Measurement of $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\hat{I}\cdot$ and $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\ddot{I}{€}^0$ decays

Abstract

Based on a sample of $448.1\times 10^6\ddot{I}ˆ(3686)$ events collected with the BESIII detector, a study of $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\ddot{I}{€}^0$ and $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\hat{I}\cdot$ is performed. Evidence of the isospin-violating decay $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\ddot{I}{€}^0$ is found for the first time with a statistical significance of $3.7\ddot{I}ƒ$, the branching fraction $\mathcal{B}(\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\ddot{I}{€}^0)$ is measured to be $(1.42\pm 0.39\pm 0.59)\times 10^{-6}$, and its corresponding upper limit is determined to be $2.47\times 10^{-6}$ at 90\% confidence level. A partial wave analysis of $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\hat{I}\cdot$ shows that the peak around $\hat{I}›\hat{I}\cdot$ invariant mass threshold favors a $\hat{I}{›}^{\ast }$ resonance with mass and width in agreement with the $\hat{I}›(1670)$. The branching fraction of the $\ddot{I}ˆ(3686)\to \hat{I}›\bar{\hat{I}}›\hat{I}\cdot$ is measured to be $(2.34\pm 0.18\pm 0.52)\times 10^{-5}$. The first uncertainties are statistical and the second are systematic.

11 pages, 7 figures, consistent with paper published in Phys. Rev. D 106, 072006 (2022)