The σ-meson production in excited Υ decay processes:: phenomenological analyses

We analyze the pi pi production amplitudes in the excited gamma decay processes, gamma (2S) --> gamma (1S)pi (+)pi (-), gamma (3S) --> gamma (1S)pi (+)pi (-) and gamma (3S) --> gamma (2S)pi (+)pi (-), and the pi pi and K (K) over bar production amplitudes in the charmonium decay processes, psi (2S) --> J/psi pi (+)pi (-) and J/psi --> phi pi (+)pi (-), phiK(+)K(-), including the possible effect of light a production. The amplitudes are parametrized by the sum of Breit-Wigner amplitudes for the sigma and the other relevant particles and of the direct 2 pi -production amplitude, following the VMW method. All the pi pi (and K (K) over bar) invariant mass spectra are reproduced well with the sigma Breit-Wigner amplitudes by using the common parameters, m(sigma) = 526(-37)(+48) MeV and Gamma (sigma) = 301(-100)(+145) MeV, which is almost consistent with the values obtained in our previous phase shift analyses. (C) 2001 Elsevier Science B.V. All rights reserved.