Pi0 Polarizability Meeting Mar 6, 2020

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Meeting Information

Meeting Time And Location

10:00 am ET (JLab time)

CC F228


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Action Items

  1. ChiPT calculation to one loop with Coulomb photon (Svetlana and Aleks)

Tentative Agenda

  1. Announcements
  2. Action Items
  3. Theory update
  4. Experiment update
  5. Work list for the draft proposal to collaboration
    • Clarification to questions from the PAC where possible
    • Update to theory section (Jose and Mark)
    • Sensitivity of cross section to polarizabilities
      • Jose: The sensitivity is determined by extrapolating into the kinematic region for polarizabilities and will take effort. For now, we will use the estimates from Dai/Pennington.
    • Initial optimization of experiment (e.g. target position)
      • This item will not be attempted for the proposal draft.
    • Analysis of PRIMEX data (Ilya)
    • Assessment of nuclear coherent background (Elton)
      • What is the t-dependence of the sigma (500)?
  6. Theory Appendix from Jose
  7. Other business
  8. Next meeting


Note: I am writing these notes from memory without good notes and memory might not be accurate.
Attending: Jose, Mark, Elton, Ilya, Rory

  1. Announcements
    • Goal is to have a all input to the draft proposal by next Wednesday so it can be reviewed and submitted by next Friday.
  2. Action Items
  3. Theory update
    • Update to theory section of proposal. Expect to have a draft of an appendix with more details by next Wed.
  4. Experiment update
    • Signal cross sections (Ilya)
    • Ilya has used the FF taken from single pi0 calculations and used to estimate cross sections for 2pi0. Replace longitudinal momentum transfer qL ~ mpi -> 2mpi, and scattering of pi0 in final state -> 2x scattering for 2 pi0.
    • Calculation of FF shows oscillations that require increased precision and Ilya has increased granularity and computing time. Glauber calculation includes final-state absorption and computes real and imaginary part of FF.
    • Comparing to Elton's estimate (in the draft): Elton's estimate was 345 nb at 6 GeV. Using pi0 FF, Jose's sigma(gg-pi0pi0) and 5.5-6 GeV range Ilya gets sigma=200 nb -> at 6 GeV sigma=212 nb -> Use Elton's sigma(gg->pi0pi0) sigma=270 nb. Remaining difference is due to FF. Average for the proposal; use the estimate of 300 +/- 50 nb.
  5. Updates to proposal
    • Ilya added a section on the Primex-eta analysis
    • Rory added a paragraph describing the state-of-the-art polarizability measurements (proton and pi+), which was added to the introduction
    • The theory support is added separately from other authors on the collaboration list
    • Added Sergey and Lingyung to the theory list (in addition to Jose, Svetlana and Aleks) They were happy to be included.
    • Added title CPP/NPP to table of run conditions
    • Added comment that the cross section is model dependent
    • Corrected typo in sensitivity section
    • Modified precision goals in abstract to agree with sensitivity and summary
    • Theory Appendix from Jose
  6. Other business
  7. Next meeting