Search for the weak decay $\hat{I}{\cdot }^{\prime }\to K^{\pm }\ddot{I}{€}^{\mp }$ and precise measurement of the branching fraction $\mathcal{B}(J/\ddot{I}ˆ\to \ddot{I}•\hat{I}{\cdot }^{\prime })$

Abstract

We present the first search for the rare decay of $\hat{I}{\cdot }^{\prime }$ into $K^{\pm }\ddot{I}{€}^{\mp }$ in $J/\ddot{I}ˆ\to \ddot{I}•\hat{I}{\cdot }^{\prime }$, using a sample of $1.3\times 10^9$ $J/\ddot{I}ˆ$ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90\% confidence level for the ratio $\frac{\mathcal{B}(\hat{I}{\cdot }^{\prime }\to K^{\pm }\ddot{I}{€}^{\mp })}{\mathcal{B}(\hat{I}{\cdot }^{\prime }\to {\hat{I}}^3\ddot{I}{€}^{+}\ddot{I}{€}^{-})}$ is determined to be $1.3\times 10^{-4}$. In addition, we report the measurement of the branching fraction of $J/\ddot{I}ˆ\to \ddot{I}•\hat{I}{\cdot }^{\prime }$ to be $(5.10\pm 0.03(\text{stat.})\pm 0.32(\text{syst.}))\times 10^{-4}$, which agrees with previous results from BESII.