GlueX Start Counter Meeting, November 5, 2015

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GlueX Start Counter Meeting
Thursday, November 5, 2015
10:00 am EST
CEBAF Center, Room F326/327


  1. Announcements
  2. Review minutes from the October 1 meeting
  3. Calibration Update
  4. Calibration Challenge and the Start Counter
  5. Run Readiness
  6. DAQ Tasks for Spring 2015 Commissioning Run
  7. 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), Simon Taylor, Beni Zihlmann

There is a recording of this meeting available at .


The current plan is to start running December 4, though there is the usual considerable uncertainty. We will aim to have hot check-out done the Wednesday before Thanksgiving, November 25.


Mahmoud gave us an on recent progress in calibration.

  • Time-Walk Corrections. He is using the "standard" ROOT fitter. It seems to be doing about as well as the custom fitter. He was concerned about not being able to do a check of the correction with a plugin that does not output a ROOT Tree in the context of the Calibration Challenge. Only histograms will be allowed. Checks will have to be done during subsequent passes.
  • Inefficiency at the tip of the nose. The efficiency has been seen to drop as one moves to the far downstream "nose" of the star counter. The worst offender is paddle 7. Mahmoud showed plots measuring the difference in sector number between start counter hits and the prediction from charged particles. For sector 7 the correct sector is predicted correctly less than half the time. At the nose the spatial size of the counters in the azimuthal direction shrinks; prediction is more difficult. This demonstrates that the geometry could use some fine adjustment.
  • Azimuthal orientation of the start counter. There was an apparent rotation of the start counter with respect to its expected rotation of 11.25 degrees from nominal. This is likely an artifact of how the center of each sector, in azimuth, is calculated. Mahmoud will make further checks.