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<p>Folks,</p>
<p>Please find the minutes <a moz-do-not-send="true"
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_January_26,_2021#Minutes">here</a>
and below.</p>
<p> -- Mark</p>
<p> ____________________________________________</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">HDGeant4 Meeting, January 26, 2021, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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lang="en">
<p>Present: Alex Austregesilo, Tegan Beattie, Sean Dobbs,
Mark Ito (chair), Igal Jaegle, Richard Jones, Zisis
Papandreou, Dmitry Romanov, Simon Taylor, Nilanga
Wickramaarachchi, Jon Zarling, Beni Zihlmann
</p>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/0dT7O1tS3dq/">recording
of this meeting</a> on the BlueJeans site. Use your
JLab credentials to get access.
</p>
<h3><span class="mw-headline" id="Announcements">Announcements</span></h3>
<p>Mark announced a brand <a rel="nofollow"
class="external text"
href="https://mailman.jlab.org/pipermail/halld-offline/2021-January/008443.html">new
version set, 4.35.0</a>.
</p>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_last_meeting">Review of
minutes from the last meeting</span></h3>
<p>We went over the <a
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_December_15,_2020#Minutes"
title="HDGeant4 Meeting, December 15, 2020">minutes
from December 15</a>.
</p>
<ul>
<li> Mark reported that he can no longer reproduce the
"make clean" error. Richard reported that there is no
explicit "clean" target in the HDGeant4 makefile.
Instead it depends on the default target.</li>
<li> Mark built the no-heavy-light (NHL) branch of
HDGeant4 at JLab.</li>
</ul>
<h3><span class="mw-headline"
id="G4_Standard.2FNo_Heavy_Light_comparison">G4
Standard/No Heavy Light comparison</span></h3>
<p>Tegan showed a <a rel="nofollow" class="external text"
href="https://halldweb.jlab.org/DocDB/0048/004878/001/c1.pdf">plot of
proton BCAL timing</a> from HDGeant4 comparing the NHL
branch with a standard build. The reaction simulated was
γp→ηp. Very little difference is seen.
</p>
<ul>
<li> Richard suggested checking that the deposited
energy is different between the two versions, as a
cross-check that the right branch is being tested.</li>
<li> Sean mentioned that Colin was looking at pions and
that momentum dependence may be important.</li>
<li> Zisis asked for suggestions for studies for Tegan
to do in pursuing <a rel="nofollow" class="external
text"
href="https://github.com/JeffersonLab/HDGeant4/issues/179">Issue
#179</a>. Richard suggested looking along the track
and study how energy is deposited along the path. Sean
endorsed this approach, especially for secondaries, as
a function of particle type.</li>
<li> Sean noted that <a rel="nofollow" class="external
text"
href="https://github.com/JeffersonLab/HDGeant4/files/5639678/Nov20_g3_vs_g4_dtlog.pdf">his
PDF linked to the issue</a> shows the timing tail.</li>
<li> Sean also noted that Hao Li has a large sample of
protons in his studies and a comparison of that sample
with Monte Carlo might shed some light on the issue.</li>
</ul>
<h3><span class="mw-headline"
id="No_TAGH_Hits_in_Simulation">No TAGH Hits in
Simulation</span></h3>
<p>Drew Smith reported a lack of tagger hodoscope hits in
the sampling region in HDGeant4. Richard explained that
this is due to a bug where the scheme for converting
tagger counter ID to photon energy is inconsistent with
the way the tagger energy scale is reported from the
CCDB. Drew and Igal will submit an issue and Richard
will come up with a fix.
</p>
<h3><span class="mw-headline"
id="G3.2FG4_comparison:_FDC_Wire_Efficiency">G3/G4
comparison: FDC Wire Efficiency</span></h3>
<p>Alex has noticed a difference in <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/talks/2021/FDC_Efficiency/g3_g4_comparison.pdf">FDC
wire efficiency</a> when calculated with GEANT 3 vs.
Geant4. He analyzed his ρ photoproduction sample. We
mainly discussed the drop of efficiency at large drift
distance seen in GEANT 3, but not in Geant4. Although
one expect such a drop due distortions of the field
lines near the edges of the cell, those effects are in
neither version of the simulation. Alex will submit a
GitHub issue on this.
</p>
<h3><span class="mw-headline"
id="Problems_at_Low-t_in_genBH_Generator">Problems at
Low-t in genBH Generator</span></h3>
<p>Richard announced a GitHub issue-to-appear soon on the
kinematic distributions from the genBH generator.
</p>
<p>Mark mentioned that he has started to look at building
Diracxx as part of our standard software stack. genBH
requires this package.
</p>
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