Rediscovery of $B^0 \to \pi^0 \pi^0$ at Belle II
2021
We report on the first reconstruction of the $B^{0} \to \pi^{0} \pi^{0}$ decay mode at Belle II. We use samples of 2019 and 2020 data corresponding to 62.8 \invfb of integrated luminosity. We find $14.0^{+6.8}_{-5.6}$ reconstructed events, corresponding to a statistical significance of 3.4 standard deviations and a Branching Ratio, $\mathcal{B}$, of $\mathcal{B}(B^0 \to \pi^0 \pi^0) = 0.98^{+0.48}_{-0.44} \pm 0.27 \times 10^{-6}$. In addition we find $295 \pm 31$ reconstructed events in the $B^{0} \rightarrow D^0(\rightarrow K^- \pi^+ \pi^0) \pi^0$ control mode, which is consistent with expectations. The results agree with previous determinations and contribute important information to an early assessment of detector performance.