[Halld-pid] Start Counter Meeting Minutes, June 15, 2017

[Mark Ito]

Please find the minutes below and in their usual location 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_June_15,_2017#Minutes>.

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    Minutes

Present:

  * *FIU*: Mahmoud Kamel
  * *JLab*: Thomas Britton, Mark Ito (chair), Eric Pooser, Simon Taylor

There is a recording of this meeting <https://bluejeans.com/s/niDbe/> on 
the BlueJeans site <https://jlab.bluejeans.com/>.


      Calibration

  * Mahmoud showed progress with determination of the counter
    attenuation lengths from data. He is currently having difficulties
    in having fits converge to the distributions of pulse area in
    various bins of position. Please see the recording for the plots.
    The data themselves looks good. There were various suggestions on
    how to get reliable convergence (e. g., removing pedestal noise peak
    completely from the fit region).
  * Mahmoud also showed updated efficiency measurements. See his slides
    <https://halldweb.jlab.org/talks/2017/Data_Production_Analysis.pdf>
    for the details. His efficiency has dropped compared to previous
    studies, but we think that that may be because the time cut he uses
    to identify accidental background includes a significant amount of
    signal, causing over-subtraction.
  * In the same set of slides he showed the projected intersection
    position of charged tracks with the start counter, for all sectors,
    in the r-z projection. The looser matching cut in the new software
    is manifest.

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