Hidden-Bottom Pentaquarks

TL;DR

This study extends the analysis of pentaquark states to the hidden-bottom sector using a chiral quark model, predicting negative parity molecular-like bound states with larger binding energies than in the hidden-charm sector.

Contribution

The paper provides the first detailed theoretical investigation of hidden-bottom pentaquarks, exploring their possible quantum numbers, structures, and binding energies using an extended chiral quark model.

Findings

Negative parity hidden-bottom pentaquarks are predicted.

Molecular-type structures are favored with color-singlet configurations.

Hidden-color configurations lead to deeply bound states with larger binding energies.

Abstract

The LHCb Collaboration has recently reported strong evidences of the existence of pentaquark states in the hidden-charm baryon sector, the so-called $P_c(4380)^+$ and $P_c(4450)^+$ signals. Five-quark bound states in the hidden-charm sector were explored by us using, for the quark-quark interaction, a chiral quark model which successfully explains meson and baryon phenomenology, from the light to the heavy quark sector. We extend herein such study but to the hidden-bottom pentaquark sector, analyzing possible bound-states with spin-parity quantum numbers $J^P=\frac12^\pm$, $\frac32^\pm$ and $\frac52^\pm$, and in the $\frac12$ and $\frac32$ isospin sectors. We do not find positive parity hidden-bottom pentaquark states; however, several candidates with negative parity are found with dominant baryon-meson structures $\Sigma_b^{(\ast)}\bar{B}^{(\ast)}$. The calculated distances among any pair of quarks within the bound-state reflect that molecular-type bound-states are favored when only color-singlet configurations are considered in the coupled-channels calculation whereas compact pentaquarks, which are also deeply bound, can be found when hidden-color configurations are added. Finally, our findings resemble the ones found in the hidden-charm sector but, as expected, we find in the hidden-bottom sector larger binding energies and bigger contributions of the hidden-color configurations.