We report measurements of the branching fraction ($\mathcal{ B}$) and direct $CP$-violating asymmetry ($A_{ CP}$) of the charmless decay $B^{ 0} \to K^0 \pi^0$ at Belle II. A sample of $e^{ +} e^{ -}$ collisions, corresponding to $189.8 fb^{ -1}$ of integrated luminosity, recorded at the $\Upsilon(4S)$ resonance is used for the first decay-time-dependent analysis of these decays within the experiment. We reconstruct about 135 signal candidates, and measure $\mathcal{ B}(B^{ 0} \to K^{ 0} \pi^{ 0})= [11.0 \pm 1.2 (stat) \pm 1.0 (syst)] \times 10^{ -6}$ and $A_{ CP} (B^{ 0} \to K^{ 0} \pi^{ 0})= -0.41_{ -0.32}^{ +0.30} (stat) \pm 0.09 (syst)$.
Categories: hep-ex