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</style><article id="node-361730" class="node node-logentry article ia-n clearfix" role="article"><header class="node-header"><h1 class="node-title" rel="nofollow">
<a href="https://logbooks.jlab.org/entry/3288986" rel="bookmark">CDC Straw Positions</a>
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<p class="author-datetime">
Lognumber <a href="https://logbooks.jlab.org/entry/3288986" class="lognumber" data-lognumber="3288986">3288986</a>. Submitted by <a href="https://logbooks.jlab.org/user/davidl">davidl</a> on <time datetime="2014-07-01T13:17:49-0400" pubdate="pubdate">Tue, 07/01/2014 - 13:17</time>. </p>
<table class="field-vitals"><tr><th>Logbooks: </th><td><a href="https://logbooks.jlab.org/book/hdcdc">HDCDC</a> <a href="https://logbooks.jlab.org/book/hdlog">HDLOG</a></td></tr><tr><th>Tags: </th><td><a href="https://logbooks.jlab.org/tag/detector">Detector</a></td></tr><tr><th>References: </th><td><a href="https://logbooks.jlab.org/entry/3288879">3288879 - CDC straw positions shifted in phi</a><br /><a href="https://logbooks.jlab.org/entry/3288617">3288617 - BCAL, CDC cosmic events</a></td></tr></table></div>
<div class="logentry node-content">
<p>The recent BCAL/CDC cosmic run showed issues with the CDC straw locations. The source of these was identified and fixed in the HDDS. The attached images show a test of the locations using the cosmic data and a straight line fitter implemented as the new DTrackCandidate:CDCCOSMIC factory. Only the positions of the wires were used. Fits were done individually to the axial wires in the XY plane and then to the stereo wire YZ locations as determined by the intersection of the wire with the axial fit. The first pair of plots shows the residuals for all rings when in their nominal positions(left) and the residuals when ring 20 was shifted by 1 straw(right). The plot at the bottom shows a projection of just ring 20 for the case of no shift, shifting by 1 straw, and shifting by 2 straws. Ideally, the residuals should have a sigma of 8mm/sqrt(12) = 2.3mm. The gray in the second plot has a wider distribution, but this may be expected due to the rough nature of the analysis. What this shows is that if the straw indexing were incorrect for any ring, it would be seen in the left side plot in the first figure. It appears though that no rings have any offset and all indexing is now correct.</p>
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