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

TL;DR

This paper reports a highly precise measurement of the branching fraction for the decay $J/rac{K^+K^-}$ using a large sample of $rac{448.1 imes 10^6}{ ext{events}}$ from $rac{ ext{psi}(2S)}{ ext{decay}}$, confirming previous results with better accuracy.

Contribution

The study provides the most precise measurement to date of the $J/rac{K^+K^-}$ branching fraction via $rac{ ext{psi}(2S)}{ ext{decay}}$, improving the accuracy of previous measurements.

Findings

Branching fraction measured as (3.072 ± 0.023 (stat) ± 0.050 (syst)) × 10^{-4}

Results are consistent with previous measurements

Significantly improved precision over prior studies

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 $J/\psi\rightarrow K^+K^-$ via $\psi(2S)\rightarrow \pi^+\pi^-J/\psi$. The branching fraction of $J/\psi\rightarrow K^+K^-$ is determined to be $\mathcal{B}_{K^+K^-}=(3.072\pm 0.023({\rm stat.})\pm 0.050({\rm syst.}))\times 10^{-4}$, which is consistent with previous measurements but with significantly improved precision.