Implications of Recent $\overline{B}^0\to D^{(*)0}X^0$ Measurements

The prediction of the branching ratios for the color-suppressed modes $\bar B^0\to D^{(*)0}X^0$ ($X=\pi,\eta,\omega$) based on factorization is too small compared to recent measurements even after large nonfactorizable corrections to hadronic matrix elements are included. This implies the relevance of final-state interactions (FSIs): The color-suppressed mode receives a sizable feedback from the color-allowed mode $\bar B^0\to D^{(*)+}\pi^-$ via isospin FSIs. Even with a small isospin phase difference of order $25^\circ$ the decay rate of $\bar B^0\to D^0\pi^0$ can be enhanced by FSIs by a factor of 3. It is found that $a_2$ is not universal: $a_2(D\pi)>a_2(D^*\pi)$. We conjecture that inelastic final-state scattering effects induced by resonances and quark exchange that mimic annihilation and color-suppressed tree topologies, respectively, may account for the discrepancy between theory and experiment for $\bar B^0\to D^{(*)0}(\eta,\omega)$ decays.