On the quantum numbers of the $X(1880)$

TL;DR

This paper investigates the properties of the $X(1880)$ resonance near the $ar{p}p$ threshold, suggesting it is an isoscalar $0^{-+}$ state generated by threshold effects, using a detailed amplitude analysis.

Contribution

The study introduces a novel analysis incorporating nucleon-antinucleon rescattering and the distorted wave Born approximation to determine the quantum numbers of $X(1880)$.

Findings

$X(1880)$ is likely an isoscalar $0^{-+}$ state.

The resonance is generated by threshold behavior.

Rescattering effects are crucial in the analysis.

Abstract

We study the properties of the $X(1880)$, the structure around the $\bar{p}p$ threshold that appears in the $3(\pi^+\pi^-)$ invariant mass spectrum in the decay process of $J/\psi \to \gamma 3(\pi^+\pi^-)$. Nucleon-antinucleon rescattering is taken into account in our analysis, and the decay amplitude of $J/\psi \to \gamma 3(\pi^+\pi^-)$ can be obtained by the distorted wave Born approximation. With these amplitudes, we analyze the contributions to the $X(1880)$ from different partial waves. Our analysis suggests that the $X(1880)$ should be isoscalar $0^{-+}$, and it is generated by the threshold behavior.