Scalar Dipion States Produced in Heavy Quarkonium Decays and the Final State Interaction

We study phenomenologically the invariant mass spectra of scalar dipion states produced in cascade decays of excited $\mathrm{{\rm Y}}$ and $\psi$, and $J\mathrm{/}\psi$ decays into light vector meson. Dipion production amplitude is given as a product of the Born term and an effective scalar form factor written in terms of a unitarized chiral theory. The model reproduces the experimental mass spectra very well.