Phys. Rev. Lett. 100, 241804 (2008) [4 pages]σ→γγ Width from Nucleon Electromagnetic PolarizabilitiesReceived 13 February 2008; published 20 June 2008 The lightest QCD resonance, the σ, has been recently fixed in the ππ scattering amplitude. The nature of this state remains nowadays one of the most intriguing and difficult issues in particle physics. Its coupling to photons is crucial for discriminating its structure. We propose a new method that fixes this coupling using only available precise experimental data on the proton electromagnetic polarizabilities together with analyticity and unitarity. By taking into account the uncertainties in the analysis and in the parameter values, our result is Γpole(σ→γγ)=1.2±0.4 keV. © 2008 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.100.241804
DOI:
10.1103/PhysRevLett.100.241804
PACS:
11.80.Et, 13.20.Jf, 13.40.Hq, 13.75.Lb
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