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Present: M.D., A.D., S.S, J.S.

  • General:
    • we should aim at having a decent version of the proposal by Monday/Tuesday for the GlueX collaboration. We will also send it to theorists, asking for letters of support.
    • Next meeting will be Tuesday March 31st 2020, 8am.
  • MD:
    • Studied the effect of helicity-correlated beam position on the measured asymmetry, and wrote down a paragraph for the proposal.
    • Working on polishing the proposal
    • Produced first results from GEANT4 HDGEANT. The Bremsstrahlung spectrum is still one for a diamond, and there the simulation is still not setup for lower energy photons. First results are shown here:
    • Mark put the proposal on Overleaf

  • JS:
    • Contacted the GlueX collaboration to ask for a review committee to be setup for the proposal.
  • AD:
    • Polished the proposal (now version V8):
      • Added a part on a possible run at lower (tentatively 5.5) energy, see plot here;
      • Rewrote the part on the sensitivity to quark compositeness;
      • Included the various topics we had discussed in GDH meetings;
      • Incorporated our reply to the TAC comments;
      • Made many minor editorial modifications and removed some inconsistencies;
    • Looked into the possibility to run at 1 GeV (to cover the resonance region, including the Δ(1232)).AD add discuss the feasibility with CEBAF people to run 0.5 pass in Hall D and that seemed possible. MD then contacted Jay Benesh to confirm. Here Jay's answer:
      • If you were the only hall running and we could repower the big septa to deal with 1 GeV beam, we could extract 1 GeV beam to hall D. I'm not sure how we'd have to set the quads to blow up the beam enough to keep the diamond intact, but there are enough quads in the line to do it. And there's the little problem that Harwood refused to have any of the dipoles measured at less than 45% of nominal, so we would be steering with BLMs through eight dipoles, but it could be done. When I was designing Hall D I looked at breaking the beam pipe at third or fourth pass, moving magnets vertically, and sending the intermediate energy there. It worked in silicon.
      • Addressing Jay's concerns, AD pointed out that we don't need to worry about the diamond radiator and the beam envelope (the quadrupole issue) is of secondary importance. Thus, it looks like it's not a problem to have 0.5 pass and the idea may not be that crazy. Still, it will probably require some work, but presumably it can be prepared before the experimental run, in a non-obtrusive way for the experimental program (only the north linac need to be on. The arcs and south linac can be off). Then MD pointed out that we would probably have to change the trigger and reduce the solenoid field in order to keep the acceptance high. For the proposal we might need some simulation to show that it is possible. The higher energies are generally understood to be possible by everyone because GlueX has already done them.
    • Will work on:
      • Adding a 50% efficiency below 7.5 GeV in the figures showing the expectations
      • Ask Eugene and Alex Somov what they think about running at 1 GeV (0.5 pass)
      • Add to the proposal a table summarizing the beam time requirements
  • SS:
    • Will look at how much data on the neutron (deuteron) would help with χEFT.
    • Will implement the formula for polarized BH and see how it contaminates the cross section difference.