The sigma -> gamma gamma Width from Nucleon Electromagnetic Polarizabilities

TL;DR

This paper introduces a novel method to determine the sigma resonance's decay width to two photons using proton electromagnetic polarizabilities, analyticity, and unitarity, providing a more precise estimate of its coupling.

Contribution

It presents a new approach that relies solely on experimental data and fundamental principles to fix the sigma resonance's gamma gamma decay width.

Findings

Decay width Gamma_{pole}(sigma -> gamma gamma) = (1.2 +- 0.4) KeV

Method reduces reliance on model assumptions

Provides a more precise estimate of sigma's photon coupling

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.