We report the first observation of color-suppressed ${\overline{B}}^0\to D^0{\pi }^0$, $D^{*0\mathrm{}}{\pi }^0$, $D^0\eta$, and $D^0\omega$ decays, and evidence for ${\overline{B}}^0\to D^{*0\mathrm{}}\eta$ and $D^{*0\mathrm{}}\omega$. The branching fractions are $B({\overline{B}}^0\to D^0{\pi }^0)=(3.1\pm 0.4\pm 0.5)\times {10}^{-4\mathrm{}}$, $B({\overline{B}}^0\to D^{*0\mathrm{}}{\pi }^0)=\left({2.7}_{-0.7-0.6\mathrm{}}^{+0.8+0.5\mathrm{}}\right)\times {10}^{-4\mathrm{}}$, $B({\overline{B}}^0\to D^0\eta )=({1.4}_{-0.4\mathrm{}}^{+0.5\mathrm{}}\pm 0.3)\times {10}^{-4\mathrm{}}$, $B({\overline{B}}^0\to D^0\omega )=(1.8\pm {0.5}_{-0.3\mathrm{}}^{+0.4\mathrm{}})\times {10}^{-4\mathrm{}}$, and we set $90\%$ confidence level upper limits of $B({\overline{B}}^0\to D^{*0\mathrm{}}\eta )<4.6\mathrm{}\times {10}^{-4\mathrm{}}$ and $B({\overline{B}}^0\to D^{*0\mathrm{}}\omega )<7.9\mathrm{}\times {10}^{-4\mathrm{}}$. The analysis is based on a data sample of $21.3{\mathrm{fb}}^{-1\mathrm{}}$ collected at the $\Upsilon \left(4S\right)$ resonance by the Belle detector at the KEKB $e^{+}{e}^{-}$ collider.

• Received 15 September 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.052002