Light scalars, analytical ππ scattering amplitude, the Roy equations, and chiral expansion

Abstract

We build up the ππ scattering amplitude with regular analytical properties in the s complex plane. This amplitude is used to describe simultaneously the data on the ππ scattering, the ϕ → π 0 π 0 γ decay, and the π π → K K ¯ reaction. The chiral shielding of the σ(600) meson and its mixing with the f 0 ( 980 ) meson are also taken into account. The amplitude in the range − 5 m π 2 s 0.64 GeV 2 also agrees with results, obtained on the base of the chiral expansion, the dispersion relations, and the Roy equations. The analysis agrees with the four-quark nature of the σ(600) and f 0 ( 980 ) mesons.