Precision measurement of the branching fraction of \boldmath $J/\psi \to K^{+}{K}^{-}$ via $\psi (2S)\to {\pi }^{+}{\pi }^{-}J/\psi$

Abstract

Using a sample of $448.1\times 10^6$ $\psi (2S)$ events collected with the BESIII detector, we perform a study of the decay $J/\psi \to K^{+}{K}^{-}$ via $\psi (2S)\to {\pi }^{+}{\pi }^{-}J/\psi$. The branching fraction of $J/\psi \to K^{+}{K}^{-}$ is determined to be ${\mathcal{B}}_{K^{+}{K}^{-}}=(3.072\pm 0.023(stat.)\pm 0.050(syst.))\times 10^{-4}$, which is consistent with previous measurements but with significantly improved precision.

to be submitted to PRD