The baryo-quarkonium picture for hidden-charm and bottom pentaquarks and LHCb $P_{\rm c}(4380)$ and $P_{\rm c}(4450)$ states

We study baryo-charmonium [ηc- and J/ψ-N⁎, ηc(2S)-, ψ(2S)- and χc(1P)-N] and baryo-bottomonium [ηb(2S)-, ϒ(2S)- and χb(1P)-N] bound states, where N is the nucleon and N⁎ a nucleon resonance. In the baryo-quarkonium model, the five qqqQQ¯ quarks are arranged in terms of a heavy quarkonium core, QQ¯, embedded in light baryonic matter, qqq, with q=u or d. The interaction between the QQ¯ core and the light baryon can be written in terms of the QCD multipole expansion. The spectrum of baryo-charmonium states is calculated and the results compared with the existing experimental data. In particular, we can interpret the recently discovered Pc(4380) and Pc(4450) pentaquarks as ψ(2S)-N and χc2(1P)-N bound states, respectively. We observe that in the baryo-bottomonium sector the binding energies are, on average, slightly larger than those of baryo-charmonia. Because of this, the hidden-bottom pentaquarks are more likely to form than their hidden-charm counterparts. We thus suggest the experimentalists to look for five-quark states in the hidden-bottom sector in the 10.4–10.9 GeV energy region.