Observation of $\hat{I}{\cdot }_c(1S)\to \hat{I}{\pounds }^0\bar{\hat{I}}{\pounds }^0$ and search for $h_c(1P)\to \hat{I}{\pounds }^0\bar{\hat{I}}{\pounds }^0$ via $\ddot{I}ˆ(3686)$ transitions

Abstract

Using $(2712.4\pm 14.3)\times 10^6\ddot{I}ˆ(3686)$ events collected by the BESIII detector operating at the BEPCII collider, the hadronic decay $\hat{I}{\cdot }_c\to \hat{I}{\pounds }^0\overline{\hat{I}{\pounds }^0}$ is observed for the first time via the radiative transition from $\ddot{I}ˆ(3686)$. It is found that the branching fraction has a significant dependence on the interference pattern between $\hat{I}{\cdot }_c(1S)$ and non-$\hat{I}{\cdot }_c(1S)$ processes. They are determined to be $\mathcal{B}(\hat{I}{\cdot }_c(1S)\to \hat{I}{\pounds }^0\overline{\hat{I}{\pounds }^0})=(2.59\pm 0.14(stat)\pm 0.44(syst))\times 10^{-3}$ and $(1.18\pm 0.12(stat)\pm 0.21(syst))\times 10^{-3}$, for the destructive and constructive interference scenarios, respectively. No significant signal is observed for the decay $h_c\to \hat{I}{\pounds }^0\overline{\hat{I}{\pounds }^0}$ in the hadronic transition $\ddot{I}ˆ(3686)\to \ddot{I}{€}^0{h}_c$, and an upper limit on its branching fraction is set to be $1.02\times 10^{-4}$ at the 90\% confidence level.