GlueX Start Counter Meeting, June 29, 2017

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GlueX Start Counter Meeting
Thursday, June 29, 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
    1. Data MC comparison, Example of timing for events with no charged tracks:
      DATA: Sc paddle vs time DATA.gif
      MC: Sc paddle vs time MC.gif
  6. NIM/TDR
  7. Meeting time discussion
  8. 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: Mahmoud Kamel
  • JLab: Mark Ito (chair), Eric Pooser, Simon Taylor, Beni Zihlmann

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

Efficiency and Attenuation

Mahmoud showed updated results on two topics. Please see his slides for the details.


After adjusting his timing cuts for both the signal and the accidental background, efficiency is back to values we have seen before, overall about 97% percent.


The fits to minimum ionizing peaks are now converging nicely. He finds very reasonable results for peak position as a function of z-position in the counter, consistent with expectations from the bench tests at FIU obtained during construction.

There are still four problem counters that have anomalously low statistics. Mahmoud will review whether something may have gone wrong with the timing cut for these counters.


Beni has started looking at comparisons between Monte Carlo and data for the start counter. Above (in the agenda) he plots the time distributions for the 30 counters; data on top, Monte Carlo below. Data is significantly wider and is offset in time from the simulation. This is work in progress; the explanations are not known at this point.

NIM Paper

Eric has received comments on the draft from Werner. He will incorporate them as well as the attenuation plots from Mahmoud when they become available in their final form. He feels on track for the August 1 deadline.

Meeting Time

We will continue to meet at 11:30 am for the next few meetings.