Experimental consequences of a small mixture of cc̄ in the η′ and η mesons

We show that a small but significant mixing of η and η′ with the pseudoscalar cc? state may explanin the large η and η′ masses, the small mass of the new 2.8 GeV state, the large rates for ψ′ → ψη, ψ → η′γ and ψ → ηψ, the large number of photons in ψ decay, some of the missing decay modes of ψ′ and ψ and the small K/π ratio in ψ′ and ψ decays. We predict that 20–30% of all ψ and ψ′ decays contain an η′. Other tests and one important difficulty are also discussed.