Forbidden decaysψ′→η+ψandψ′→π0+ψ

It is proposed that the SU(3) violation in the decay ${\psi }^{\prime }\to \eta +\psi$ arises from the proximity of the $\overline{D}D$ threshold to the ${\psi }^{\prime }$ mass in contrast to the $\overline{F}F$ threshold. In this case the $D^{+}-D^0$ mass splitting leads to the SU(2)-violating decay ${\psi }^{\prime }\to {\pi }^0+\psi$, which is calculated to have a rate not far below its present experimental limit.