GlueX TOF Meeting, May 30, 2017

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GlueX Time-of-Flight Meeting
Tuesday, May 30, 2017
11:00 am EDT
JLab: CEBAF Center, Room F326/327


  1. Announcements
  2. Review of minutes from the previous meeting
  3. Calibration Status
    1. first run calibration done
    2. investigate calibration procedure identify potential improvements (Brad)
      DeltaTVsPaddleNum.png Paddle40.png Paddle18.png
    3. Track position vs tof hit position very linear
      However, left and right side do not necessarily point to zero or same value.
      Tof trackpos vs tofpos p8.jpg Left fit p8.jpg Right fit p8.jpg
  4. Active Dividers
  5. Counter reconfiguration
  6. NIM Paper (Paul)
  7. Action Item Recap



Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2017 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Sasha Ostrovidov
  • JLab: Thomas Britton, Brad Cannon, Mark Ito (chair), Simon Taylor, Beni Zihlmann

Calibration Status

  • Beni reports that the first calibration pass through all runs from Spring 17 is done. He got around the previously reported wall-time problem by running the analyses of mean time and time difference in parallel.
  • Brad is studying some systematics of the current calibration procedure. He has looked at the difference between a single-Gaussian fit (as is done presently) and and a double-Gaussian fit to the time difference histograms. See plots in section 3.2 of the agenda above. The difference is only about 30 ps in the case shown, which was judged acceptably small.
    • There appear to be shoulders on both sides of the accidental peak at Δt=0 in all counters. We discussed their origin, but did not come to firm conclusions.
  • Beni has looked at whether there is any systematic position dependence in the position measured in the TOF via end-to-end timing. He compared the difference in position between charged track projection and the TOF-determined position separately for opposite sides of the beamline. See plots in section 3.3 of the agenda above. He sees good agreement, although there are a few counters which show offsets, relative to charged particle projections, of several tens of picoseconds (position measured in units of Δt, end-to-end).

Active Dividers

The test counter is still in the Hall. Nothing new to report on this project.