We report the first reconstruction of the $B^{ 0} \to \pi^{ 0} \pi^{ 0}$ decay mode at Belle II using samples of 2019 and 2020 data that correspond to 62.8 fb$^{ -1}$ of integrated luminosity. We find $14.0^{ +6.8}_{ -5.6}$ signal decays, corresponding to a significance of 3.4 standard deviations and determine a branching ratio of $\mathcal{ B}(B^{ 0} \rightarrow \pi^{ 0} \pi^{ 0}) = [0.98^{ +0.48}_{ -0.39} \pm 0.27] \times 10^{ -6}$. The results agree with previous determinations and contribute important information to an early assessment of detector performance and Belle II's potential for future determinations of $\alpha/\phi_2$ using $B \rightarrow \pi \pi$ modes.
Categories: hep-ex