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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,_February_26,_2019#Minutes">here</a>
and below.</p>
<p> -- Mark</p>
<p>______________________________</p>
<p>
</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">Minutes, HDGeant4 Meeting, February 26, 2019</span></h2>
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lang="en">
<p>Present:
</p>
<ul>
<li> <b> CMU: </b> Naomi Jarvis</li>
<li> <b> JLab: </b> Alex Austregesilo, Thomas Britton,
Sean Dobbs, Stuart Fegan, Mark Ito (chair), Dmitry
Romanov, Simon Taylor, Beni Zihlmann</li>
<li> <b> UConn: </b> Richard Jones</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/fai_B/">recording of the
meeting on the BlueJeans site</a>. Use your JLab
credentials to access it.
</p>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_last_HDGeant4">Review
of minutes from the last HDGeant4</span></h3>
<p>We went over the <a
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_February_12,_2019#Minutes"
title="HDGeant4 Meeting, February 12, 2019">minutes of
the February 12 meeting</a>. Mark reported that there
is still no version set using the HDDS 3.14, the release
with pre-DIRC geometry baked in.
</p>
<h3><span class="mw-headline"
id="Do-over_on_comparison_studies">Do-over on
comparison studies</span></h3>
<p>Simon is working on a set of studies using the particle
gun, with all the physics of particle interaction with
matter turned on. He will report on it at a future
meeting.
</p>
<h3><span class="mw-headline"
id="Peter.27s_comparative_study_of_HDG3_vs._HDG4">Peter's
comparative study of HDG3 vs. HDG4</span></h3>
<p>Thomas led us through <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=3932">Peter
Pauli's slides</a> on a comparative study of pKK in
both Monte Carlo and data. Several slides showed
comparisons of histograms from four points of view:
</p>
<ol>
<li> as generated</li>
<li> as reconstructed after simulation with hdgeant</li>
<li> as reconstructed after simulation with hdgeant4</li>
<li> real data</li>
</ol>
<p>In many cases the hdgeant4 results looks a lot more
like data. Note that it is unlikely that the generated
distributions are the same as occur in the real world
(as Matt pointed out at the collaboration meeting), but
often the better agreement of data with hdgeant4 is due
to a lack of sharp features seen in the hdgeant
simulation and not in any of the other distributions.
Also the fits to SDME's look a lot better when using
hdgeant4 than with use of hdgeant. Peter concluded that
he needs to use hdgeant4 for his work.</p>
<h3><span class="mw-headline"
id="G3.2FG4_Comparison_for_.CF.81.28770.29_cross_section">G3/G4
Comparison for ρ(770) cross section</span></h3>
<p>Alex showed his recent comparative analysis of the
low-energy ρ data.
</p>
<p>First he showed a <a rel="nofollow" class="external
text"
href="https://halldweb.jlab.org/wiki/images/2/2b/G3_G4_comparison_1M.pdf">plot
comparing acceptance as a function of energy</a>. He
gets differences between G3 and G4 at lower beam photon
energy in constrast to results from Peter and Simon.
</p>
<p>He then showed highlights from <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/talks/2019/Independent_rho_G3_G4.pdf">comparisons
of monitoring histograms</a>, with the results of G3
and G4 overlayed on a single histogram. He used a macro
from Sean to do this. There are 1,277 such plots in
total. Here are the items he bookmarked:
</p>
<ul>
<li> FDC Cathode (32, 54)</li>
<li> StartCounter (290, 412++)</li>
<li> BCal (77, 252, 316)</li>
<li> FCal (287, 373)</li>
<li> Protons (526++, 976)</li>
<li> Pions (1028++)</li>
<li> Beam Photons (639)</li>
<li> Vertex time (113), Track timing (872++)</li>
</ul>
<p>There was some question about whether the HDG3 results
used the pre-DIRC geometry. Alex and Thomas will check
on this a re-run the simulation if necessary. Two
features stood out:
</p>
<ol>
<li> The start counter is missing its complement of
recoil protons at 60 degrees in polar angle. Alex will
submit an issue; Richard will investigate.</li>
<li> The effect of the trigger for low-energy beam
photons, seen in HDG3 is absent in HDG4. This could be
due to differences in the way charged hadrons are
treated in the FCAL. Differences in FCAL energy are
seen in the relevant plots which go in the right
direction (more energy for HDG4). More investigation
is needed.</li>
</ol>
<h3><span class="mw-headline" id="Written_Report">Written
Report</span></h3>
<p>Mark proposed <a rel="nofollow" class="external text"
href="https://docs.google.com/document/d/1ADvMWvdy63VePFmTOUc67zFaQGbMNfezn3MimD-biSw/edit?usp=sharing">an
outline for a written report</a> from this committee
describing the work we have done and recording our
recommendations. There were no strenuous objections to
going in the direction indicated.
</p>
<h3><span class="mw-headline" id="Issues_on_GitHub">Issues
on GitHub</span></h3>
<p>We looked at <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/89">Issue
#89: Hit Energy Agreement</a>, submitted earlier in
the day by Rebecca Barsotti. Richard summarized his
explanation of why differences in shower energy are not
surprising when comparing HDG3 and HDG4.
</p>
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