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

TL;DR

This paper models hidden-charm and bottom pentaquarks as bound states of heavy quarkonium cores within light baryonic matter, successfully interpreting recent LHCb pentaquark discoveries and predicting more states in the bottom sector.

Contribution

It introduces a baryo-quarkonium model using QCD multipole expansion to interpret pentaquarks and predicts the existence of hidden-bottom pentaquarks in the 10.4-10.9 GeV range.

Findings

P_c(4380) and P_c(4450) are interpreted as bound states of $ ext{ψ(2S)}$-$N$ and $ ext{χ}_{c2}(1P)$-$N$.

Hidden-bottom pentaquarks are predicted to have larger binding energies and are more likely to be observed.

Suggested experimental search in the 10.4-10.9 GeV energy region for hidden-bottom pentaquarks.

Abstract

We study baryo-charmonium [$\eta_{\rm c}$- and $J/\psi$-$N^*$, $\eta_{\rm c}(2S)$-, $\psi(2S)$- and $\chi_{\rm c}(1P)$-$N$] and baryo-bottomonium [$\eta_{\rm b}(2S)$-, $\Upsilon(2S)$- and $\chi_{\rm b}(1P)$-$N$] bound states, where $N$ is the nucleon and $N^*$ a nucleon resonance. In the baryo-quarkonium model, the five $qqq Q \bar Q$ quarks are arranged in terms of a heavy quarkonium core, $Q \bar Q$, embedded in light baryonic matter, $qqq$, with $q = u$ or $d$. The interaction between the $Q \bar Q$ 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 $P_{\rm c}(4380)$ and $P_{\rm c}(4450)$ pentaquarks as $\psi(2S)$-$N$ and $\chi_{\rm c2}(1P)$-$N$ 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.