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