Branching fraction measurement of $J/\ddot{I}ˆ\to K_S{K}_L$ and search for $J/\ddot{I}ˆ\to K_S{K}_S$

Abstract

Using a sample of $1.31\times 10^9$ $J/\ddot{I}ˆ$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/\ddot{I}ˆ\to K_S{K}_L$ and $K_S{K}_S$. The branching fraction of$J/\ddot{I}ˆ\to K_S{K}_L$ is determined to be $\mathcal{B}(J/\ddot{I}ˆ\to K_S{K}_L)=(1.93\pm 0.01(stat.)\pm 0.05(syst.))\times 10^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/\ddot{I}ˆ\to K_S{K}_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be $\mathcal{B}(J/\ddot{I}ˆ\to K_S{K}_S)<1.4\times 10^{-8}$, which improves on the previous searches by two orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

7 pages, 4 figures. Minor revisions, matched to the version in Physical Review D