Existence of the σ meson below 1 GeV and chiral symmetry -: art. no. 054024

On the basis of a simultaneous description of the isoscalar s-wave channel of pi pi scattering (from the threshold up to 1.9 GeV) and the pi pi-->K (K) over bar process (from the threshold to similar to1.4 GeV where the 2-channel unitarity is valid), a confirmation of the sigma meson at similar to 665 MeV and an indication for the glueball nature of the f(o)(1500) state are obtained. These results are achieved in the model-independent approach consisting of the immediate application of such general principles as analyticity and unitarity to the analysis of experimental data. A parameterless description of the pi pi background is first given by allowance for the left-hand branch Feint in the proper uniformizing variable. It is shown that the large pi pi background, usually obtained, combines, in reality, the influence of the left-hand branch point and the contribution of a wide resonance at similar to 665 MeV. The coupling constants of the observed states with the pi pi and K (K) over bar systems and lengths of the pi pi and K (K) over bar scattering are obtained. The existence of the f(o)(665) state and the obtained ir rr-scattering length (a(o)(o) = 0.27 +/- 0.06,[m(pi+)(-1)]) seem to suggest the linear realization of chiral symmetry.