Di-${J/\psi}$ structures from the quark Pauli-blocking effect

The double-charmonium scattering states such as ${J/\psi}{J/\psi}$, $\eta_c{J/\psi}$, and $\eta_c\eta_c$ are investigated by a simplified quark cluster model. It is found that the quark Pauli-principle over the $c\bar c c\bar c$ system causes a rapid increase and a node in the two-meson phase shifts. The increase is not large enough to be regarded as a resonance, but if it is seen experimentally, that is most likely the quark Pauli-blocking effect.