GlueX Start Counter Meeting, June 2, 2016

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GlueX Start Counter Meeting
Thursday, June 2, 2016
10:00 am EDT
CEBAF Center, Room F326/327


  1. Announcements
  2. Review minutes from the last meeting
  3. Calibration Update
  4. NIM/TDR
  5. 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: Mark Ito (chair), Eric Pooser, Simon Taylor, Beni Zihlmann


Simon is close to submitting a pull request with new geometric parameters for the start counter. He is currently dealing with an overlap issue with the CDC. He is using the recently done survey as a guide for the changes. It shows a tilt larger than we thought we had, 0.3 degrees down. (For comparison we had 0.6 degrees in Fall 2014.) On the upstream end the start counter is 3.4 mm above nominal.

Simon is also working on widening the cut for matching charged tracks to the start counter in the nose region. Previous studies have shown the phi distribution of tracks at the intersection with the start counter not centered on the nominal counter center. The shift is not always in the same direction.


After working with Sean to correct the propagation time calibration implementation, Mahmoud measured time resolution for three representative runs.

Run Sigma (ps)
11366 286
11405 284
11455 293

He tried running with run-by-run calibrations and did not see an improvement over the single set of constants already present in the CCDB (improvement of 3 ps). We will go ahead and use the single set.


Mahmoud showed start counter hit efficiency using crossing charged tracks. If he requires more than 20 hits on the charged track, the efficiency goes up to 99%. Unfortunately, there are not enough tracks in the forward part of the nose that satisfy this criteria to get a meaningful efficiency measurement there.


Eric is back in action in Newport News and will be working on the NIM paper.

Swiss Efficiency

Beni noted that the Gotthard Base Tunnel was recently completed on time and under budget, apropos of nearly nothing.