GlueX Start Counter Meeting, October 23, 2023

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GlueX Start Counter Meeting
Monday, October 23, 2023
9:00 am EDT

Meeting information:
Benedikt Zihlmann is inviting you to a scheduled ZoomGov meeting.
Topic: Start Counter



present: Simon, Eugene, Hovanes, Igal, Beni

  • Beni did not realize that Igal, Joerg and Vivian are not on the halld-pid mailing list, so they did not know of this meeting.
  • The main topic in the meeting was about the KLF experiment needing a Start Counter Detector
    • the following issues are mentioned
      • KLF beam has a 6cm diameter
      • Start Counter nose cone opening is 4cm in diameter
      • KLF target is 6cm in diameter 40cm long this is 10cm longer the standard GlueX target:
        • LH at 20K 0.07085g/cm^3, at 40cm this is 2.834g/cm^2
        • Plastic scintillator density is of order 1.12 g/cm^3: over a length of about 3cm part of the beam hits the start counter (3mm width paddles) this means more than half of the beam, 5/9, will hit the paddles over a length of 3cm: 1.12*0.3*1.*(5/9) gives an estimated target thickness of 0.18g/cm^2 where the fact that only "half" of the beam hits the detector is already folded in.
        • The large K-beam diameter will contain also a lot of neutrons. What is the impact of these neutrons on the SiPM photo sensors as they are really close to the beam line in this case. Further more this hadron beam will have significant tails as it can not be collimated like a photon beam. This tails may affect the SiPM photo senors adversely degrading the performance.
      • Overall what is needed is a full fledged simulation of the K-beam starting from the Be radiator all the way down the beam line through the pair spectrometer into the target and past the downstream GlueX detectors. This will allow to study particle decays along the beam line that will add to the background traveling along the beam line potentially impacting other detectors like the Start Counter and the CDC.
      • view of Start counter matched hits distribution with respect to GlueX target location and size and the expected KLF beam radius, Vertical axis is radius [cm] where zero is nominal beam line and horizontal axis is z position [cm] along the beam with the GlueX target centered at 65cm.:
        Sc with KLF beam.gif

Action Items

  • Add Igal, Joerg and Vivian to the halld-pid mailing list (DONE)


Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2023 on the JLab CUE. This directory is accessible from the web at .