[Halld-offline] Start Counter Meeting Minutes, January 29, 2015

[Mark Ito]

Please find the minutes below and at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_January_29,_2015#Minutes 
. Note that these are minutes from a week ago.
_____________________________________________


GlueX Start Counter Meeting, January 29, 2015
Minutes

  * *FIU*: Werner Boeglin, Mahmoud Kamel
  * *JLab*: Eugene Chudakov, Mark Ito (chair), Eric Pooser, Simon Taylor


Calibration

  * Mahmoud continues to work on the timing calibration.
  * Eric is writing a plugin that selects two paddles with exactly one
    hit each to measure time resolution.
  * Eric is also starting to look at measuring efficiency.
  * Werner remarked that we need to associate a start counter hit with a
    track for many of these studies. Eugene noted that we could survey
    the start counter using tracks to check the position of the
    counters. We could also start using the tagger to nail down timing.
  * The anomaly at 180 degrees in phi remains.
  * Simon found the cause of the vertical bands (lines of constant z) in
    the distribution of intersection points between tracks and the start
    counter when projected in the r-z plane. They are coming from
    particles at forward angles that miss the start counter. The
    algorithm often breaks down in these cases.
  * Simon also understands the "fuzz" in the distribution on the
    downstream side of the nose section. This comes from an overly
    generous cut in phi to associate tracks with a counter. Matches with
    a counter far from the track in phi put the intersection point
    outside the counters.


Mounting ST to Hydrogen Target

Eric showed some slides 
<https://halldweb1.jlab.org/talks/2015/Mounting_ST_to_H2_Target.pdf> 
illustrating a mechanical problem discovered when an attempt was made to 
mount the start counter to the hydrogen target cart. Bolt heads on the 
target cart interfere with the start counter mounting flange. The flange 
on the target cart is glued to the scattering chamber[?] and is not 
easily replaced. The solution is not clear at this point. We agreed that 
we should resist and drilling or grinding on the start counter assembly.

We will talk to Tim to make sure he is in the loop in coming up with a 
solution and express our opinion that the start counter should be left 
alone.

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  * This page was last modified on 6 February 2015, at 19:15.

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