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

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.

Comments: 22 pages, 5 figures