Revisiting hidden-charm pentaquarks from QCD sum rules

TL;DR

This paper uses QCD sum rules to analyze the nature of the hidden-charm pentaquark states $P_c(4380)$ and $P_c(4450)$, proposing specific spin-parity assignments and discussing alternative possibilities.

Contribution

It introduces a refined QCD sum rule approach with a focus on pole contribution to identify the quantum numbers of pentaquark states.

Findings

$P_c(4380)$ likely has $J^P=3/2^-$

$P_c(4450)$ likely has $J^P=5/2^+$

Alternative spin-parity assignments remain possible

Abstract

We revisit the hidden-charm pentaquark states $P_c(4380)$ and $P_c(4450)$ using the method of QCD sum rules by requiring the pole contribution to be larger than or around 30\% to better insure the one-pole parametrization to be valid. We find two mixing currents and our results suggest that the $P_c(4380)$ and $P_c(4450)$ can be identified as hidden-charm pentaquark states having $J^P=3/2^-$ and $5/2^+$, respectively, while there still exist other possible spin-parity assignments, such as $J^P=3/2^+$ and $J^P=5/2^-$, which needs to be clarified in further theoretical and experimental studies.