We report results from the first search for the rare penguin-dominated decay mode $B^0\to K_S^0{K}_S^0\gamma$, which can result from the production of tensor mesons $f(1270)$ and $f^{\prime }(1525)$ in association with a photon. The search uses the full data sample of $772\times {10}^{6}B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. No statistically significant signals are observed in the $K_S^0{K}_S^0$ invariant mass range $1\mathrm{GeV}/c^2<M_{K_S^0{K}_S^0}<3\mathrm{GeV}/c^2$, and the following upper limits at the 90% confidence level are obtained: $\mathcal{B}(B^0\to K_S^0{K}_S^0\gamma )<5.8\times {10}^{-7}$, $\mathcal{B}(B^0\to f_2\gamma )\times \mathcal{B}(f_2(1270)\to K_S^0{K}_S^0)<3.1\times {10}^{-7}$, and $\mathcal{B}(B^0\to f_2^{\prime }\gamma )\times \mathcal{B}(f_2^{\prime }(1525)\to K_S^0{K}_S^0)<2.1\times {10}^{-7}$. In addition, 90% confidence-level upper limits in the range of $[0.7–2.9]\times {10}^{-7}$ are also obtained on the $B^0\to K_S^0{K}_S^0\gamma$ branching fraction in bins of $M_{K_S^0{K}_S^0}$.

• Received 11 March 2022
• Accepted 12 July 2022

DOI:https://doi.org/10.1103/PhysRevD.106.012006

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Published by the American Physical Society