Very recently the LHCb Collaboration reported the discovery of two open charm tetraquark states, $X_{ 0}(2866)$ and $X_{ 1}(2904)$. In the present work, we study the $D^{ (\ast)}$ and $\bar{ K}^{ (\ast)}$ interaction in the one-boson exchange model and show that the $X_{ 0}(2866)$ can be understood as a $D^{ \ast}\bar{ K}^{ \ast}$ molecule with $I(J^{ P})=0(0^{ +})$, or at least it has a large molecular component. On the other hand, the $X_{ 1}(2904)$ can not be interpreted as a molecular state. Inspired by the discovery of the $X_0(2866)$ and the fact that the $D^*\bar{ K}^*$ interaction is strong enough to generate a bound state, we also discuss likely existence of other open charm molecules. In the meson-meson sector, two molecules near the mass thresholds of $DD^{ \ast}$ and $D^{ \ast}D^{ \ast}$ with $I(J^{ P})=0(1^{ +})$ are obtained, and using the heavy quark flavor symmetry their $\bar{ B}\bar{ B}^{ \ast}$ and $\bar{ B}^{ \ast}\bar{ B}^{ \ast}$ counterparts are also predicted. In the meson-baryon sector, 7 open charm molecules with $I=1/2$ near the mass thresholds of $D^{ (\ast)}\Sigma_{ c}^{ (\ast)}$ naturally appear, as dictated by the heavy quark spin symmetry.
Categories: hep-ph hep-ex