Existence and Properties of the $f_0(665)$ State and Chiral Symmetry

Abstract

On the basis of a simultaneous description of the isoscalar s-wave of $\pi \pi$ scattering (from the threshold up to 1.9 GeV) and of $\pi \pi \to K\bar{K}$ process (from the threshold to $\sim$ 1.4 GeV) in the model-independent approach, it is shown that there exists the $f_0(665)$ state with properies of the $\sigma$-meson, the glueball nature of $f_0(1500)$ is indicated, and the $f_0(1370)$ is assigned mainly to $s\bar{s}$ state. The coupling constants of the observed states with $\pi \pi$ and $K\bar{K}$ systems and scattering lengths $a_0^0(\pi \pi )$ and $a_0^0(K\bar{K})$ are calculated. The existence of the $f_0(665)$ state and the obtained $\pi \pi$-scattering length ($a_0^0\approx 0.27m_{{\pi }^{+}}^{-1}$) seem to suggest the linear realization of chiral symmetry.

Comments: 7 pages, LaTex; Talk given at the XV-th Int'l Seminar on High Energy Physics Problems "Relativistic Nuclear Physics & Quantum Chromodynamics" (Dubna, 25-30 September, 2000)