An Explanation for the $\mathit{\rho }-\mathit{\pi }$ Puzzle of $\mathit{J}/\mathit{\psi }$ and ${\mathit{\psi }}^{\prime }$ Decays

We propose a new explanation for the long-standing puzzle of the tiny branching fraction of ${\psi }^{\prime }\to \rho \pi$ relative to that for $J/\psi \to \rho \pi$. In the case of $J/\psi$, we argue that this decay is dominated by a higher Fock state in which the $c\overline{c}$ pair is in a color-octet ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ state and decays via the annihilation process $c\overline{c}\to q\overline{q}$. In the case of the ${\psi }^{\prime }$, we argue that the probability for the $c\overline{c}$ pair in this higher Fock state to be close enough to annihilate is suppressed by a dynamical effect related to the small energy gap between the mass of the ${\psi }^{\prime }$ and the $D\overline{D}$ threshold.