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Folks,<br>
<br>
Please find the minutes below and at <a class="moz-txt-link-freetext" href="https://goo.gl/CFkFcM">https://goo.gl/CFkFcM</a> .<br>
<br>
-- Mark<br>
___________________________<br>
<br>
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<h1 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX TOF Meeting, May 31, 2016, </span><span
class="mw-headline" id="Minutes">Minutes</span></h1>
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lang="en">
<p>Present:
</p>
<ul>
<li> <b>FSU</b>: Brad Cannon, Sasha Ostrovidov</li>
<li> <b>JLab</b>: Mark Ito (chair), Simon Taylor, Beni
Zihlmann</li>
</ul>
<h3><span class="mw-headline" id="Calibration">Calibration</span></h3>
<p>Beni gave us an update.
</p>
<p>He showed a plot of the difference in x as measured by
tracks and as measured by the TOF (simply by noting
which paddle was hit). The distribution is shown for
each paddle in the plane.
</p>
<p><a
href="https://halldweb.jlab.org/wiki/index.php/File:Tof_trkmatching.gif"
class="image"><img alt="Tof trkmatching.gif"
src="cid:part1.04050103.09030308@jlab.org"
srcset="/wiki/images/thumb/b/bf/Tof_trkmatching.gif/1050px-Tof_trkmatching.gif
1.5x, /wiki/images/b/bf/Tof_trkmatching.gif 2x"
height="453" width="700"></a>
</p>
<p>In the TOF measurement, it is assumed that the paddles
are 6 cm wide with no gaps. The slope seen in the plot
is due to the known gaps between counters (wrapping,
non-planar edges). A similar plot is shown for the
difference in y. From this method Beni measures a gap of
about 0.9 mm between the paddles. Simon is adding these
gaps to the geometry. In the reconstruction, this will
improve the matching to charged tracks.
</p>
<p>The timing calibration is done for all spring 2016
data.
</p>
<p>The plane with horizontal paddles is upstream in the
experiment but downstream in the current geometry. Simon
is fixing that by swapping the plane identifier: plane 0
becomes plane 1 and vice-versa.
</p>
<p>Sasha and Beni have both noticed a trend where the
matching has a lower efficiency near the beam line than
in the periphery. The track matching efficiency is less
than 95% in the central region.
</p>
<p>Beni sees a issue with the difference between ADC and
TDC timing in the central region.
</p>
<p><a
href="https://halldweb.jlab.org/wiki/index.php/File:T_offset_c17.gif"
class="image"><img alt="T offset c17.gif"
src="cid:part3.03080109.05070402@jlab.org"
srcset="/wiki/images/thumb/6/63/T_offset_c17.gif/450px-T_offset_c17.gif
1.5x, /wiki/images/6/63/T_offset_c17.gif 2x"
height="180" width="300"></a> <a
href="https://halldweb.jlab.org/wiki/index.php/File:T_offset_c22.gif"
class="image"><img alt="T offset c22.gif"
src="cid:part5.03030307.02050409@jlab.org"
srcset="/wiki/images/thumb/1/12/T_offset_c22.gif/450px-T_offset_c22.gif
1.5x, /wiki/images/1/12/T_offset_c22.gif 2x"
height="180" width="300"></a>
</p>
<p>Each entry in the histograms is from calibration of a
single run. The ADC-TDC time difference is a by-product
of the time-walk correction. Shown is the mean
difference in a run for two channels, 17 and 22. For 22,
which is near the beam, there is a strange instability
in the value. It is not known if this is related to the
the matching inefficiency mentioned above.
Sasha speculated that the effect may be due to small
pulses around the beam line whose times are not well
measured by the ADCs. Beni remarked that it is possible
to check the quality of the ADC time before using it. A
pedestal value of 0 indicates a problem finding a good
time.
</p>
<p>Beni has been talking to Sean about using the TOF
calibration to determine the ADC vs. TDC time offsets
rather than getting the numbers from Mike Staib's global
program. The plan is to make the replacement.
</p>
<p>The energy calibration using tracking and matched
paddle hits is in progress.
</p>
<p>Both of the geometry changes (plane order, gaps) will
be put in for the reconstruction of Spring 16 data,
which starts this Thursday.
</p>
<h3><span class="mw-headline" id="NIM_paper">NIM paper</span></h3>
<p>Beni has started a draft. <a rel="nofollow"
class="external text"
href="https://halldsvn.jlab.org/repos/trunk/publications/GlueXTOF">Find
it in the Subversion repository</a>. He asked the FSU
folks to look over the construction section and expand
it as necessary.
</p>
<p>The plan is to distill parts of this paper and replace
the current section of the TDR on the Time-of-Flight.
</p>
<h3><span class="mw-headline" id="Meeting_Frequency">Meeting
Frequency</span></h3>
<p>We decided to try monthly meetings. That makes the next
one on Thursday, June 28.
</p>
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<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-abbreviated" href="mailto:marki@jlab.org">marki@jlab.org</a>, (757)269-5295
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