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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,_September_11,_2018#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">Minutes, HDGeant4 Meeting, September 11, 2018</span></h2>
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lang="en">
<p>Present:
</p>
<ul>
<li> <b> FSU: </b> Sean Dobbs</li>
<li> <b> JLab: </b> Thomas Britton, Mark Ito (chair),
Simon Taylor</li>
<li> <b> W&M: </b> Justin Stevens</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/iMoJk/">recording of
this meeting</a> on the BlueJeans site. Use your JLab
credentials.
</p>
<h3><span class="mw-headline"
id="Review_of_minutes_from_last_time">Review of
minutes from last time</span></h3>
<p>We reviewed <a
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_August_28,_2018#Minutes"
title="HDGeant4 Meeting, August 28, 2018">the minutes
from August 28</a>.
</p>
<ul>
<li> The change to make the time-to-distance relation
used in HDG3 match that of data (read it from the
CCDB) is in the latest tagged version of halld_sim
(3.4.0).</li>
<li> Sean reported that the 5 MeV shift in the 2γ mass
he reported last time is not limited to just the BCAL
or just the FCAL. Both contribute.</li>
</ul>
<h3><span class="mw-headline" id="Issues_on_GitHub">Issues
on GitHub</span></h3>
<p>We reviewed the extant <a rel="nofollow"
class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues">issues
on the GitHub site for HDGeant4</a>. Richard Jones
reported (via email) that he is working on the <a
rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/65">DIRC
time propagation anomaly</a> now.
</p>
<h3><span class="mw-headline"
id="New_Comparison:_4_GeV.2C_4_Degree_Protons">New
Comparison: 4 GeV, 4 Degree Protons</span></h3>
<p>Thomas presented plots from a <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=3740">new
comparison of 4 GeV, 4 degree protons</a> between HDG3
and HDG4. The comparison was done with all physics
processes (multiple scattering, energy loss, delta rays,
etc.) turned off.
</p>
<ul>
<li> The good agreement after fixes from Richard for 4
GeV protons at 15 degrees, seen after the last round
of fixes, stays good in this comparison.</li>
<li> The disagreement at 4 degrees persists. It is seen
in the following plots:
<ul>
<li> Tracking FOM, wire-based</li>
<li> Tracking FOM</li>
</ul>
</li>
<li> Thomas will work on getting more detailed plots
looking at timing distributions.</li>
<li> Events have not been scanned, as was done in the
previous round of corrections.</li>
<li> HDG3 and HDG4 get their geometry in different ways,
with the HDG3 geometry written into auto-generated
Fortran code and HDG4 getting it dynamically at run
time. We need to check that both are using the same
geometry for this comparison. That could explain the
difference between 4 and 15 degrees (or not).</li>
<li> Thomas will create a new GitHub issue based on this
study. [Added in press: see <a rel="nofollow"
class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/66">Issue
#66</a></li>
</ul>
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<pre class="moz-signature" cols="72">--
Mark Ito, <a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295
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