We evaluate the contributions of final state interactions (FSI’s) to $J/\psi \to \rho \pi$ and ${\psi }^{\prime }\to \rho \pi$ with various intermediate physical channels. We find that the rescattering of $a_2\rho$ and $a_1\rho$ into $\rho \pi$ can change the $\rho \pi$ production rate substantially, and, therefore, could be an explanation for the long-standing “$\rho \pi$ puzzle.” The FSI effects may also play a significant role for other channels, such as $K^{*}\mathrm{K¯}$ and $f_2\omega$.

• Received 9 August 1996

DOI:https://doi.org/10.1103/PhysRevD.55.1421