We report measurements of the branching fraction and $CP$ asymmetry in $B^0\to {\pi }^0{\pi }^0$ decays reconstructed at Belle II in an electron-positron collision sample containing $198\times {10}^{6}B\overline{B}$ pairs. We measure a branching fraction $\mathcal{B}(B^0\to {\pi }^0{\pi }^0)=(1.38\pm 0.27\pm 0.22)\times {10}^{-6}$ and a $CP$ asymmetry ${\mathcal{A}}_{CP}(B^0\to {\pi }^0{\pi }^0)=-0.14\pm 0.46\pm 0.07$, where the first uncertainty is statistical and the second is systematic.

• Received 22 March 2023
• Accepted 9 May 2023
• Corrected 22 May 2024

DOI:https://doi.org/10.1103/PhysRevD.107.112009

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Published by the American Physical Society