Observation of $\hat{I}{\cdot }_c\to p\bar{p}\hat{I}\cdot$ via $\ddot{I}ˆ(3686)\to {\hat{I}}^{3}p\bar{p}\hat{I}\cdot$

Abstract

The decay $\hat{I}{\cdot }_c\to p\bar{p}\hat{I}\cdot$ is observed for the first time with a significance of exceeding $10\ddot{I}ƒ$. It is found by analyzing $(2712.4\pm 14.3)\times 10^6$ $\ddot{I}ˆ(3686)$ events accumulated at the BESIII detector. The measured branching fraction of $\hat{I}{\cdot }_c\to p\bar{p}\hat{I}\cdot$ via $\ddot{I}ˆ(3686)\to {\hat{I}}^{3}p\bar{p}\hat{I}\cdot$ is significantly influenced by the interference between the resonant $\hat{I}{\cdot }_c$ decay and the non-resonant process $\ddot{I}ˆ(3686)\to {\hat{I}}^{3}p\bar{p}\hat{I}\cdot$ and is measured in both constructive- and destructive-interference scenarios. The joint branching fraction of $\ddot{I}ˆ(3686)\to {\hat{I}}^3\hat{I}{\cdot }_c$, $\hat{I}{\cdot }_c\to p\bar{p}\hat{I}\cdot$ is measured to be $(3.2\pm 0.1\pm 0.9)\times 10^{-6}$ or $(8.7\pm 0.3\pm 2.1)\times 10^{-6}$ for constructive- or destructive-interference solutions, respectively, where the first uncertainties are statistical and the second systematic. The branching fraction of $\hat{I}{\cdot }_c\to p\bar{p}\hat{I}\cdot$ is determined to be $\mathcal{B}(\hat{I}{\cdot }_c\to p\bar{p}\hat{I}\cdot )=(0.90\pm 0.04\pm 0.21\pm 0.13)\times 10^{-3}$ or $(2.42\pm 0.07\pm 0.48\pm 0.34)\times 10^{-3}$ for the two solutions, respectively, where the third uncertainties are due to the uncertainty in the branching fraction of $\ddot{I}ˆ(3686)\to {\hat{I}}^3\hat{I}{\cdot }_c$.

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