Observation of $\ddot{I}ˆ(3686)\to p\bar{p}\hat{I}{\cdot }^{\prime }$ and improved measurement of $J/\ddot{I}ˆ\to p\bar{p}\hat{I}{\cdot }^{\prime }$

Abstract

We observe the process $\ddot{I}ˆ(3686)\to p\bar{p}\hat{I}{\cdot }^{\prime }$ for the first time, with a statistical significance higher than 10$\ddot{I}ƒ$, and measure the branching fraction of $J/\ddot{I}ˆ\to p\bar{p}\hat{I}{\cdot }^{\prime }$ with an improved accuracy compared to earlier studies. The measurements are based on $4.48\times 10^8$ $\ddot{I}ˆ(3686)$ and $1.31\times 10^9$ $J/\ddot{I}ˆ$ events collected by the BESIII detector operating at the BEPCII. The branching fractions are determined to be $B(\ddot{I}ˆ(3686)\to p\bar{p}\hat{I}{\cdot }^{\prime })=(1.10\pm 0.10\pm 0.08)\times 10^{-5}$ and $B(J/\ddot{I}ˆ\to p\bar{p}\hat{I}{\cdot }^{\prime })=(1.26\pm 0.02\pm 0.07)\times 10^{-4}$, where the first uncertainties are statistical and the second ones systematic. Additionally, the $\hat{I}\cdot -\hat{I}{\cdot }^{\prime }$ mixing angle is determined to be $-24^{\circ }\pm 11^{\circ }$ based on $\ddot{I}ˆ(3686)\to p\bar{p}\hat{I}{\cdot }^{\prime }$, and $-24^{\circ }\pm 9^{\circ }$ based on $J/\ddot{I}ˆ\to p\bar{p}\hat{I}{\cdot }^{\prime }$, respectively.

9 pages, 20 figures