<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<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_12,_2019#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">Minutes, HDGeant4 Meeting, March 12, 2019</span></h2>
<div id="bodyContent" class="mw-body-content">
<div id="mw-content-text" dir="ltr" class="mw-content-ltr"
lang="en">
<p>Present:
</p>
<ul>
<li> <b> Glasgow: </b> Peter Pauli</li>
<li> <b> JLab: </b> Shankar Adhikari, Alex
Austregesilo, Thomas Britton, Stuart Fegan, Mark Ito
(chair), Simon Taylor, Beni Zihlmann</li>
<li> <b> UConn: </b> Richard Jones</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/1aas1/">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 reviewed <a
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_February_26,_2019#Minutes"
title="HDGeant4 Meeting, February 26, 2019">the
minutes from February 26</a>. Simon continues to work
on single-particle gun comparisons of HDG3 vs. HDG4.
</p>
<h3><span class="mw-headline"
id="Discussion.2Fproposal_for_making_transition_to_G4">Discussion/proposal_for_making_transition_to_G4</span></h3>
<p>Mark led us through the <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Software_Meeting,_March_5,_2019#Discussion.2Fproposal_for_making_transition_to_G4"
title="GlueX Software Meeting, March 5, 2019">discussion
from the last Software Meeting</a> on a policy for
making the transition to HDG4. He concludes that there
was no consensus on what the policy should be. Since
studies and comparisons are going forward in any case,
he proposed, and the group agreed, that we drop the idea
of a formal policy. As a corollary, we are dropping the
idea of a document to support collaboration-wide
adoption of HDG4; the recommendation that we do so has
essentially been rejected, at least for now.
</p>
<h3><span class="mw-headline"
id="G3.2FG4_comparison_for_.CF.81.28770.29_cross_section:_after_ST_fix.2C_without_trigger_emulation">G3/G4
comparison for ρ(770) cross section: after ST fix,
without trigger emulation</span></h3>
<p>Alex repeated his study from two weeks ago with a fix
to the start counter geometry and with no trigger
emulation as suggested last time. His presentation
starts at 12:50 in the recording.
</p>
<p>He first showed the <a rel="nofollow" class="external
text"
href="https://halldweb.jlab.org/wiki/images/9/9d/Accpentance_g3_g4_notrigger.pdf">overall
acceptance as a function of energy</a>. Removing the
trigger emulation had almost no effect. The disagreement
at low energy remains.
</p>
<p>Next he showed a selection from the <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/talks/2019/Independent_rho_G3_G4_noTrigger.pdf">large
number of comparison plots he produced</a>. He
highlighted the following areas (with page numbers):
</p>
<ol>
<li> FDC Cathode (32.54)</li>
<li> B/FCal Shower Energy (76/77, 308/311)</li>
<li> Timing of charged tracks in FCal/BCal (866/873)</li>
<li> Tracking below 12 degrees (1041)</li>
</ol>
<p>In general things look more similar than they did in
the previous version of the the study.
</p>
<ul>
<li> The number of FDC hits on tracks shows a
significant difference, 10-20% more hits in the HDG4
simulation. Richard thought this might be due to
difference in energy deposition physics in G3 vs. G4.</li>
<li> The time of charged particles measured in the BCAL
vs the real time has a high-side tail much larger for
HDG3 than for HDG4. Since these may be hadronic
showers, Richard stated that neither is to be trusted.</li>
<li> Alex showed a <a rel="nofollow" class="external
text"
href="https://halldweb.jlab.org/wiki/images/3/35/G3_G4_combocontruction.png">plot
showing were events are cut in the analysis chain</a>.
In particular, there is cut that requires all charged
particles to agree on the RF bunch that caused the
event. The plot shows a much larger number of events
eliminated by the timing agreement cut for HDG3 than
for HDG4 about a factor of two. This may be related to
the BCAL timing effecting the proton time.
<ul>
<li> Richard will look at the these BCAL timing
distributions in real data. Perhaps neither
simulation does a good job and we should smear
this quantity with distributions derived from real
data.</li>
</ul>
</li>
</ul>
<h3><span class="mw-headline"
id="FCAL:_comparing_G3_and_G4">FCAL: comparing G3 and
G4</span></h3>
<p>Richard gave <a rel="nofollow" class="external text"
href="https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=3852">an
update on the energy response of FCAL</a>, comparing
HDG3 and HDG4.
</p>
<ul>
<li> The work had benefited from interactions with the
Calorimeter Group.</li>
<li> He compares shower energy, after full simulation,
smearing, reconstruction, and non-linearity
correction.</li>
<li> The comparison is done in slices of polar angle.</li>
<li> Agreement between HDG3 and HDG4 is very good.</li>
<li> He sees a significant remaining non-linearity, both
at low energy (below 1 GeV) and at high energy (above
4 GeV). The character of the non-linearity for HDG3 is
the same as that for HDG4.</li>
</ul>
<p>He did not show the corresponding BCAL study but told
us that the agreement is goo there as well. He now plans
to start looking at timing in the calorimeters.
</p>
<h3><span class="mw-headline"
id="Review_of_Issues_and_Pull_Requests">Review of
Issues and Pull Requests</span></h3>
<p>Jon Zarling reported an issue, <a rel="nofollow"
class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/94">Photon
Gun Sample Changes Behavior after ~500,000 events? #94</a>
where photons from the gun do not escape the target deep
into the HDGeant4 run. Naomi Jarvis was able to
reproduce it. The problem was real, Richard got to the
bottom of it, it has been reported to the Geant4
Collaboration, and a fix implemented in HDGeant4. For
details of the bug, see Issue #94 on GitHub.
</p>
</div>
<div class="printfooter">
Retrieved from "<a dir="ltr"
href="https://halldweb.jlab.org/wiki/index.php?title=HDGeant4_Meeting,_March_12,_2019&oldid=91808">https://halldweb.jlab.org/wiki/index.php?title=HDGeant4_Meeting,_March_12,_2019&oldid=91808</a>"</div>
</div>
</div>
</div>
<div id="footer" role="contentinfo">
<ul id="f-list">
<li id="lastmod"> This page was last modified on 17 March
2019, at 13:08.</li>
</ul>
</div>
</div>
</body>
</html>