GlueX TOF Meeting, October 10, 2018

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GlueX Time-of-Flight Meeting
Wednesday, October 10, 2018
10:00 am EDT
JLab: CEBAF Center, Room F226
BlueJeans Meeting number is 350 531 998


  1. Announcements
  2. Review of minutes from the August 15 meeting
  3. Calibration Status
  4. Upgrade Plan
  5. NIM Paper (Paul)
  6. Action Item Recap


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 .



  • JLab: Thomas Britton, Ashley Ernst, Mark Ito (chair), Simon Taylor, Beni Zihlmann

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


Ashley will be taking on the role of FSU TOF person at JLab. To start, she is going to work on the calibration of the Fall 2018 data. She has been talking to Beni about this and reviewing the code. Great news!

Review of minutes from the August 15 meeting

We glanced at the minutes. No significant comments were offered.

Calibration Status

  • Sean Dobbs has written the group: TOF calibration skims are ready.
  • Beni reports that the Spring 2018 TOF constants are not doing too badly with the Fall 2018 data as judged from monitoring plots.

Upgrade Plan

We skimmed through the talk Paul Eugenio gave at the collaboration meeting on re-configuring the inner portion of the TOF. In it, he showed an "Option #2" that is less different from the current configuration than Option #1 presented at a previous meeting. In particular, it simplifies the design of a new light guide arrangement by having fewer consecutive "half-width" paddles in the array. The cost is also much less.

Beni is continuing study of the amplified base, but he is not optimistic that it will solve our high-rate-on-inner-counters problem.

We all agreed that Option #2 has a lot to recommend it and should be pursued immediately. Mark will talk to Paul to get more details on how to proceed.

Lucite Shield and Geometry

Thomas reported a visit he received from Jon Zarling asking about whether or not the Lucite shield was present in the Monte Carlo. Jon is doing an FCAL efficiency study for data and for Monte Carlo and the shield could affect things. At one point Thomas had put the shield into the geometry and run Monte Carlo with the revised geometry, but that study did not get completed.

Ashley was tasked with picking up where Thomas left of and finish putting the shield in the standard geometry.

Beni recalled that Brad Cannon had presented, at a Collaboration Meeting, results of rate studies before and after installation of the shield in the Hall. Mark remembered that Paul had also presented results at a TOF meeting.

Working Group Re-Organization and Work Packages

We discussed the proposal from the Collaboration Board on the re-organization of working groups and the associated set of work packages. From the discussion:

  • As Mark mentioned at the collaboration meeting, there is still a role for the individual detector working groups on subjects from hardware to calibration.
  • Thomas pointed out that a lot of the people who might form the new PID working group are the same ones attending the current TOF, Start Counter, and DIRC working group meetings.
  • Beni suggested making a list of new grad students to work on the packages.
  • The proposed work packages are of two types: (1) detector-specific understanding of performance and (2) an overall PID system.
  • PID for GlueX needs a global philosophy for combining information from all detector elements. This is a common practice across many experiments (Beni described the Hermes scheme, Thomas the LHC-B scheme).
  • A new PID working group could design this system. It should be formed with folks who have experience with the idea. Until a design is in place, writing detailed work packages staffed with "workers" might be premature.
  • Thomas and Simon mentioned that there is already a form of this idea in the PID FOM. It makes a combined χ2 from the TOF and tracking dE/dx information.
  • Error estimation is essential as input to any global scheme. Here the detector working groups might be the best place to host the work.