Observation of $\ddot{I}ˆ(3686)\to e^{+}{e}^{-}\ddot{I}{‡}_{cJ}$ and $\ddot{I}{‡}_{cJ}\to e^{+}{e}^{-}J/\ddot{I}ˆ$

Abstract

Using $4.479\times 10^8$ $\ddot{I}ˆ(3686)$ events collected with the BESIII detector, we search for the decays $\ddot{I}ˆ(3686)\to e^{+}{e}^{-}\ddot{I}{‡}_{c0,1,2}$ and $\ddot{I}{‡}_{c0,1,2}\to e^{+}{e}^{-}J/\ddot{I}ˆ$. The decays $\ddot{I}ˆ(3686)\to e^{+}{e}^{-}\ddot{I}{‡}_{c0,1,2}$ and $\ddot{I}{‡}_{c0,1,2}\to e^{+}{e}^{-}J/\ddot{I}ˆ$ are observed for the first time. The measured branching fractions are $\mathcal{B}(\ddot{I}ˆ(3686)\to e^{+}{e}^{-}\ddot{I}{‡}_{c0,1,2})=(11.7\pm 2.5\pm 1.0)\times 10^{-4}$, $(8.6\pm 0.3\pm 0.6)\times 10^{-4}$, $(6.9\pm 0.5\pm 0.6)\times 10^{-4}$, and $\mathcal{B}(\ddot{I}{‡}_{c0,1,2}\to e^{+}{e}^{-}J/\ddot{I}ˆ)=(1.51\pm 0.30\pm 0.13)\times 10^{-4}$, $(3.73\pm 0.09\pm 0.25)\times 10^{-3}$, $(2.48\pm 0.08\pm 0.16)\times 10^{-3}$. The ratios of the branching fractions $\frac{\mathcal{B}(\ddot{I}ˆ(3686)\to e^{+}{e}^{-}\ddot{I}{‡}_{c0,1,2})}{\mathcal{B}(\ddot{I}ˆ(3686)\to {\hat{I}}^3\ddot{I}{‡}_{c0,1,2})}$ and $\frac{\mathcal{B}(\ddot{I}{‡}_{c0,1,2}\to e^{+}{e}^{-}J/\ddot{I}ˆ)}{\mathcal{B}(\ddot{I}{‡}_{c0,1,2}\to {\hat{I}}^{3}J/\ddot{I}ˆ)}$ are also reported.