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-→Y(4260)→J/ψπ+π- process and the ratio of the cross sections σ(e+e-→J/ψK+K-)/σ(e+e-→J/ψπ+π-). 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 KK̄ 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 DD1 component which, however, is not completely dominant.