Nature of the $Y(4260)$: A light-quark perspective

TL;DR

This study investigates the internal structure of the enigmatic $Y(4260)$ particle, revealing it likely contains significant light-quark components and is not a simple hybrid or charmonium state, based on analysis of decay spectra and SU(3) symmetry effects.

Contribution

The paper introduces a light-quark perspective and employs dispersion theory to analyze the $Y(4260)$, highlighting the role of SU(3) octet states and challenging previous hybrid or charmonium interpretations.

Findings

$Y(4260)$ has a large light-quark component.

SU(3) octet state influences decay processes.

$Y(4260)$ is not a hybrid or pure charmonium.

Abstract

The $Y(4260)$ has been one of the most puzzling pieces among the so-called $XYZ$ states. In this paper, we try to gain insights into the structure of the $Y(4260)$ from the light-quark perspective. We study the dipion invariant mass spectrum of the $e^+ e^- \to Y(4260) \to J/\psi \pi^+\pi^-$ process and the ratio of the cross sections ${\sigma(e^+e^- \to J/\psi K^+ K^-)}/{\sigma(e^+e^- \to J/\psi \pi^+\pi^-)}$. In particular, we consider the effects of different light-quark SU(3) eigenstates inside the $Y(4260)$. The strong pion-pion final-state interactions as well as the $K\bar{K}$ coupled channel in the $S$-wave are taken into account in a model-independent way using dispersion theory. We find that the SU(3) octet state plays a significant role in these transitions, implying that the $Y(4260)$ contains a large light-quark component. Our findings suggest that the $Y(4260)$ is neither a hybrid nor a conventional charmonium state, and they are consistent with the $Y(4260)$ having a sizeable $\bar D D_1$ component which, however, is not completely dominant.