Search for the rare decay $\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^0\ddot{I}{€}^0\ddot{I}{€}^0\ddot{I}{€}^0$ at BESIII

Abstract

Based on a sample of 1.31 billion $J/\ddot{I}ˆ$ events collected with the BESIII detector, we perform a search for the rare decay $\hat{I}{\cdot }^{\prime }\to 4\ddot{I}{€}^0$ via $J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }^{\prime }$. No significant $\hat{I}{\cdot }^{\prime }$ signal is observed in the invariant mass spectrum of 4$\ddot{I}{€}^0$. With a Bayesian approach, the upper limit on the branching fraction of $\hat{I}{\cdot }^{\prime }\to 4\ddot{I}{€}^0$ is determined to be $\mathcal{B}(\hat{I}{\cdot }^{\prime }\to 4\ddot{I}{€}^0)$ $<4.94\times 10^{-5}$ at the 90\% confidence level, which is a factor of six smaller than the previous experimental limit.