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<p>Colleagues,</p>
<p>Please find the minutes <a moz-do-not-send="true"
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_April_6,_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, April 6, 2021, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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lang="en">
<p>Present: Tegan Beattie, Mark Ito (chair), Richard
Jones, Zisis Papandreou, Lubomir Pentchev, Simon Taylor,
Beni Zihlmann
</p>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/N2e10KAyLf3/">recording
of this meeting</a> on the BlueJeans site. Log into
the <a rel="nofollow" class="external text"
href="https://jlab.bluejeans.com">BlueJeans site</a>
first to gain access (use your JLab credentials).
</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,_March_23,_2021#Minutes"
title="HDGeant4 Meeting, March 23, 2021">minutes from
the meeting on March 23rd</a>. Richard suggested we
close <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/181">Issue
#181</a>, "G3/G4 Difference in FDC wire efficiency at
the cell boundary" as an HDGeant4 issue and re-open the
remaining work to get data/MC agreement as a halld_sim
issue, specifically one with mcsmear, now that our
various simulation engines agree with one another.
</p>
<h3><span class="mw-headline" id="Issues_on_GitHub">Issues
on GitHub</span></h3>
<h4><span class="mw-headline"
id="Proton_timing_in_the_BCAL">Proton timing in the
BCAL</span></h4>
<p>On <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/179">Issue
#179</a> Tegan presented further work using the <a
rel="nofollow" class="external text"
href="https://mailman.jlab.org/pipermail/halld-offline/2021-March/008496.html">test
branch of HDGeant4</a> Richard provided that supplies
parent particle information. Armed with this new tool he
showed <a rel="nofollow" class="external text"
href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=4878">some
new plots (APR02_ProtonComparison.pdf)</a> with a
proton particle gun aimed at the BCAL. Each slides has
plots for G4, G4-NHL, G3-HADR1, and G3-HADR4.
</p>
<ul>
<li> slide 12: Photon production mechanism vs. time.</li>
<li> slide 20: Photon production mechanism vs. parent
particle ID</li>
<li> slide 10: Photon, positron, electron, and pi+
production times</li>
<li> slide 8: Photon, positron, electron, and pi+ energy
spectra</li>
</ul>
<p>The overall conclusion from the Tegan's study is that
G3-HADR1 is the one model that shows a long, late timing
tail (slide 3), even though the plot from Lubomir linked
at the beginning of the issue showed a late tail for G4.
[Added in press: after the meeting Lubomir reproduced
his timing plot, indeed G3 is the one with the late
tail, consistent with our conclusion.] Also Tegan's
plots show G4 and G4-NHL agree as far as timing goes.
They also agree in terms of energy in Tegan's photon
particle gun study (slides in the GlueX Doc).
</p>
<p>Richard speculated that these late photons were from
excited nuclear resonances decaying way after the
particle gun fired. He asked if Tegan could look further
s this using the parent particle information on the
special branch.
</p>
<p>Zisis suggested that Tegan check with Sean about other
areas that could be studied.
</p>
<h4><span class="mw-headline"
id="G3.2FG4_Difference_in_FDC_wire_efficiency_at_the_cell_boundary">G3/G4
Difference in FDC wire efficiency at the cell boundary</span></h4>
<p>On <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/181">Issue
#181</a>, Lubomir has done some Garfield studies to
try to calculate efficiencies for the FDC. He is
generating tracks at various positions in the cell and
with various angles. He had two questions on how to
proceed:
</p>
<ol>
<li> What to do with tracks that hit two adjacent cells
in a layer? Richard suggested that he treat each cell
separately, each with its own DOCA.</li>
<li> What drift time window should be applied to hits?
Simon told us that mcsmear imposes a time cut at 1 μs.</li>
</ol>
<h3><span class="mw-headline"
id="Agreement_of_Simulation_with_Data">Agreement of
Simulation with Data</span></h3>
<p>We briefly discussed the meta-topic of where,
meeting-wise, we should discuss issues around agreement
of the simulated data with real data. A lot of recent
issues center around mcsmear and thus are not HDGeant4
topics per se. There was a general feeling that we could
morph the mission statement for the meeting to include
these topics as well. If only we had a mission
statement...
</p>
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