Observation of the charmonium decay $\hat{I}{\cdot }_c\to {\hat{I}}^3{\hat{I}}^3$ in $J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }_c$

Abstract

Using $(2712.4\pm 14.3)\times 10^6$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector at the BEPCII collider, the decay $\hat{I}{\cdot }_c\to {\hat{I}}^3{\hat{I}}^3$ in $J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }_c$ is observed. We determine the product branching fraction $\mathcal{B}(J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }_c)\times \mathcal{B}(\hat{I}{\cdot }_c\to {\hat{I}}^3{\hat{I}}^3)=(5.23\pm 0.26_{stat.}\pm 0.30_{syst.})\times 10^{-6}$. This result is consistent with the LQCD calculation $(5.34\pm 0.16)\times 10^{-6}$ from HPQCD in 2023. By using the world-average values of $\mathcal{B}(J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }_c)$ and the total decay width of $\hat{I}{\cdot }_c$, the partial decay width $\hat{I}“(\hat{I}{\cdot }_c\to {\hat{I}}^3{\hat{I}}^3)$ is determined to be $(11.30\pm 0.56_{stat.}\pm 0.66_{syst.}\pm 1.14_{ref.})\mathrm{keV}$, which deviates from the corresponding world-average value by $3.4\ddot{I}ƒ$.

10 pages, 4 figures