<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>
<p>Folks,</p>
<p>Please find the minutes <a moz-do-not-send="true"
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_March_9,_2021#Minutes">here</a>
and below.</p>
<p> -- Mark</p>
<p> __________________________________________</p>
<p>
</p>
<div id="globalWrapper">
<div id="column-content">
<div id="content" class="mw-body" role="main">
<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">HDGeant4 Meeting, March 9, 2021, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
<div id="bodyContent" class="mw-body-content">
<div id="mw-content-text" dir="ltr" class="mw-content-ltr"
lang="en">
<p>Present: Tegan Beattie, Mark Ito (chair), Richard
Jones, Zisis Papandreou, Churamani Paudel, Lubomir
Pentchev, Justin Stevens, Simon Taylor, Nilanga
Wickramaarachchi
</p>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/wKdTln_kEz3/">recording
of this meeting</a> on the BlueJeans site. Log into
the BlueJeans site 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,_February_23,_2021#Minutes"
title="HDGeant4 Meeting, February 23, 2021">minutes
from February 23rd</a>. Richard has <a rel="nofollow"
class="external text"
href="https://mailman.jlab.org/pipermail/halld-offline/2021-February/008475.html">already
made the proposed changes to the tagger-hit-to-energy
conversion</a>. Pull requests await merging in the
halld_recon and halld_sim repositories.
</p>
<h3><span class="mw-headline"
id="New_wiki_page:_Particle_Gun_Collection">New wiki
page: Particle Gun Collection</span></h3>
<p>Richard described an upcoming historical catalog of
single particle gun simulations. See <a
href="https://halldweb.jlab.org/wiki/index.php/Particle_Gun_Collection"
title="Particle Gun Collection">his new wiki page</a>
for the complete description.
</p>
<h3><span class="mw-headline" id="Issues_on_GitHub">Issues
on GitHub</span></h3>
<p>We went over <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues">the
issues</a>.
</p>
<h4><span class="mw-headline"
id="Hits_in_both_CALs_from_the_same_track">Hits in
both CALs from the same track</span></h4>
<p>Lubomir led us through a discussion of <a
rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/185">Issues
on GitHub</a>. Two ideas that came up:
</p>
<ul>
<li> There might be an effect where a charged particle's
trajectory is extrapolated beyond what is reasonable,
allowing it to hit the FCAL and create a spurious
match there.</li>
<li> Particles that clip the corner of the BCAL and send
parts of the shower into the FCAL could explain some
of the double matching. This behavior could be
different between G3 and G4.</li>
</ul>
<p>For all the details, see the Issue itself, linked
above.
</p>
<h4><span class="mw-headline"
id="Proton_timing_in_the_BCAL">Proton timing in the
BCAL</span></h4>
<p>Again, <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/179">Issue
#179</a> has mainly to do with late hits in the BCAL
from charged hadrons. Tegan presented results from a
study to determine the physical mechanism for the late
hits, as usual,comparing the effects among G4, G3/HADR1,
and G3/HADR4. It turns out identifying parent particles
for the particles creating late hits was not possible in
an unambiguous manner. He was able to plot the timing
distributions for the various physical interaction
mechanisms separately, again comparing the different
Geant engines. In fact, some of these interactions
happen quite late, tens of nanoseconds after the event.
</p>
<p>For all of the details see <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=4878">Tegan's
plots on the DocDB</a>. They are the ones with "MAR04"
in the name.
</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>Richard reported on the root cause of <a
rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/181">Issue
#181</a>. Interestingly, the G3 simulation agrees
better with the data because of the requirement that
only one cell in a layer is hit. This artificially
eliminates hits from tracks that spend a small amount of
time in a cell, but happily since those trajectory have
lower detection efficiency, their elimination mimics
what is seen in data. The G4 simulation has no such
mechanism for eliminating corner-clipping tracks and so
hits with long drift times are produced at a rate higher
than seen in the data.
</p>
<p>See the Issue, linked above, for a more detailed
explanation, with diagrams.
</p>
<p>We seemed to be forming a consensus that Richard should
allow multiple hits per layer, but implement an
efficiency function that reduced the number of large
DOCA hits.
</p>
<p>[Added in press: in the issue itself you will see
Richard's description of adding actual wires to the FDC
simulation geometry.]
</p>
</div>
<br>
</div>
</div>
</div>
</div>
</body>
</html>