Study of $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(3686)\to \hat{I}\pounds (1385{)}^0\bar{\hat{I}}\pounds (1385{)}^0$ and $\hat{I}{ž}^0\bar{\hat{I}}{ž}^0$

Abstract

We study the decays of $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(3686)$ to the final states $\hat{I}\pounds (1385{)}^0\bar{\hat{I}}\pounds (1385{)}^0$ and $\hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ based on a single baryon tag method using data samples of $(1310.6\pm 7.0)\times 10^6$ $J/\ddot{I}ˆ$ and $(447.9\pm 2.9)\times 10^6$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector at the BEPCII collider. The decays to $\hat{I}\pounds (1385{)}^0\bar{\hat{I}}\pounds (1385{)}^0$ are observed for the first time. The measured branching fractions of $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(3686)\to \hat{I}{ž}^0\bar{\hat{I}}{ž}^0$ are in good agreement with, and much more precise, than the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for $J/\ddot{I}ˆ\to \hat{I}\pounds (1385{)}^0\bar{\hat{I}}\pounds (1385{)}^0$, $\hat{I}\pm =-0.64\pm 0.03\pm 0.10$, is found to be negative, different to the other decay processes in this measurement. In addition, the "12\% rule" and isospin symmetry in the $J/\ddot{I}ˆ$ and $\ddot{I}ˆ(3686)\to \hat{I}ž\bar{\hat{I}}ž$ and $\hat{I}\pounds (1385)\bar{\hat{I}}\pounds (1385)$ systems are tested.

11 pages, 7 figures. This version is consistent with paper published in Phys.Lett. B770 (2017) 217-225