GlueX TOF Meeting, March 31, 2015

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GlueX Time-of-Flight Meeting
Tuesday, March 31, 2015
11:00 am EDT
JLab: CEBAF Center, Room F326/327


  1. Announcements
  2. Review of minutes from March 18
  3. Calibration Status (Sasha)
  4. Reconstruction Status (Sean)
  5. Running at 5 GeV (all)
  6. Preparations for Spring Run (All)
  7. Meeting participation:
    1. Daily Planning Meeting
    2. Bi-Weekly Calibration Meeting



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 .



  • FSU: Brad Cannon, Paul Eugenio, Aristeidis Tsaris
  • JLab: Mark Ito (chair), Beni Zihlmann
  • NU: Sean Dobbs

Running at 6 GeV

We discussed implications for the TOF of running at lower energy.

  • At lower energy there will be more of the kaon spectrum in the range where the TOF is useful.
  • The pattern of rates near the beamline will be different. This will throw off any rate studies.
  • At lower energy using the FCAL for a trigger may be more difficult. The TOF can be used in coincidence to help.
  • For most of our other goals data with lower energy should not affect things. In particular, most calibrations can go forward.

TOF Matching with Charged Tracks

Sean showed some plots showing how well track matching is being performed for the Fall data. See his slides for details.

He showed a set of plots for each of two conditions, one set with the nominal 6 cm miss distance criterion and one set with the cut relaxed to 20 cm. There is marked improvement with the wider cut, giving us confidence that better channel-to-channel time calibrations will improve the situation greatly.


Beni and Simon Taylor are working on a quick-and-dirty calibration. Beni has passed constants to Simon and they are discussing how to incorporate them into the reconstruction.

Beni is seeing a systematic variation, from the inner paddles to the outer paddles, where uncalibrated times trend later on the outside, from 5 to 10 ns. This is not understood at present.

Online Monitoring

Beni has checked in additional online monitoring plots. These will support his calibration scheme and as such may get us started with online TOF calibrations.