Observation of the decay $\ddot{I}ˆ(3686)\to \hat{I}{\pounds }^0\bar{\hat{I}}{\pounds }^0\ddot{I}‰$

Abstract

Using a dataset of $(27.12\pm 0.14)\times 10^8$ $\ddot{I}ˆ(3686)$ events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of the decay $\ddot{I}ˆ(3686)\to \hat{I}{\pounds }^0\bar{\hat{I}}{\pounds }^0\ddot{I}‰$ with a statistical significance of 8.9$\ddot{I}ƒ$. The measured branching fraction is $(1.24\pm 0.16_{\text{stat}}\pm 0.11_{\text{sys}})\times 10^{-5}$, where the first uncertainty is statistical and the second is systematic. Additionally, we investigate potential intermediate states in the invariant mass distributions of $\hat{I}{\pounds }^0\ddot{I}‰$, $\bar{\hat{I}}{\pounds }^0\ddot{I}‰$ and $\hat{I}{\pounds }^0\bar{\hat{I}}{\pounds }^0$. A hint of a resonance is observed in the invariant mass distribution of $M_{\hat{I}{\pounds }^0(\bar{\hat{I}}{\pounds }^0)\ddot{I}‰}$, located around 2.06 GeV/$c^2$, with a significance of 2.5$\ddot{I}ƒ$.