Measurement of the branching fraction of the $B^0\to K_S^0{\pi }^0\gamma$ decay using 190 fb${}^{-1}$ of Belle II data

We report the measurement of the branching fraction of the $B^0\to K_S^0{\pi }^0\gamma$ decay in $e^{+}{e}^{-}\to \mathrm{{\rm Y}}(4S)\to B\bar{B}$ data recorded by the Belle II experiment at the SuperKEKB asymmetric-energy collider and corresponding to 190 fb${}^{-1}$ of integrated luminosity. The signal yield is measured to be $121\pm 29\text{(stat.)}$, leading to the branching fraction $\mathcal{B}(B^0\to K_S^0{\pi }^0\gamma )=(7.3\pm 1.8\text{(stat.)}\pm 1.0\text{(syst.)})\times {10}^{-6}$, which agrees with the known value.