Search for $\hat{I}{\cdot }_c(2S)\to K^{+}{K}^{-}\hat{I}{\cdot }^{\prime }$ decay

Abstract

Using $(2.712\pm 0.014)\times 10^9$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector operating at the BEPCII, we find an evidence of the $\hat{I}{\cdot }_c(2S)\to K^{+}{K}^{-}\hat{I}{\cdot }^{\prime }$ decay with a statistical significance of 3.1$\ddot{I}ƒ$. Its decay branching fraction is measured to be $(12.24\pm 4.60(stat.)\pm 2.37(syst.)\pm 4.68(extr.))\times 10^{-4}$, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is from the branching fraction of the $\ddot{I}ˆ(3686)\to {\hat{I}}^3\hat{I}{\cdot }_c(2S)$ decay. The upper limit on the product branching fraction $B[\ddot{I}ˆ(3686)\to {\hat{I}}^3\hat{I}{\cdot }_c(2S)]\times$ $B[\hat{I}{\cdot }_c(2S)\to K^{+}{K}^{-}\hat{I}{\cdot }^{\prime }]$ is set to be $1.14\times 10^{-6}$ at $90\%$ confidence level. In addition, the branching fractions of $\ddot{I}{‡}_{c1}\to K^{+}{K}^{-}\hat{I}{\cdot }^{\prime }$ and $\ddot{I}{‡}_{c2}\to K^{+}{K}^{-}\hat{I}{\cdot }^{\prime }$ are updated to be $(8.47\pm 0.09(stat.)\pm 0.47(syst.))\times 10^{-4}$ and $(1.53\pm 0.04(stat.)\pm 0.08(syst.))\times 10^{-4}$, respectively. The precision is improved by twofold.