Hidden-charm pentaquarks and their hidden-bottom and Bc -like partner states

Abstract

In the framework of the color-magnetic interaction, we have systematically studied the mass splittings of the possible hidden-charm pentaquarks $qqqc\overline{c}$ ($q=u$, $d$, $s$) where the three light quarks are in a color-octet state. We find that (i) the LHCb ${P}_{c}$ states fall in the mass region of the studied system, (ii) most pentaquarks should be broad states since their $S$-wave open-charm decays are allowed while the lowest state is the ${J}^{P}={\frac{1}{2}}^{\ensuremath{-}}$ $\mathrm{\ensuremath{\Lambda}}$-like pentaquark with probably the suppressed ${\ensuremath{\eta}}_{c}\mathrm{\ensuremath{\Lambda}}$ decay mode only, and (iii) the ${J}^{P}={\frac{5}{2}}^{\ensuremath{-}}$ states do not decay through the $S$ wave and their widths are not so broad. The masses and widths of the two LHCb ${P}_{c}$ baryons are compatible with such pentaquark states. We also explore the hidden-bottom and ${B}_{c}$-like partners of the hidden-charm states and find the possible existence of the pentaquarks which are lower than the relevant hadronic molecules.