The $X(6900)$ peak could be a molecular state

The analyses of the LHCb data on $X(6900)$ found in di-$J\mathrm{/}\psi$ and $J\mathrm{/}\psi \psi (3686)$ systems are performed using a momentum-dependent {Flatté}-like parameterization. The use of the pole counting rule and spectral density function sum rule give consistent conclusions that $X(6900)$ may not be a molecule of $J\mathrm{/}\psi \psi (3686)$. Nevertheless it is still possible that $X(6900)$ be a molecule of higher states, such as $J\mathrm{/}\psi \psi (3770)$, ${\chi }_{c0}{\chi }_{c2}$, etc.