Disentangling the role of the $Y(4260)$ in $e^{+}{e}^{-}\to D^{\ast }{\bar{D}}^{\ast }$ and $D_s^{\ast }{\bar{D}}_s^{\ast }$ via line shape studies

Abstract

Whether the $Y(4260)$ can couple to open charm channels has been a crucial issue for understanding its nature. The available experimental data suggest that the cross section line shapes of exclusive processes in $e^{+}{e}^{-}$ annihilations have nontrivial structures around the mass region of the $Y(4260)$. As part of a series of studies of the $Y(4260)$ as mainly a $\bar{D}{D}_1(2420)+c.c.$ molecular state, we show that the partial widths of the $Y(4260)$ to the two-body open charm channels of $e^{+}{e}^{-}\to D^{\ast }{\bar{D}}^{\ast }$ and $D_s^{\ast }{\bar{D}}_s^{\ast }$ are much smaller than that to $\bar{D}{D}^{\ast }\ddot{I}€+c.c.$. The line shapes measured by the Belle Collaboration for these two channels can be well described by the vector charmonium states $\ddot{I}ˆ(4040)$, $\ddot{I}ˆ(4160)$ and $\ddot{I}ˆ(4415)$ together with the $Y(4260)$. It turns out that the interference of the $Y(4260)$ with the other charmonia produces a dip around 4.22~GeV in the $e^{+}{e}^{-}\to D^{\ast }{\bar{D}}^{\ast }$ cross section line shape. The data also show an evidence for the strong coupling of the $Y(4260)$ to the $D{\bar{D}}_1(2420)$, in line with the expectation in the hadronic molecular scenario for the $Y(4260)$.

Revtex, 17 pages, 5 eps figures; Revised version to appear in Phys. Lett. B