Determination of the mixing angle between new charmonium states
  Using the pictures for $X(3872)$ as a mixture of charmonium and molecular $D^{\ast 0}D^0$ states; $Y(3940)$ as a mixture of $\chi_{c0}$ and $D^\ast D^{\prime\ast}$ states, and $Y(4260)$ as a mixture of the tetra-quark state with charmonium states, the corresponding mixing angles are estimated within the QCD sum rules. We obtain that our predictions for the mixing angles of the $X(3872)$, $Y(4260)$ and $Y(3940)$ states are considerably smaller compared to works in which mixing angles are estimated from the condition in reproducing the the mass of these states. Our conclusion is that the considered pictures for the $X(3872)$, $Y(4260)$ and $Y(3940)$ states are not successful in describing these states. 
T. M. Aliev, M. Savci
hep-ph