Observation of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}J/\ensuremath{\psi}$ via initial-state radiation at Belle

Rapid Communication

Observation of $e^{+} e^{-} \to K^{+} K^{-} J / ψ$ via initial-state radiation at Belle

C. Z. Yuan et al. (Belle Collaboration)

Phys. Rev. D 77, 011105(R) – Published 16 January 2008

Abstract

The process $e^{+} e^{-} \to K^{+} K^{-} J / ψ$ is observed for the first time via initial-state radiation. The cross section of $e^{+} e^{-} \to K^{+} K^{-} J / ψ$ for center-of-mass energies between threshold and 6.0 GeV is measured using $673 {fb}^{- 1}$ of data collected with the Belle detector on and off the $Υ (4 S)$ resonance. No significant signal for $Y (4260) \to K^{+} K^{-} J / ψ$ is observed, and we determine $B (Y (4260) \to K^{+} K^{-} J / ψ) Γ (Y (4260) \to e^{+} e^{-}) < 1.2 eV / c^{2}$ at a 90% confidence level. We also find evidence for $e^{+} e^{-} \to K_{S}^{0} K_{S}^{0} J / ψ$ in the same data sample.