The BESIII collaboration recently reported the observation of two resonance structures in the processes e⁺e^-→ωχ_c1 and e⁺e^-→ωχ_c2. One structure is likely to be the well-established resonance ψ(4415), and another is observed for the first time. The results have been published in Physics Review Letters on April 19, 2024 [Phys. Rev. Lett. 132, 161901 (2024)].

 

 

In this work, the e⁺e^-→ωχ_c1,2 cross sections are measured at the center-of-mass energies from 4.308 to 4.951 GeV at the BESIII experiment. For each process, a nontrivial feature is observed in the cross section line shape. Under the assumption that one single resonance describes the corresponding shape, the mass and width for e⁺e^-→ωχ_c1 are determined to be M=(4544.2±18.7±1.7) MeV/c² and Γ=(116.1±33.5±1.7) MeV. This structure is observed for the first time with a significance of 5.8σ. The mass is significantly higher compared to the structures recently observed around 4.480 GeV/c² in e⁺e^-→K⁺K^-J/ψ and e⁺e^-→D^*0D^*-π⁺. It is yet unclear whether or not these two states are the same based on the currently available information, and further measurements with higher precision in this energy region will be necessary. For the e⁺e^-→ωχ_c2 process, the extracted parameters are M=(4413.6±9.0±0.8) MeV/c² and Γ=(110.5±15.0±2.9) MeV, suggesting that this is likely the well-known ψ(4415) and implying the existence of the hidden-charm decay ψ(4415)→ωχ_c2.

 

 

FIG. 1. Fits to the cross sections of e⁺e^-→ωχ_c1 (left) and e⁺e^-→ωχ_c2 (right), two structures are observed.