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<p>Please find the minutes from last week's meeting <a
moz-do-not-send="true"
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_November_19,_2019#Minutes">here</a>
and below.</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">HDGeant4 Meeting, November 19, 2019, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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<div id="mw-content-text" dir="ltr" class="mw-content-ltr"
lang="en">
<p>Present:
</p>
<ul>
<li> <b> CMU: </b> Naomi Jarvis</li>
<li> <b> FSU: </b> Sean Dobbs</li>
<li> <b> JLab: </b> Alex Austregesilo, Mark Dalton,
Mark Ito (chair), Igal Jaegle, Keigo Mizutani, Simon
Taylor, Beni Zihlmann</li>
<li> <b> ODU: </b> Nilanga Wickramaarachchi</li>
<li> <b> UConn: </b> Richard Jones</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/PWXzm/">recording of
this meeting</a> on the BlueJeans site. Use your JLab
credentials to get access.
</p>
<h3><span class="mw-headline" id="Announcement">Announcement</span></h3>
<p>Mark announced a <a rel="nofollow" class="external
text"
href="https://mailman.jlab.org/pipermail/halld-offline/2019-November/003819.html">New
version set: version_4.11.0.xml</a>. This one
incorporates the nuclear ions recently added by Richard.
</p>
<p>Alex asked if the new ions definitions render old
reconstruction launch halld_recon version incompatible
with the latest halld_sim versions. Seems like they are.
We will have to patch those halld_recon versions before
they can be used with modern simulation.
</p>
<h3><span class="mw-headline"
id="Review_of_Minutes_from_the_November_5_Meeting">Review
of Minutes from the November 5 Meeting</span></h3>
<p>We went over <a
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_November_5,_2019#Minutes"
title="HDGeant4 Meeting, November 5, 2019">the minutes</a>.
</p>
<h4><span class="mw-headline"
id="Visualization_with_OpenGL">Visualization with
OpenGL</span></h4>
<p>Igal's problem was resolved by sitting down with
Richard and adding a missing command option in his
vis.mac.
</p>
<h4><span class="mw-headline"
id="Python_Interface_Problem">Python Interface Problem</span></h4>
<p>Igal, again working with Richard, got single-threaded
builds of both geant4 and hdgeant4, as suggested at the
last meeting, and had success using the Python
interface.
</p>
<h4><span class="mw-headline" id="Neutron_Simulation">Neutron
Simulation</span></h4>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/125">Issue
#125</a>. Richard looked into Igal's suggestion from
last time and found the "high precision" option in the
documentation. Enabling it would like solve the problem
for low energy neutrons (less than 20 MeV) but at an
unknown cost in execution time. We will give it a try.
There may be other less compute intensive solutions as
well.
</p>
<p>This problem does not occur in hadronic showers because
of the "neutron killer" in Geant4. Initial state
neutrons are not subject to getting killed.
</p>
<h4><span class="mw-headline"
id="Difference_in_Acceptance_between_G3_and_G4">Difference
in Acceptance between G3 and G4</span></h4>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/111">Issue
#111</a>. Colin Gleason responded to Mark's email. He
says that this is still a problem and he will try to
repeat the study with a modern version of the software.
He did report running into problem when trying with
halld_sim 4.9.1.
</p>
<h4><span class="mw-headline" id="Terminal_cleanup.3F">Terminal
cleanup?</span></h4>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/102">Issue
#102</a>. Mark pointed out that Richard has already
completed this request. Mark will mark it as closed.
</p>
<p>On a related note, Mark remarked that hdgeant4 is
printing out the random number seeds for each event. He
will look into removing -DVERBOSE_RANDOMS[?] from the
compiler switches for hdg4, as per Naomi and Richard.
</p>
<h3><span class="mw-headline"
id="Calorimeter_timing_mismatch_between_g3_and_g4">Calorimeter
timing mismatch between g3 and g4</span></h3>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/93">Issue
#93</a>, having to do with charged particle timing
measurements in our two calorimeters. Since the last
meeting Alex did a three-way comparison of timing among
G3, G4, and data. See the plots below.
</p>
<table>
<tbody>
<tr>
<td>
<div class="thumb tright">
<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Bcal_timing_aa.png"
class="image"><img alt=""
src="https://halldweb.jlab.org/wiki/images/thumb/5/5f/Bcal_timing_aa.png/300px-Bcal_timing_aa.png"
class="thumbimage" width="300"
height="218"></a>
<div class="thumbcaption">BCAL</div>
</div>
</div>
</td>
<td>
<div class="thumb tright">
<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Fcal_timing_aa.png"
class="image"><img alt=""
src="https://halldweb.jlab.org/wiki/images/thumb/e/e7/Fcal_timing_aa.png/300px-Fcal_timing_aa.png"
class="thumbimage" width="300"
height="222"></a>
<div class="thumbcaption">FCAL</div>
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</div>
</td>
</tr>
</tbody>
</table>
<p>We noted that the FCAL sample is unusual in that if the
FCAL is being used for timing, that means that there was
no TOF hit to use, which should not be the case most of
the time.
</p>
<p>There are significant tails being cut by the analysis
library, as can be seen on the plots. This might explain
differences in high-level efficiency for events with a
particular topography, especially if these timing cuts
are applied for multiple particles. The high-level
efficiency studies should be repeated with wider time
windows to see if the G3 vs. G4 comparison is affected.
</p>
<h3><span class="mw-headline"
id="Comparison_of_geant3.2Fgeant4_for_.CE.B3_p_.E2.86.92_K.2B.CE.A30">Comparison
of geant3/geant4 for γ p → K<sup>+</sup>Σ<sup>0</sup></span></h3>
<p>Nilanga showed <a rel="nofollow" class="external text"
href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=4270a">comprehensive
set of slides on acceptance</a> for this channel
comparing G3 with G4 and with data.
</p>
<p>For the t-channel he showed
</p>
<ul>
<li> the t-distribution for
<ul>
<li> thrown events</li>
<li> events accepted in the G3 simulation</li>
<li> events accepted in the G4 simulation</li>
<li> acceptance for G3 and G4</li>
<li> accepted real data events</li>
</ul>
</li>
<li> For single particles, he showed
<ul>
<li> 2-D plots of momentum vs. polar angle, for both
thrown and reconstructed, and for both G3 and G4.</li>
<li> 1-D plots of momentum and polar angle, G3 and
G4</li>
<li> 2-D plots of momentum vs. polar angle for data</li>
<li> all of these were shown for K<sup>+</sup>, π<sup>−</sup>,
p, and γ</li>
</ul>
</li>
</ul>
<p>Also all of these plots were shown for the u-channel as
well. So that is a lot of plots.
</p>
<p>Naomi (and others) noted that the following slide was
especially interesting:
</p>
<table>
<tbody>
<tr>
<td>
<div class="thumb tright">
<div class="thumbinner" style="width:302px;"><a
href="https://halldweb.jlab.org/wiki/index.php/File:Nilanga_features.png"
class="image"><img alt=""
src="https://halldweb.jlab.org/wiki/images/thumb/c/c6/Nilanga_features.png/300px-Nilanga_features.png"
class="thumbimage" width="300"
height="202"></a>
<div class="thumbcaption">G3 vs. G4 features
in Nilanga's analysis</div>
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</div>
</td>
</tr>
</tbody>
</table>
<p>She noted
</p>
<blockquote>
<p>The other pages showed generally fewer particles
(pi-, p, gamma) reconstructed through G3 than G4 for
the u-channel events - these have the backward
low-momentum K+ but the general lack of other
particles in a smoother way would be explained by this
sharp absence of K+. K+ was the only particle with a
dramatic dip. The data also show a dip in u-channel
yield vs -u which matches the G3 plot, but not G4, so
it looks like something is going awry with G4 somehow.
</p>
</blockquote>
<p>Richard will have a look at trying to reproduce these
odd features with a particle gun.
</p>
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