Heavy pentaquark states and a novel color structure

TL;DR

This paper introduces a new pentagonal color flux-tube structure for heavy pentaquark states, providing a theoretical framework that explains certain observed states and predicts new heavy pentaquarks with specific configurations.

Contribution

It proposes a novel pentagonal color flux-tube structure within the flux-tube model, explaining the structure of some pentaquark states and predicting new heavy pentaquark states.

Findings

The pentagonal structure has the lowest energy among flux-tube configurations.

The state P_c(4380) fits the model as a compact pentaquark with this structure.

P_c(4450) cannot be explained by the flux-tube model.

Abstract

Encouraged by the observation of the pentaquark states $P^+_c(4380)$ and $P^+_c(4450)$, we propose a novel color flux-tube structure, pentagonal state, for pentaquark states within the framework of color flux-tube mode involving a five-body confinement potential. Numerical results on the heavy pentaquark states indicate that the states with three color flux-tube structures, diquark, octet and pentagonal structures, have the close masses, which can therefore be called QCD isomers analogous to isomers in Chemistry. The pentagonal structure has lowest energy. The state $P^+_c(4380)$ can be described as the compact pentaquark state $uudc\bar{c}$ with the pentagonal structure and $J^P=\frac{3}{2}^-$ in the color flux-tube model. The state $P^+_c(4450)$ can not be accommodated into the color flux-tube model. The heavy pentaquark states $uudc\bar{b}$, $uudb\bar{c}$ and $uudb\bar{b}$ are predicted in the color flux-tube model. The five-body confinement potential basing on the color flux-tube picture as a collective degree of freedom is a dynamical mechanism in the formation of the compact heavy pentaquark states.