Mesons of the f0 family in processes ππ↦ππ, K¯K up to 2 GeV and the chiral-symmetry breaking

Abstract

In a combined analysis of the experimental data on the coupled processes ππ↦ππ, K¯K in the channel with IGJPC = 0+0+ +, the various scenarios of these reactions (with different numbers of resonances) are considered. In a model-independent approach, based only on analyticity and unitarity, a resonance is represented by a pole cluster (poles on the Riemann surface) of the definite type that is defined by the state nature. The best scenario contains the resonances f0(665) (with properties of the σ-meson), f0(980) (with a dominant s¯s component), f0(1500) (with a dominant flavour-singlet, e.g., glueball component) and the f0(1710) (with a considerable s¯s component). If the f0(1370) exists, it has a dominant s¯s component. The coupling constants of the observed states with the considered channels and the ππ and K¯K scattering lengths are obtained. The conclusion on the linear realization of chiral symmetry is drawn.