Precision measurement of the branching fraction of J/ψ→ K⁺K⁻ via ψ(2S)→ π⁺π⁻J/ψ

Using a sample of 448.1 × 10⁶ ψ(2S) events collected with the BESIII detector, we perform a study of the decay J/ψ→ K⁺K⁻ via ψ(2S)→ π⁺π⁻J/ψ. The branching fraction of J/ψ→ K⁺K⁻ is determined to be BK⁺K⁻=(3.072± 0.023( stat.)± 0.050( syst.))× 10⁻⁴, which is consistent with previous measurements but with significantly improved precision.