GlueX Start Counter Meeting, December 12, 2019

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GlueX Start Counter Meeting
Thursday, December 12, 2019
10:00 am EST
CEBAF Center, Room L207
BlueJeans: 556 286 544


  1. Announcements
  2. Review minutes from the last meeting
  3. Calibration and Efficiency
  4. Dark Rate Studies
  5. Other Run Planning
  6. Action Item Review


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2019 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Sean Dobbs
  • JLab: Rupesh Dotel, Mark Ito (chair), Simon Taylor, Beni Zihlmann

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

Review of Minutes from October 31

We went over the minutes without a lot of comment.

Calibration and Efficiency

Calibration Incident

We discussed the issue that Sean raised at yesterday's Production and Analysis Meeting. Calibration constants for correction of propagation times were overwritten about a year ago. The effects do not appear to be large, but are visible when looking at resolution as a function of z. Sean has yet to quantify the effect, but we know that it is present in all of the reconstruction of 2018 data done this year.

The problem was introduced inadvertently, probably during the process of a collaborator learning how the calibration database works. We discussed what steps could be taken to prevent, or at least reduce the probability, of this happening again. There is no solution that is at the level flipping some appropriate switch in the system. Restrictions have benefits but also costs in implementation, management, and loss of efficiency in making calibration changes. That said, something will have to be done in the near future.

Realistic Start Counter Efficiency in mcsmear

Sean brought up the issue in incorporating start counter efficiency as a function of z into the simulation. Mahmoud Kamel has performed studies on this in the past. Sean suggested he could perhaps write a short note summarizing his findings that we could use as a guide in coding. Mark will ask Mahmoud about this.

Dark Rate Studies

At a previous meeting Rupesh agreed to take over doing dark rate measurements about every two weeks during the run. As a first step Beni will write up the procedure (or find the already-written-but-temporarily-lost procedure) and go over it with Rupesh.