Using data samples with an integrated luminosity of $5.85{\mathrm{fb}}^{-1}$ collected at center-of-mass energies from 4.61 to 4.95 GeV with the BESIII detector operating at the BEPCII storage ring, we measure the cross section for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$. A new resonance with a mass of $M=4708_{-15}^{+17}\pm 21\mathrm{MeV}/c^2$ and a width of $\mathrm{\Gamma }=126_{-23}^{+27}\pm 30\mathrm{MeV}$ is observed in the energy-dependent line shape of the $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\psi$ cross section with a significance over $5\sigma$. The $K^{+}J/\psi$ system is also investigated to search for charged charmoniumlike states, but no significant $Z_{cs}^{+}$ states are observed. Upper limits on the Born cross sections for $e^{+}{e}^{-}\to K^{-}{Z}_{cs}(3985{)}^{+}/K^{-}{Z}_{cs}(4000{)}^{+}+c.c.$ with $Z_{cs}(3985{)}^{\pm }/Z_{cs}(4000{)}^{\pm }\to K^{\pm }J/\psi$ are reported at 90% confidence levels. The ratio of branching fractions $\{[\mathcal{B}(Z_{cs}(3985{)}^{+}\to K^{+}J/\psi )]/\mathcal{B}[Z_{cs}(3985{)}^{+}\to ({\overline{D}}^0{D}_s^{*+}+{\overline{D}}^{*0}{D}_s^{+})]\}$ is measured to be less than 0.03 at 90% confidence level.

• Received 31 August 2023
• Accepted 30 October 2023

DOI:https://doi.org/10.1103/PhysRevLett.131.211902

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Published by the American Physical Society