GlueX Start Counter Meeting, June 1, 2017

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GlueX Start Counter Meeting
Thursday, June 1, 2017
11:30 am EDT
CEBAF Center, Room F326/327


  1. Announcements
  2. Review minutes from the last meeting
  3. Calibration
  4. Time-dependent geometry adjustments
  5. Mcsmear procedure and parameters for the start counter
  6. NIM/TDR
  7. Action Item Review




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 .



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

There is a recording of this meeting on the BlueJeans site.


Thomas mentioned that he and Dmitry have started developing a new 3D event display programs. He encouraged us to start thinking about how we would like to visually represent the start counter and its hits.

Review minutes from the last meeting

We went over the minutes from the meeting on April 20.

Most of the discussion was on geometry.

  • The current geometry is based on an idealized geometry from before construction was completed. It is does not reflect the details of the support structure as built.
  • There are small rotations and translations done in the HDDS XML file to make the adjustments suggested by surveys.
  • There are accurate engineering drawings that we can use to bring the geometry closer to reality.
  • Werner pointed out that if we want to do studies of acceptance, we will need to do studies of efficiency as a function of non-ideal displacements/rotations. It would be great to have a parametric way of achieving this.


A complete draft of the NIM paper is done. The folks at FIU are reviewing the text and creating new figures for it based on Spring 2016 data.


Mahmoud has been working on measuring attenuation as function of position using data. The constants we have been using for reconstruction thus far are based on bench measurements at FIU. See his slides for details and plots.

He measures the position of the minimum ionizing peak as a function of z in the start counter as predicted by charged particle tracks. The overall behavior is consistent with what we expect from the bench measurements. There were suggestions for improvements including for example, using finer bins in z.