GlueX Start Counter Meeting, August 3, 2015

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GlueX Start Counter Meeting
Monday, August 3, 2015
10:00 am EDT
CEBAF Center F326/327


  1. Announcements
  2. Review minutes from the July 2 meeting
  3. Calibration
    • plan or timeline for documenting the calibrations and wrapping the procedures so that we can easily run them on new data (Sean)
    • Calibration Update
  4. DAQ Tasks for Spring 2015 Commissioning Run
  5. Action Item Review




Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2015 on the JLab CUE. This directory is accessible from the web at .



  • FIU: Werner Boeglin, Mahmoud Kamel
  • JLab: Mark Ito (chair), Eric Pooser, Simon Taylor, Beni Zihlmann
  • NU: Sean Dobbs

Plans for Automating Calibrations

Eric noted that the next step was to write a GlueX Note describing the current calibration procedures. He will also discuss plans with Mahmoud. We will discuss the issue again next time.

Start Counter Efficiency

Mahmoud has refined the efficiency measuring procedure. He changed the plug-in to use only one candidate from each charged track, the one with the highest figure-of-merit. The efficiency improves from about 84% to about 97%.

Mahmoud will give us a presentation on this topic at the next meeting.


Eric gave a detailed presentation of all aspects of the calibration procedure he has settled on. See his slides for details.

He covered three main areas:

  1. Time-Walk Corrections
  2. Attenuation Corrections
  3. Propagation Time Corrections

The secretary will not attempt to summarize all 60-some slides in this space. The talk itself serves as a document of what was tried and what has worked.

There was discussion throughout the presentation and we did come to some conclusions about further work:

  • Time-Walk Corrections. These look to be in good shape. No further work is anticipated as far as developing procedures is concerned.
  • Attenuation Corrections. We need to control for particle ID, momentum, and angle of incidence before looking at the energy response of the detector.
  • Propagation Time Corrections. The application of an effective propagation velocity also requires a different time offset for each region (straight, bend, nose).

Eric will be working with Simon to incorporate the best constants, as currently calculated, into the CCDB and the reconstruction.