The $X_0(2900)$ and its heavy quark spin partners in molecular picture

Abstract

The $X_0(2900)$ observed by the LHCb Collaboration recently in the $D^{-}{K}^{+}$ invariant mass of the $B^{+}\to D^{+}{D}^{-}{K}^{+}$ process is the first exotic candidate with four different flavors, which opens a new era for the hadron community. Under the assumption that the $X_0(2900)$ is a $I(J^P)=0(0^{+})$ ${\bar{D}}^{\ast }{K}^{\ast }$ hadronic molecule, we extract the whole heavy-quark symmetry multiplet formed by the $\left(\bar{D},{\bar{D}}^{\ast }\right)$ doublet and the $K^{\ast }$ meson. For the bound state case, there would be two additional $I(J^P)=0(1^{+})$ hadronic molecules associated with the $\bar{D}{K}^{\ast }$ and ${\bar{D}}^{\ast }{K}^{\ast }$ channels as well as one additional $I(J^P)=0(2^{+})$ ${\bar{D}}^{\ast }{K}^{\ast }$ molecule. In the light quark limit, they are $36.66\mathrm{MeV}$ and $34.22\mathrm{MeV}$ below the $\bar{D}{K}^{\ast }$ and ${\bar{D}}^{\ast }{K}^{\ast }$ thresholds, respectively, which are unambiguously fixed by the mass position of the $X_0(2900)$. For the virtual state case, there would be one additional $I(J^P)=0(1^{+})$ hadronic molecule strongly coupling to the $\bar{D}{K}^{\ast }$ channel and one additional $I(J^P)=0(2^{+})$ ${\bar{D}}^{\ast }{K}^{\ast }$ molecule. Searching for these heavy quark spin partners will help shed light on the nature of the $X_0(2900)$.

Comments: published in Chinese Physics C