GlueX Start Counter Meeting, February 8, 2018

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GlueX Start Counter Meeting
Thursday, February 8, 2018
10:00 am EST
CEBAF Center, Room L207
BlueJeans: 556 286 544


  1. Announcements
  2. Review minutes from the meeting on January 11
  3. Calibration and Efficiency
  4. Time-dependent geometry adjustments
  5. NIM/TDR
  6. Action Item Review




Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2018 on the JLab CUE. This directory is accessible from the web at .



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

There is a recording of this meeting on the BlueJeans site. Use your JLab credentials to authenticate.

Review minutes from the meeting on January 11

We went over the minutes without significant comment.

Calibration and Efficiency

Mahmoud showed slides on his recent work analyzing 2018 data. Please see the slides for plots and details.

  • In general, calibration constants are close to those obtained for Spring 2017.
  • Propagation time evaluation plots were shown, using the old constants. Results in all sections (nose, bend, and straight) are flat, but an offset from zero is visible.
  • Overall time resolution is a bit worse than he has seen before; 314 ps now vs. 280 ps before.
  • Overall efficiency for 2018 data comes out at 97%.
  • For efficiency from simulated data he gets 99%,
  • Interestingly, the treads in variations in efficiency sector-to-sector seem to match between data and Monte Carlo. Likely Simon did a good job in characterizing the non-ideal geometry of the start counter.


The NIM paper is still out for comment from the Collaboration. So far only two collaborators have offered suggestions (thanks Simon and Sascha Somov). Collaborators are encouraged to read it and comment. The paper can be found here.