Evidence for the decay ψ (3770 )→K+K-

Existing data on the e⁺e^-→K⁺K^- cross section at the center-of-mass energy above 2.6 GeV are fitted with a sum of ψ (3770 ) resonant and continuum contributions. Two solutions for the resonance production cross section are found with a significance of 3.2 σ . Data on the e⁺e^-→K_SK_L cross section are used to resolve the ambiguity and to further constrain the values of the e⁺e^-→ψ (3770 )→K⁺K^- cross section and the interference phase. They are found to be σ_{ψ (3770 )}=0.07 3_-0.044^+0.061 pb and ϕ =(30 9_-35⁺¹⁷)^° , respectively. The same fitting procedure for the ψ (4160 ) resonance leads to the upper limit on the e⁺e^-→ψ (4160 )→K⁺K^- cross section σ_{ψ (4160 )}<0.062 pb at the 90% confidence level.