Observation of $\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and $\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$

Abstract

Using a sample of $1.3\times 10^9$ $J/\ddot{I}ˆ$ events collected with the BESIII detector, we report the first observation of $\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and $\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$. The measured branching fractions are $\mathcal{B}$($\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$) = $(8.53\pm 0.69(stat.)\pm 0.64(syst.))\times 10^{-5}$ and $\mathcal{B}$($\hat{I}{\cdot }^{\prime }\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0\ddot{I}{€}^0$) = $(1.82\pm 0.35(stat.)\pm 0.18(syst.))\times 10^{-4}$, which are consistent with theoretical predictions based on a combination of chiral perturbation theory and vector-meson dominance.

6 pages and 6 figures