Insights into the nature of the $P_{cs}(4459)$

Abstract: We study the nature of the recently observed $P_{cs}(4459)$ by the LHCb collaboration by employing three methods based on the elastic effective-range expansion and the resulting size of the effective-range, the saturation of the compositeness relation and width of the resonance, and a direct fit to data involving the channels $J/\psi\Lambda$, $\Xi'c\bar{D}$ and $\Xi_c\bar{D}^*$. We have also considered the addition of a CDD pole but this scenario can be discarded. Our different analyses clearly indicate the molecular nature of the $P{cs}(4459)$ with a clear $\Xi_c\bar{D}^*$ dominant component. In relation with heavy-quark-spin symmetry our results also favor the actual existence of two resonances with $J=1/2$ (the lighter one) and $3/2$ (the heavier one) in the energy region of the $P_{cs}(4459)$. In the scenario of two-resonance for the $P_{cs}(4459)$, the inclusion of the $\Xi_c'\bar{D}$ channel is required for the their mass splitting and it allows one to determine the spin structures of the two resonances.