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Title: Pion polarizabilities from a γ γ π π analysis

Here, we present results for pion polarizabilities predicted using dispersion relations from our earlier Amplitude Analysis of world data on two photon production of meson pairs. The helicity-zero polarizabilities are rather stable and insensitive to uncertainties in cross-channel exchanges. The need is first to confirm the recent result on $$(\alpha_1-\beta_1)$$ for the charged pion by COMPASS at CERN to an accuracy of 10% by measuring the $$\gamma\gamma\to\pi^+\pi^-$$ cross-section to an uncertainty of ~1\%. Then the same polarizability, but for the $$\pi^0$$, is fixed to be $$(\alpha_1-\beta_1)_{\pi^0}=(0.9\pm0.2)\times 10^{-4}$$ fm$$^{3}$$. By analyzing the correlation between uncertainties in the meson polarizability and those in $$\gamma\gamma$$ cross-sections, we suggest experiments need to measure these cross-sections between $$\sqrt{s}\simeq 350$$ and 600~MeV. The $$\pi^0\pi^0$$ cross-section then makes the $$(\alpha_2-\beta_2)_{\pi^0}$$ the easiest helicity-two polarizability to determine.
 [1] ;  [2]
  1. Institut fur Kernphysik and Julich Center for Hadron Physics, Forschungszentrum Julich, Julich (Germany); Indiana Univ., Bloomington, IN (United States)
  2. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); College of William and Mary, Williamsburg, VA (United States)
Publication Date:
Report Number(s):
JLAB-THY-16-2386; DOE/OR/23177-4002; arXiv:1611.14441
Journal ID: ISSN 2470-0010; PRVDAQ; TRN: US1701067
Grant/Contract Number:
SFB/TR 110; AC05-06OR23177
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 94; Journal Issue: 11; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; pion polarizability; dispersion relations; partial-wave analysis; Chiral Lagrangian; meson production
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1338122