Insights intoQ2Q¯2states from an effective perspective

Ll. Ametller, P. Talavera
2015 Physical Review D  
We discuss the two photon coupling of the lightest scalar meson on the basis of an extension of χPT. Using low energy data on the pion form-factor and the γγ→π^+π^-(π^0π^0) cross-sections as inputs, we find Γ(σ→γγ) 0.126 keV . The smallness of the result and the relative weight between its components, Γ_γγ→ S_1Γγγ→ππ→ S_1 < 1, suggests that the scalar 0^++ meson is mainly a Q^2Q̅^2 state.
doi:10.1103/physrevd.92.074008 fatcat:yiqv5tq6c5borg56hk2hgl7rem