Pion Rescattering in Two-Pion Decay of Heavy Quarkonia

The role of pion rescattering in ππ decay of radially excited heavy quarkonia modeled in terms of a Qππ coupling, is investigated within the framework of the covariant Blankenbecler-Sugar equation. The effects of pion rescattering (or pion exchange) are shown to be large, unless the coupling of the two-pion system to the heavy quarks is mediated by a fairly light scalar σ meson, which couples to the gradients of the pion fields. The Hamiltonian model for the quarkonium states is formed of linear scalar confining, screened one-gluon exchange and instanton induced interaction terms. The widths and energy distributions of the basic decays ψ → J/ψ ππ and Υ → Υ ππ are shown to be satisfactorily described by this model. The implications of this model for the decays of the Υ(3S) state are discussed. [email protected] [email protected]