Likely existence of bound states and the Efimov effect in the triple-$J/\psi$ system

Ya-Wen Pan, Zhi-Wei Liu, Li-Sheng Geng +2

The ground-breaking discovery of the first fully charmed tetraquark state $X(6900)$ in the $J/\psi J/\psi$ invariant mass distribution by the LHCb collaboration has inspired intensive the…