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Folks,<br>
<br>
Find the minutes below and at
<a class="moz-txt-link-freetext" href="https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_August_13,_2015#Minutes">https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_August_13,_2015#Minutes</a>
.<br>
<br>
-- Mark<br>
_____________________________________________________<br>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX Start Counter Meeting, August 13, 2015</span>,
Minutes</h2>
<div id="bodyContent" class="mw-body-content"><span
class="mw-headline" id="Minutes"></span>
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lang="en">
<p>Present:
</p>
<ul>
<li> <b>FIU</b>: Werner Boeglin, Mahmoud Kamel</li>
<li> <b>JLab</b>: Mark Ito (chair), Eric Pooser, Simon
Taylor</li>
</ul>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_August_3_meeting">Review
of minutes from the August 3 meeting</span></h3>
<p>We went over the <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_August_3,_2015#Minutes"
title="GlueX Start Counter Meeting, August 3, 2015">minutes</a>.
</p>
<ul>
<li> Eric has started on the GlueX Note describing the
calibration procedure.</li>
<li> For the time propagation correction he has decided
to use the measured delays[?] rather than a set
velocities with a different velocity for each region.</li>
<li> Eric updated the PID library to use the final
versions of the calibrations. The CCDB has been
updated as well.</li>
<li> The resulting time resolution is 60 ps below design
for all 30 paddles.</li>
<li> Eric pointed out that a years has gone by since
construction and there is no visible deterioration of
counter performance. Recall that in the past
degradation was apparent after a few months.</li>
</ul>
<h3><span class="mw-headline"
id="Start_counter_efficiency_calculations">Start
counter efficiency calculations</span></h3>
<p>Mahmoud presented slides describing how he determines
efficiencies and how the method has improved from
previous attempts. See <a rel="nofollow"
class="external text"
href="https://halldweb.jlab.org/talks/2015/ST_efficiency.pdf">his
slides</a> for details.
</p>
<p>Simon pointed out that, unless explicitly turned off,
there are a lot of tracks that get their t<sub>0</sub>
from the start counter. For these tracks, the existence
of start counter hit is therefore a given and the
efficiency might be artificially high. Mahmoud will
check whether this association between tracking and the
start counter was on or off (off: USE_SC_TIME=0).
</p>
<h3><span class="mw-headline" id="Calibration">Calibration</span></h3>
<p>Eric gave us an update on the calibration effort, in
particular the attenuation correction. For details see <a
rel="nofollow" class="external text"
href="https://halldweb.jlab.org/talks/2015/ST_Calibration_Update_Aug_13_2015.pdf">his
slides</a>.
</p>
<p>For work with the data he incorporated the path length
correction and is now calculating dE/dx (literally). The
distributions tighten up considerably. He has success
fitting the distributions to Vavilov distributions. The
problem with a lack of statistics at the upstream end
remains however. He settled on using the attenuation
values measured on the bench at FIU for the corrections.
</p>
<p>With the updates to the PID library to apply all of the
calibrations, Sean Dobbs asked about the plan for
installing calibration constants in the MC variation.
Eric has started looking at how the hits are created in
HDGeant. The idea is to apply constants that reverse the
process applied in event generation.
</p>
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