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

TL;DR

This paper models the exotic $X_0(2900)$ as a hadronic molecule, predicts its heavy quark spin partners, and discusses their properties to understand the nature of this newly observed state.

Contribution

It introduces a molecular interpretation of $X_0(2900)$ and predicts its heavy quark spin partners, providing specific mass and quantum number details.

Findings

Predicted multiple heavy quark spin partner molecules with specific quantum numbers.

Mass differences of approximately 34-37 MeV below relevant thresholds.

Identification of potential bound and virtual state partners for $X_0(2900)$.

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 $I(J^P)=0(0^+)$ $\bar{D}^*K^*$ hadronic molecule, we extract the whole heavy-quark symmetry multiplet formed by the $\left(\bar{D},\bar{D}^*\right)$ doublet and the $K^*$ meson. For the bound state case, there would be two additional $I(J^P)=0(1^+)$ hadronic molecules associated with the $\bar{D}K^*$ and $\bar{D}^*K^*$ channels as well as one additional $I(J^P)=0(2^+)$ $\bar{D}^*K^*$ molecule. In the light quark limit, they are $36.66~\mathrm{MeV}$ and $34.22~\mathrm{MeV}$ below the $\bar{D}K^*$ and $\bar{D}^*K^*$ 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 $\bar{D}K^*$ channel and one additional $I(J^P)=0(2^+)$ $\bar{D}^*K^*$ molecule. Searching for these heavy quark spin partners will help shed light on the nature of the $X_0(2900)$.