[Halld-offline] HDGeant4 Meeting Minutes, May 19, 2020

[Mark Ito]

Folks,

Please find the minutes from last week's HDGeant4 Meeting here 
<https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_May_19,_2020#Minutes> 
and below.

   -- Mark


    HDGeant4 Meeting, May 19, 2020,Minutes

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 <https://bluejeans.com/s/TByqC/> 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
    <https://github.com/JeffersonLab/HDGeant4/issues/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 
<https://github.com/JeffersonLab/HDGeant4/issues>.


        Difference in Acceptance between G3 and G4 #111

We noted the one-year anniversary of this issue 
<https://github.com/JeffersonLab/HDGeant4/issues/111>. 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 
<https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=4053>, 
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 
<https://github.com/JeffersonLab/HDGeant4/pulls>. Richard has introduced 
a new card <https://github.com/JeffersonLab/HDGeant4/pull/153> 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.

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  * This page was last modified on 25 May 2020, at 18:20.

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