Search for the rare decay ${\eta }^{\prime }\to 3\gamma$

Abstract

Using a data sample of $(10087\pm 44)\times 10^{6}J/\psi$ events collected with the BESIII detector, we search for the rare decay ${\eta }^{\prime }\to 3\gamma$ via the process $J/\psi \to \gamma {\eta }^{\prime }$. No significant signal is observed and an upper limit on the branching fraction of ${\eta }^{\prime }\to 3\gamma$ is set at $\mathcal{B}({\eta }^{\prime }\to 3\gamma )<2.25\times 10^{-5}$ at the 90\% confidence level. This result improves the previous upper limit by more than a factor of four.