Observation of the electromagnetic doubly OZI-suppressed decay $J/\ddot{I}ˆ\to \ddot{I}•\ddot{I}{€}^0$

Abstract

Using a sample of $1.31$ billion $J/\ddot{I}ˆ$ events accumulated with the BESIII detector at the BEPCII collider, we report the observation of the decay $J/\ddot{I}ˆ\to \ddot{I}•\ddot{I}{€}^0$, which is the first evidence for a doubly Okubo-Zweig-Iizuka suppressed electromagnetic $J/\ddot{I}ˆ$ decay. A clear structure is observed in the $K^{+}{K}^{-}$ mass spectrum around 1.02 GeV/$c^2$, which can be attributed to interference between $J/\ddot{I}ˆ\to \ddot{I}•\ddot{I}{€}^0$ and $J/\ddot{I}ˆ\to K^{+}{K}^{-}\ddot{I}{€}^0$ decays. Due to this interference, two possible solutions are found. The corresponding measured values of the branching fraction of $J/\ddot{I}ˆ\to \ddot{I}•\ddot{I}{€}^0$ are $[2.94\pm 0.16\text{(stat.)}\pm 0.16\text{(syst.)}]\times 10^{-6}$ and $[1.24\pm 0.33\text{(stat.)}\pm 0.30\text{(syst.)}]\times 10^{-7}$.

7 pages, 4 figures, published in Phys. Rev. D