Five-flavor $udsc\bar{b}$ molecular pentaquarks from heavy-quark and local hidden gauge symmetries

Abstract

We study a family of genuinely exotic five-flavor molecular pentaquark states containing the five quark flavors $u,d,s,c,b$ that form experimentally accessible hadrons. We construct the meson-baryon interaction from the local hidden gauge symmetry combined with heavy-quark spin symmetry, following the chiral unitary description that reproduces the LHCb hidden-charm strange pentaquarks. Heavy-quark flavor symmetry allows us to obtain the $udsc\bar{b}$ sector by replacing the anti-charm quark in the meson with an anti-bottom quark while keeping the charm quark in the baryon. As a result, we obtain ten threshold-associated isoscalar poles with $J^P=1/2^-,3/2^-,5/2^-$ in the range $7.72$ to $7.96$ GeV. They are narrow and organized into heavy-quark spin multiplets with predicted near-degeneracies. There are four states that overlap with the earlier two-sector study in the literature to about $2$ MeV, which shows that the separate-sector treatment is recovered as a limit of this work. Moreover, we also identify two additional, more deeply bound $B_s\Lambda_c$ and $B_s^{*}\Lambda_c$ poles generated by strong inter-channel coupling because these poles are farther from their dominated thresholds. This is an interesting signal that can be searched for at LHCb in the $B_c\Lambda$ and $B_s^{*}\Lambda_c$ invariant mass spectra.