Possible $D\bar{D}$ and $B\bar{B}$ Molecular states in a chiral quark   model
  We perform a systematic study of the bound state problem of $D\bar{D}$ and $B\bar{B}$ systems by using effective interaction in our chiral quark model. Our results show that both the interactions of $D\bar{D}$ and $B\bar{B}$ states are attractive, which consequently result in $I^G(J^{PC})=0^+(0^{++})$ $D\bar{D}$ and $B\bar{B}$ bound states. 
M. T. Li, W. L. Wang, Y. B. Dong and Z. Y. Zhang
nucl-th hep-ph