Troubles with Nonleptonic Charm Decays

Conclusions about weak interactions from nonleptonic $D^0$ decays are completely changed by strong final-state interactions. The suppression of $D^0\to {\overline{K}}^0{\pi }^0$ found in some models is completely reversed to $\Gamma (D^0\to {\overline{K}}^0{\pi }^0)=8\mathrm{}\Gamma (D^0\to K^{-}{\pi }^{+})$ by introduction of experimentally measured $K\pi$ scattering phase shifts in the exotic $I=\frac{3}{2}$ and nonexotic $I=\frac{1}{2}$ amplitudes. The $\frac{K^{+}{K}^{-}}{{\pi }^{+}{\pi }^{-}}$ ratio is very sensitive to meson resonances expected at the $D$ mass. Predictions less sensitive to final-state interactions are discussed.