Model-Independent Confirmation of the σ-Meson below 1 GeV and Indication for the f₀(1500) Glueball

الأصل · EN

In the model-independent approach consisting in the immediate application to the analysis of experimental data of such general principles as analyticity and unitarity, a confirmation of the σ-meson at 665 MeV and an indication for the glueball nature of the f₀(1500) state are obtained on the basis of a simultaneous description of the isoscalar s-wave channel of the ππ scattering (from the threshold up to 1.9 GeV) and of the ππ→ KK process (from the threshold to 1.4 GeV where the 2-channel unitarity is valid). A parameterless description of the ππ background is first given by allowance for the left-hand branch-point in the proper uniformizing variable. It is shown that the large ππ-background, usually obtained, combines, in reality, the influence of the left-hand branch-point and the contribution of a very wide resonance at 665 MeV. The coupling constants of the observed states with the ππ and KK systems and lengths of the ππ and KK scattering are obtained.