Pentaquarks with hidden charm as hadroquarkonia

TL;DR

This paper models hidden charm pentaquarks as hadroquarkonium states, explaining the LHCb $P_c(4450)$ as a bound state with specific quantum numbers, and predicts a family of related states with calculated masses and decay widths.

Contribution

It introduces a QCD-inspired hadroquarkonium model for pentaquarks, providing detailed predictions for their masses, widths, and quantum numbers, and compares this with molecular models.

Findings

The $P_c(4450)$ is interpreted as a $ ext{ψ'}$-nucleon bound state.

Predicted pentaquark octets have small widths and satisfy Gell-Mann-Okubo relations.

Calculated decay widths agree with experimental data.

Abstract

We consider hidden charm pentaquarks as hadroquarkonium states in a QCD inspired approach. Pentaquarks arise naturally as bound states of quarkonia excitations and ordinary baryons. The LHCb $P_c(4450)$ pentaquark is interpreted as a $\psi'$-nucleon bound state with spin-parity $J^P=3/2^-$. The partial decay width $\Gamma(P_c(4450)\to J/\psi+N)\approx 11$ MeV is calculated and turned out to be in agreement with the experimental data for $P_c(4450)$. The $P_c(4450)$ pentaquark is predicted to be a member of one of the two almost degenerate hidden-charm baryon octets with spin-parities $J^{P}=1/2^-,3/2^-$. The masses and decay widths of the octet pentaquarks are calculated. The widths are small and comparable with the width of the $P_c(4450)$ pentaquark, and the masses of the octet pentaquarks satisfy the Gell-Mann-Okubo relation. Interpretation of pentaquarks as loosely bound $\Sigma_c\bar D^*$ and $\Sigma_c^*\bar D^*$ deuteronlike states is also considered. We determine quantum numbers of these bound states and calculate their masses in the one-pion exchange scenario. The hadroquarkonium and molecular approaches to exotic hadrons are compared and the relative advantages and drawbacks of each approach are discussed.