Molecular states of heavy quark mesons

We explore molecular states of two open heavy-quark mesons $\left(Q\overline{q}\right)-\left(q\overline{Q}\right)$ in a quark-based model in terms of a four-body nonrelativistic Hamiltonian with pairwise effective interactions. Molecular states are found in the combinations of $\left\{D,D^{*},B,B^{*}\right\}$ with $\left\{\overline{D},{\overline{D}}^{*},\overline{B},{\overline{B}}^{*}\right\}$, including a weakly bound $D{\overline{D}}^{*}$ state near the threshold which may be qualitatively identified as the 3872 state observed recently by the Belle Collaboration.