Interpretation of structure in the di-$J/\Psi$ spectrum

Structure in the di-$J/\Psi$ mass spectrum observed by the LHCb experiment around 6.9 and 7.2 GeV is interpreted in terms of $J^{PC}=0^{++}$ and $2^{++}$ resonances between a $cc$ diquark and a $\overline{c}\overline{c}$ antidiquark, using a recently confirmed string-junction picture to calculate tetraquark masses. The main peak around 6.9 GeV is likely dominated by the $0^{++}(2S)$ state, a radial excitation of the $cc-\overline{c}\overline{c}$ tetraquark, which we predict at $6.871±0.025$ $GeV$. The dip around 6.75 GeV is ascribed to the opening of the S-wave $di-χ_{c0}$ channel, while the dip around 7.2 GeV could be correlated with the opening of the di-$η_c(2S)$ or $\Xi_{cc}\overline\Xi_{cc}$ channel. The low-mass part of the di-$J/\Psi$ structure appears to require a broad resonance consistent with a predicted $2^{++}(1S)$ state with invariant mass around $M_{inv}=6400$ $MeV$. Implications for $bb\overline{b}\overline{b}$ tetraquarks are discussed.