The Hidden Charm Decay of $X(3872), Y(3940)$ and Final State Interaction   Effects
  We investigate whether the final state interaction (FSI) effect plays a significant role in the large hidden charm decay width of X(3872) and Y(3940) using a model. Our numerical result suggests (1) the FSI contribution to $X(3872)\to J/\psi\rho $ is tiny; (2) $\Gamma[ Y(3940)\to D\bar{D}^{*}+\text{h.c.}\to J/\psi\omega ]$ from FSI is around several keV, far less than Belle's experimental value 7 MeV. 
Xiang Liu, Bo Zhang and Shi-Lin Zhu