Observation of the Y(4230) and a new structure in e+e- → K+ K- J/ψ

The cross sections of e(+)e(-) -> K+K- J/psi at center-of-mass energies from 4.127 to 4.600 GeV are measured based on 15.6 fb(-1) data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in the line shape of the cross sections. The mass and width of the first structure are measured to be (4225.3 +/- 2.3 +/- 21.5) MeV and (72.9 +/- 6.1 +/- 30.8) MeV, respectively. They are consistent with those of the established Y(4230). The second structure is observed for the first time with a statistical significance greater than 8 sigma, denoted as Y(4500). Its mass and width are determined to be (4484.7 +/- 13.3 +/- 24.1) MeV and (111.1 +/- 30.1 +/- 15.2) MeV, respectively. The first presented uncertainties are statistical and the second ones are systematic. The product of the electronic partial width with the decay branching fraction Gamma(Y(4230) -> e(+)e(-))B(Y(4230) -> K+ K- J/psi) is reported.

Automated summary

In this study, the cross sections of e(+)e(-) -> K+K- J/psi at center-of-mass energies from 4.127 to 4.600 GeV were measured using the BESIII detector. Two resonant structures were observed, with one identified as Y(4230) and the other named Y(4500) and observed for the first time.