On the origin of the $Y(4260)$

Abstract

We study the relation between the $\psi(4160)$ and the $Y(4260)$ within an unitarized effective Lagrangian approach. The $Y(4260)$ arises as a manifestation of the $\psi(4160)$, when a loop-driven decay of the type $\psi(4160)\to D_s^*\bar{D}_s^*\to J/\psi f_0(980)$ is enhanced by the proximity of the pole, corresponding to the $\psi(4160)$, to the \emph{almost} closed $D_s^*\bar{D}_s^*$ decay channel. Other $f_0$ resonances that may add a non-negligible contribution, by the same mechanism, are not included for simplicity, but they are not expected to change the main conclusion. Within this picture, the $Y(4260)$ is not, therefore, an independent resonance, but rather a variation of the $\psi(4160)$, which also explains why it is not seen in OZI-allowed decay channels in the experiment.