Branching fraction measurement of $J/\psi \rightarrow K_S K_L$ and search for $J/\psi \rightarrow K_S K_S$

TL;DR

This study precisely measures the branching fraction of $J/ ightarrow K_S K_L$ decays and sets a new, much stricter upper limit for the $J/ ightarrow K_S K_S$ process, testing fundamental symmetry expectations.

Contribution

It provides the most accurate measurement of $J/ ightarrow K_S K_L$ and significantly improves the upper limit for $J/ ightarrow K_S K_S$, advancing understanding of $J/$ decays.

Findings

Branching fraction of $J/ ightarrow K_S K_L$ measured as (1.93 ± 0.01 (stat.) ± 0.05 (syst.))×10^{-4}.

No signal observed for $J/ ightarrow K_S K_S$, upper limit set at 1.4×10^{-8}.

Results improve previous measurements and test EPR expectations.

Abstract

Using a sample of $1.31 \times 10^{9}$ $J/\psi$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/\psi \rightarrow K_S K_L$ and $K_S K_S$. The branching fraction of$J/\psi\rightarrow K_S K_L$ is determined to be ${\cal B}(J/\psi \rightarrow K_S K_L)=(1.93\pm0.01~(\rm{stat.})\pm0.05~(\rm{syst.}))\times10^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/\psi \rightarrow K_S K_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be ${\cal B}(J/\psi \rightarrow K_S K_S)<1.4\times10^{-8}$, which improves on the previous searches by two orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.