We measure the branching fractions and $CP$ asymmetries for the decays $B^{ 0}\to \bar{ D}^{ 0}\pi^{ 0}$ and $B^{ +}\to \bar{ D}^{ 0}\pi^{ +}$, using a data sample of $772\times 10^{ 6}$ $B\bar{ B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^{ +}e^{ -}$ collider. The branching fractions obtained and direct $CP$ asymmetries are $\mathcal{ B}(B^{ 0}\to \bar{ D}^{ 0}\pi^{ 0}) = [2.70 \pm 0.06~ \text{ (stat.)} \pm 0.10~ \text{ (syst.)}] \times 10^{ -4}$, $\mathcal{ B}(B^{ +}\to \bar{ D}^{ 0}\pi^{ +}) = [4.53 \pm 0.02~ \text{ (stat.)} \pm 0.15~ \text{ (syst.)}] \times 10^{ -3}$, $ { \cal A}_{ CP}(B^{ 0}\to \bar{ D}^{ 0}\pi^{ 0}) = [+0.42 \pm 2.05~ \text{ (stat.)} \pm 1.22~ \text{ (syst.)}]\%$, and $ { \cal A}_{ CP}(B^{ +}\to \bar{ D}^{ 0}\pi^{ +}) = [+0.19 \pm 0.36~ \text{ (stat.)} \pm 0.57~ \text{ (syst.)}]\%$. The measurements of $\mathcal{ B}$ are the most precise to date and are in good agreement with previous results, as is the measurement of ${ \cal A}_{ CP}(B^{ +}\to \bar{ D}^{ 0}\pi^{ +})$. The measurement of ${ \cal A}_{ CP}$ for $B^{ 0}\to \bar{ D}^{ 0}\pi^{ 0}$ is the first for this mode, and the value is consistent with Standard Model expectations.
Categories: hep-ex