Pi0 Polarizability Meeting Mar 13, 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. Comments on draft proposal
    1. Backgrounds to be simulated
      • Background hits
      • BGGEN (PYTHIA)
      • eta production
  6. Other business
  7. Next meeting

Minutes

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

  1. Announcements
    1. Marc Vanderhaeghen
      • Svetlana met with Marc Vanderhaeghen, Igor Danilkin and also Vladimir Pascalutsa when she was in Germany.
      • They are interested in our project.
      • Jose: We need to refine the analysis in order to connect the ChiPT with the Dispersive Analysis. There should be a kinematic region of overlap and calculations should match in this region.
      • Svetlana: This effort is significant and will take of order a year to complete. We should outline the calculations in the proposal and work on them over the next year.
      • Jose: Proposes that Marc and collaborators add some text to the proposal that describes the impact that this experiment might have on the light-by-light scattering amplitudes.
      • Here is a note that Svetlana passed on to us from Marc:
From: Vanderhaeghen, Univ.Prof.Dr. Marc <vandma00@uni-mainz.de>
Sent: March 9, 2020 11:36 AM
To: Barkanova, Svetlana <sbarkanova@grenfell.mun.ca>
Cc: Aleksejevs, Aleksandrs <aaleksejevs@grenfell.mun.ca>; Danilkin, Dr. Igor <danilkin@uni-mainz.de>
Subject: Re: draft of collaboration talk

Hi Svetlana, hi Alex,

I am responding to your enquiry about the pi0 polarizability and am also forwarding this e-mail to my collaborator Igor Danilkin.

As I briefly told you, the pi+ polarizability which enters also the g-2 extraction is well in agreement between dispersive estimates 
and ChPT (see fig. 28 left panel of our recent review paper, attached showing also the Compass data point). 

However for pi0, the same calculation, is an order of magnitude different (and opposite sign) between Chpt and dispersion relation 
(both the Mainz and Bern dispersive analysis confirm this). 

So it would be a crucial input to have an independent result for the pi0 polarizability. We would indeed be very interested to 
going this effort, and can provide the calculations for this channel.

Cheers,

Marc
  1. Action Items
    • Rory will contact Marc and follow up on this discussion.
  2. Theory update
  3. Experiment update
    • Alex: First official monitoring launch of the PRIMEX-eta data has been completed and the ROOT trees are being created. He will send links to the completed files.
  4. Comments on draft proposal
    1. Backgrounds to be simulated
      • Background hits
      • BGGEN (PYTHIA)
      • eta production
    2. Experiment optimization
      • Target position (Beni)
      • Generate angular distributions for some other targets to compare to Pb
    3. Significance of experiment
      • The expected uncertainties of the extracted gg->pi0pi0 cross section (Fig. 24 of proposal) need to be verified and studied more carefully
  5. Other business
  6. Next meeting
    • Next meeting: Friday, March 27, 10 am.