Observation of e+e-→K+K-J/ψ via initial-state radiation at Belle

The process e+e-→K+K-J/ψ is observed for the first time via initial-state radiation. The cross section of e+e-→K+K-J/ψ for center-of-mass energies between threshold and 6.0 GeV is measured using 673fb-1 of data collected with the Belle detector on and off the Υ(4S) resonance. No significant signal for Y(4260)→K+K-J/ψ is observed, and we determine B(Y(4260)→K+K-J/ψ)Γ(Y(4260)→e+e-)