Title screen

[The effect of processes pi pi -> pi pi, K antiK, eta eta in decays of the Psi- and Upsilon-meson families]

[References: 40 tit.]

The effect of isoscalar S-wave processes ππ > ππ ; K K ; ηη is considered in the analysis of data (from the Argus, Crystal Ball, CLEO, CUSB, DM2, Mark II, Mark III, and BES II Collabora- tions) on decays of the charmonium – J = ψ > φ ( ππ ; K K ) and ψ ( 2 S ) > J = ψππ – and of the bottomonium – γ ( 2 S ) > γ ( 1 S ) ππ , γ ( 3 S ) > γ ( 1 S ) ππ and γ ( 3 S ) > γ ( 2 S ) ππ . The analysis, which is aimed at studying the scalar mesons, is performed jointly considering the multi-channel pion-pion scattering, which is described in our model-independent approach based on analytic- ity and unitarity and using an uniformizing variable method, and the decays under reasonable assumptions. Results of the analysis confirm all our earlier conclusions on the scalar mesons. It is also shown that in the final states of the ψ and γ -meson family decays (except for the ππ scattering) the contribution of the coupled processes, e.g., K K > ππ , is important even if these processes are energetically forbidden. This is in accordance with our previous conclusions on the wide resonances. E.g., a new and natural mechanism of destructive interference in the decay γ ( 3 S ) > γ ( 1 S ) ππ is indicated on the basis of that consideration, which provides a characteristic two-humped shape of the di-pion mass spectrum.