The electromagnetic form factors of $\hat{I}\pounds$ and $\hat{I}{\pounds }^0\to \hat{I}›$ transition in the timelike region

Abstract

We investigate the $e^{+}{e}^{-}\to \hat{I}\pounds \bar{\hat{I}}\pounds$ and $e^{+}{e}^{-}\to \hat{I}›\bar{\hat{I}}{\pounds }^0$ reactions within the extended vector meson dominance model. In addition to the ground state mesons $\ddot{I}$ and $\ddot{I}‰$, we consider the contributions of the excited states $\ddot{I}(3D)$, $\ddot{I}‰(3D)$, $\ddot{I}•(3D)$, and $\ddot{I}(6D)$. It is found that the current experimental data on the $\hat{I}\pounds$ electromagnetic form factors in timelike region can be well reproduced. And the $\ddot{I}•(3D)$ resonance is essential to the near threshold enhancement of the cross section for the $e^{+}{e}^{-}\to \hat{I}\pounds \bar{\hat{I}}\pounds$ reaction. Furthermore, in the $e^{+}{e}^{-}\to \hat{I}›\bar{\hat{I}}{\pounds }^0$ reaction, the $\ddot{I}(3D)$ is important to get a good fit for the experimental results.

17 pages, 10 figures