Observation of the $Y(4230)$ and evidence for a new vector charmonium-like state $Y(4710)$ in $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\ddot{I}ˆ$

Abstract

Cross sections for the process $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\ddot{I}ˆ$ at center-of-mass energies from $4.128$ to $4.950$ GeV are measured using data samples with a total integrated luminosity of 21.2 fb${}^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring. The $Y(4230)$ state is observed in the energy dependence of the $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\ddot{I}ˆ$ cross section for the first time with a statistical significance of 26.0$\ddot{I}ƒ$. In addition, an enhancement around $4.710$ GeV, called the $Y(4710)$, is seen with a statistical significance of 4.2$\ddot{I}ƒ$. There is no clear structure around $4.484$ GeV. Using a fit with a coherent sum of three Breit-Wigner functions, we determine the mass and width of the $Y(4230)$ state to be $4226.9\pm 6.6\pm 21.9$ MeV/$c^2$ and $71.7\pm 16.2\pm 31.4$ MeV, respectively, and the mass and width of the $Y(4710)$ state to be $4704.0\pm 52.3\pm 69.5$ MeV/$c^2$ and $183.2\pm 114.0\pm 90.8$ MeV, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the average Born cross section ratio of $e^{+}{e}^{-}\to K_S^0{K}_S^{0}J/\ddot{I}ˆ$ to $e^{+}{e}^{-}\to K^{+}{K}^{-}J/\ddot{I}ˆ$ is measured to be $0.388_{-0.028}^{+0.035}\pm 0.016$, or $0.426_{-0.031}^{+0.038}\pm 0.018$ if three-body phase space is considered.

Update draft based the comments from PRD referee