Fully Charmed Tetraquark States in 8[cc̄]⊗8[cc̄] 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[cc̄]⊗8[cc̄] color configuration via QCD sum rules. By constructing nine 8[cc̄]⊗8[cc̄] type currents with quantum numbers JPC=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 JPC=1⁺⁻,2⁺⁺ lie around 6.48 ~ 6.62 GeV while the fully-charm tetraquark states with JPC=0⁻⁺,0⁻⁻,1⁻⁻,1⁻⁺ are about 6.85~7.02 GeV. Notably, the mass predictions for the cc̄cc̄ tetraquarks, specifically those with JPC=2⁺⁺, align with the broad structure identified by LHCb. Moreover, the masses of fully-charm tetraquarks with JPC=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[cc̄]⊗8[cc̄] components within the di-J/ψ structures observed by LHCb. The predictions for tetraquark states with JPC=0⁻⁻,1⁺⁻,1⁻⁻ may be accessible in the future BelleII, Super-B, PANDA, and LHCb experiments.