# New LHCb pentaquarks as hadrocharmonium states

## TL;DR

This paper interprets recent LHCb pentaquark discoveries within the hadrocharmonium framework, explaining their mass splittings, quantum numbers, and decay properties through QCD interactions and bound state models.

## Contribution

It provides a detailed hadrocharmonium interpretation of new pentaquark states, including hyperfine splitting estimates and explanations for observed mass and width patterns.

## Key findings

- The splitting of P_c(4450) into P_c(4440) and P_c(4457) matches hyperfine splitting predictions.
- The P_c(4312) is explained as a bound state of χ_c0 and a nucleon.
- A series of states near P_c(4380) can account for its large decay width.

## Abstract

New LHCb Collaboration results on pentaquarks with hidden charm [1] are discussed. These results fit nicely in the hadrocharmonium pentaquark scenario [2,3]. In the new data the old LHCb pentaquark $P_c(4450)$ splits into two states $P_c(4440)$ and $P_c(4457)$. We interpret these two almost degenerate hadrocharmonium states with $J^P=1/2^-$ and $J^P=3/2^-$ as a result of hyperfine splitting between hadrocharmonium states predicted in [2]. It arises due to QCD multipole interaction between color-singlet hadrocharmonium constituents. We improve the theoretical estimate of hyperfine splitting [2,3] that is compatible with the experimental data. The new $P_c(4312)$ state finds a natural explanation as a bound state of $\chi_{c0}$ and a nucleon, with $I=1/2$, $J^P=1/2^+$ and binding energy 42 MeV. As a bound state of a spin-zero meson and a nucleon, hadrocharmonium pentaquark $P_c(4312)$ does not experience hyperfine splitting. We find a series of hadrocharmonium states in the vicinity of the wide $P_c(4380)$ pentaquark that can explain its apparently large decay width. We compare the hadrocharmonium and molecular pentaquark scenarios and discuss their relative advantages and drawbacks.