction from the 
data since the holes have negative entries in the histogram. Mahmoud 
will enter this as an issue.

Hdgeant 8 11 2020.png 
<https://halldweb.jlab.org/wiki/index.php/File:Hdgeant_8_11_2020.png>

Added in press: this is now Issue #173 
<https://github.com/JeffersonLab/HDGeant4/issues/173>.

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  * This page was last modified on 11 August 2020, at 17:56.

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