GlueX Start Counter Meeting, December 1, 2016

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GlueX Start Counter Meeting
Thursday, December 1, 2016
11:00 am EST
CEBAF Center, Room F326/327


  1. Announcements
  2. Review minutes from the last meeting
  3. Calibration/Efficiency Update (Mahmoud)
  4. Run Readiness
  5. NIM/TDR
  6. Action Item Review




Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2016 on the JLab CUE. This directory is accessible from the web at .



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

There is a recording of this meeting on the BlueJeans site.

Efficiency Study

Mahmoud presented an updated efficiency study. 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.