[Halld-pid] Start Counter Meeting Minutes, December 1, 2016

[Mark Ito]

People,

Please find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_December_1,_2016 
. Mahmoud have a very nice presentation on start counter efficiency.

   -- Mark

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    GlueX Start Counter Meeting, December 1, 2016, Minutes

Present:

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

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


      Efficiency Study

Mahmoud presented an updated efficiency study 
<https://halldweb.jlab.org/talks/2016/SC_meeting_Dec1st_2016.pdf>. He 
started from raw data for these results. Please see his slides for the 
details. Cuts are described and counter-by-counter efficiencies are 
shown. He tried various timing cuts and also considered two cases: one 
where a single sector, identified by a charged track, was interrogated 
for a start counter hit and another where both nearest neighbors were 
also considered. He also compared results with Monte Carlo, using the 
sim1.1 sample.

Two general conclusions:

 1. Start counter efficiency is generally above 95% in all regions of
    the counters.
 2. Efficiency is the same, within 1%, in Monte Carlo data.

Some items from the discussion:

  * Not clear why the time distribution of time difference between the
    start counter and track time[?] is so wide, ten ns or so full width.
  * Werner wondered if we could generate simulated data with various
    perturbations to the geometry to see if we can reproduce some of the
    non-uniformities in efficiency from counter to counter.
  * Another interesting study would be to require a start counter hit in
    a particular counter and look at the charged particle azimuthal
    distribution at the start counter, repeated for all counters and at
    various z-positions. This should give a survey of the counter edges
    and help us refine knowledge of the as-found geometry.

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