We measure the time-dependent $CP$ violation parameters in $B^0\to K_S^0{K}_S^0{K}_S^0$ decays using $772\times {10}^{6}B\overline{B}$ pairs collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The obtained mixing-induced and direct $CP$ asymmetries are $-0.71\pm 0.23(\mathrm{stat})\pm 0.05(\mathrm{syst})$ and $0.12\pm 0.16(\mathrm{stat})\pm 0.05(\mathrm{syst})$, respectively. These values are consistent with the Standard Model predictions. The significance of $CP$ violation differs from zero by 2.5 standard deviations.

• Received 3 November 2020
• Accepted 15 January 2021

DOI:https://doi.org/10.1103/PhysRevD.103.032003

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Published by the American Physical Society