The sigma -> gamma gamma Width from Nucleon Electromagnetic Polarizabilities

Abstract

The lightest QCD resonance, the sigma, has been recently fixed in the pi-pi 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 to discriminate 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. Taking into account the uncertainties in the analysis and in the parameter values, our result is Gamma_{pole}(sigma -> gamma gamma) = (1.2 +- 0.4) KeV.

9 pages, 1 figure. v2: Matches published version. v3: Small errata in Eq. (3) corrected

References in corpus (6)

• Note on a sigma model connection with instanton dynamics
• Glueball nature of the sigma/f_0(600) from pi-pi and gamma-gamma scatterings
• Improved dispersion relations for γγ\to π^0π^0
• Two photons into π^0π^0
• Location, correlation, radiation: where is the $\sigma$, what is its structure and what is its coupling to photons?
• Can the gamma-gamma processes reveal the nature of the sigma ?

Cited by in corpus (1)

• Two photons into π^0π^0