a Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94305, USA
b University of Pennsylvania, Philadelphia, PA 19104, USA
Abstract:
The theoretical mechanisms for the decays ψ′ → ψπ0 and ψ′ → ψη, which violate SU2 and SU3, respectively discussed. It is argued that symmetry breaking in the decay amplitudes may be as important as π0 ?η ?η′ mixing. The π0 ?η mechanism ψ′ → ψν → ψπ0 leads to Γ(ψ′ → ψπ0) = (3.3±1.0) × 10?3 Γ(ψ′ → ψν), but this number may be enhanced by a factor as large as 12 by π0?η′ mixing and isospin violation in the decay amplitude. The related decays ψ → ηγ and ψ → η′γ are also discussed.