Fully Charmed Tetraquark States in 8_[cc̅]⊗8_[cc̅] Color Structure via QCD Sum Rules

Stimulated by the recent experimental results on the fully-charm tetraquark states, we systematically calculate the mass spectra of the fully-charm tetraquark states in 8_[cc̅]⊗8_[cc̅] color configuration via QCD sum rules. By constructing nine 8_[cc̅]⊗8_[cc̅] type currents with quantum numbers J^PC=0^-+,0^–,1^-+,1^+-,1^– and 2^++, we perform analytic calculation up to dimension six in the Operator Product Expansion (OPE). We find the fully-charm tetraquark states with J^PC=1^+-,2^++ lie around 6.48 ∼ 6.62 GeV while the fully-charm tetraquark states with J^PC=0^-+,0^–,1^–,1^-+ are about 6.85∼7.02 GeV. Notably, the mass predictions for the cc̅cc̅ tetraquarks, specifically those with J^PC=2^++, align with the broad structure identified by LHCb. Moreover, the masses of fully-charm tetraquarks with J^PC=0^-+ and 1^-+ are anticipated to match closely with the mass of X(6900), considering the margin of error. Such findings hint at the presence of some 8_[cc̅]⊗8_[cc̅] components within the di-J/ψ structures observed by LHCb. The predictions for tetraquark states with J^PC=0^–,1^+-,1^– may be accessible in the future BelleII, Super-B, PANDA, and LHCb experiments.