Pi0 Polarizability Meeting Nov 15, 2019

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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. Event generator. Equation for g A -> g pi0 pi0
  2. Primakoff signal rate for He/Be targets (Elton) See discussion below
  3. Contact theorists:
    • Lingyun Dai, Hunan University: Changsha, Hunan, CN (dailingyun@hnu.edu.cn)
    • Serguei Gevorkyan (Ilya)
    • Barbara Pasquini (Rory)

Tentative Agenda

  1. Announcements
  2. Action Items
    • Rory contacted Barbara. She is very busy at the moment, but promised to take a look at our LOI and let us know how she might be able to support our effort.
    • Ilya contacted Serguei. He has difficulty installing Bluejeans, but can be reached via Skype. Serguei suggested that we first formulate the exact questions we are interested in, so he will prepare, and then we can set up a phone or skype meeting to discuss.
  3. Theory update
  4. Rates on Be (Elton)
  5. Other business
  6. Next meeting

Minutes

Attending: Elton, Jose, David, Beni, Alex, Ilya, Mark, Rory, Svetlana

  1. Announcements
  2. Action Items
    • Rory contacted Barbara. She is very busy at the moment, but promised to take a look at our LOI and let us know how she might be able to support our effort.
    • Ilya contacted Serguei. He has difficulty installing Bluejeans, but can be reached via Skype. Serguei suggested that we first formulate the exact questions we are interested in, so he will prepare, and then we can set up a phone or skype meeting to discuss.
  3. Theory update
    • Notes Jose Nov 15
    • Jose walked us through the updated version of his notes.
    • Jose has written the cross section in the lab frame and in the forward limit.
    • For two real photons in gg->pi0pi0, there are 2 hadronic tensors, corresponding to two form factors (A and B).
    • For one real and one Coulomb photon gg_C->pi0pi0, there are 3 hadronic tensors, corresponding to three form factors (A, B and C). Previous calculations have ignored the virtuality of the Coulomb photon.
    • In the low-energy (unpolarized) limit, the polarizabilities are alpha ~ (A+12 m_pi B), beta ~ -A. The interpretation of C is still needed.
    • Jose will continue developing his calculations toward a cross section for polarized photons on a heavy target.
    • Svetlana and Aleks will do a ChipT calculation to one loop with Coulomb photon.
  4. Rates on Be (Elton)
    • Assume 5% target for both Pb and Be. [Note: Ilya checked that the Be target in Gluex is 0.7" (1.78 cm) thick and 1" (2.54 cm) in diameter]
    • Calculations with some parameterizations for Pb and Be, the expected signal rates on Be are about 90% of those expected on a Pb target.
  5. Other business
  6. Next meeting
    • Friday Dec 6, 10 am
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