JEF meeting, August 27, 2021

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Meeting time and location= 9:30 am EST (JLab time) Bluejeans only

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  • SICCAS crystals
  • Module fabrication
  • COMCAL tests, TAC running, etc.
- Adjusting LED system for CCAL -- Sasha
  • Data analysis
- 2π0 and 2η studies -- Annika Thiel
- \eta \to \gamma\gamma\pi^0
  • Simulations


Attendees: Bill B., Olga, Phil, Zisis, Arshak, Jon, Susan, Azizah, Igal, Annika, Liping, Sasha, Jane, S.T.

  • SICCAS received shipment of new raw material, producing test crystals now; plan to wait ~2 weeks for results
    • Powder from previous vendor --> poor quality crystals
    • Delivery schedule is still unknown
  • COMCAL has been installed on platform and re-surveyed
    • Still tilted but not as badly as before
    • Sasha checked out COMCAL response using LED and alpha source
      • LED response using amplitudes wider distribution than expected (hoped for?)--> spread in light distribution
    • Adjusted HV, checked timing --> things are starting to look good
  • Light uniformity from LMS is a concern for FCAL-II; plan to use different LED colors just like done for FCAL
  • Fernando has prototype for PMT divider for NPS, working on tuning design for them, then for us
    • Hope to test during upcoming runs, can even be during CPP next year, but want to set a deadline for the middle of next year
  • Igal gave an update on his η→π0γγ analysis
    • Ran simulations for both GlueX and JEF conditions
      • Observed considerable peaking background from η→2γ, probably arising from conversions/split-offs
        • Looked at ways to reduce or eliminate this contamination
    • Found expected number of π0γγ events to be roughly consistent with the JEF proposal
    • Found the amount of beam time needed for production of 50M ηs with recoil proton required to be roughly an order of magnitude longer than the proposal estimate
      • Offline discussion summary:
        • Clarify the meaning of 50M tagged eta i.e. eta with a detectable recoil proton (eta can possibly not pass the selection criteria)
        • Out of 50M tagged eta, 1/4 is expected to pass the selection criteria
        • Expected integrated luminosity for phase IV is 315 pb-1 ie for 100 PAC days, ~ 1fb-1 should be collected
        • After re-compiling all numbers, the signal observed is consistent with simulation expectation
    • Found that the kinematic fit is distorting the mass distributions (sometimes moving peaks away from the physical mass values)
    • TMVA results briefly touched on, but signal after applying cut on BDT response seems high possibly due to a bug in DSelector that is treating g1g2 and g2g1 as two different combination
  • Annika presented some results of her γp→p2π0,p2η analysis
    • Background in 2η channel is high, but reduced by imposing a π0 veto
    • Handled background by looking at side-band regions in 2D
    • See considerable 2π0 strength at low mass consistent with f0(500)
    • We had a discussion regarding simulation of these events
      • Annika currently using genr8, looked into using amptools without much success
      • Use mass distributions from data?