We study the dependence on the quark mass of the compositeness of the lowest-lying odd parity hyperon states. Thus, we pay attention to $\mathrm{\Lambda }$-like states in the strange, charm, and beauty sectors which are dynamically generated using a unitarized meson-baryon model. In the strange sector we use a SU(6) extension of the Weinberg-Tomozawa meson-baryon interaction, and we further implement the heavy-quark spin symmetry to construct the meson-baryon interaction when charmed or beauty hadrons are involved. In the three examined flavor sectors, we obtain two $J^P=1/2^{-}$ and one $J^P=3/2^{-}$ $\mathrm{\Lambda }$ states. We find that the $\mathrm{\Lambda }$ states which are bound states (the three ${\mathrm{\Lambda }}_b$) or narrow resonances [one $\mathrm{\Lambda }(1405)$ and one ${\mathrm{\Lambda }}_c(2595)$] are well described as molecular states composed of $s$-wave meson-baryon pairs. The ${\frac{1}{2}}^{-}$ wide $\mathrm{\Lambda }(1405)$ and ${\mathrm{\Lambda }}_c(2595)$ as well as the ${\frac{3}{2}}^{-}$ $\mathrm{\Lambda }(1520)$ and ${\mathrm{\Lambda }}_c(2625)$ states display smaller compositeness so they would require new mechanisms, such as $d$-wave interactions.

• Received 16 June 2015

DOI:https://doi.org/10.1103/PhysRevD.92.034011