We determine the branching fractions ${ \mathcal{ B}}$ and $CP$ asymmetries ${ \mathcal{ A}_{ { \it CP}}}$ of the decays $B^+ \rightarrow \pi^+ \pi^0$ and $B^+ \rightarrow K^+ \pi^0$. The results are based on a data set containing 198 million bottom-antibottom meson pairs corresponding to an integrated luminosity of $190\;\text{ fb}^{ -1}$ recorded by the Belle II detector in energy-asymmetric electron-positron collisions at the $\Upsilon (4S)$ resonance. We measure ${ \mathcal{ B}(B^+ \rightarrow \pi^+ \pi^0) = (6.12 \pm 0.53 \pm 0.53)\times 10^{ -6}}$, ${ \mathcal{ B}(B^+ \rightarrow K^+ \pi^0) = (14.30 \pm 0.69 \pm 0.79)\times 10^{ -6}}$, ${ \mathcal{ A}_{ { \it CP}}(B^+ \rightarrow \pi^+ \pi^0) = -0.085 \pm 0.085 \pm 0.019}$, and ${ \mathcal{ A}_{ { \it CP}}(B^+ \rightarrow K^+ \pi^0) = 0.014 \pm 0.047 \pm 0.010}$, where the first uncertainties are statistical and the second are systematic. These results improve a previous Belle II measurement and agree with the world averages.
Categories: hep-ex