Speaker
Description
The BESIII experiment, with its unique data samples in the √s = 4.0 – 4.95 GeV region, continues to provide inputs for understanding charmonium and exotic XYZ states. This talk presents three recent analyses of processes with hidden charm in the final state. We report the search for a charmonium-like state ψ₀(4360) J^{PC} = 0^{--} via e⁺e⁻ → ηψ₀(4360) → ηηψ(2S), conducted at the center-of-mass energies of 4.84, 4.92, and 4.95 GeV. The upper limits are provided since no significant signal has been observed. Furthermore, we present a search for the process e⁺e⁻ → ηηJ/ψ at the center-of-mass energies from 4.226 to 4.950 GeV, with two different methods, exclusively and semi-inclusively. The upper limits for the reaction channel e+e− → ηηJ/ψ also serve as limits for the existence of a possible isospin partner to the charmonium-like isospin triplet Zc(3900) which decays to J/ψη. Finally, we disclose a precision measurement of the Born cross section for e⁺e⁻ → π⁰π⁰ψ(3686) across the energy range from 4.008 to 4.951 GeV. The obtained cross sections are found to be approximately one-half of those of e+e− → π+π−ψ(3686), and a coherent fit to the dressed cross sections is performed with the vector resonances Y(4230), Y(4390), and Y(4660).
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