Measurements of<i>J/ψ</i>decays into a vector and a pseudoscalar meson

We present measurements of the two-body decays of the J/\ensuremath{\psi} into a vector and a pseudoscalar meson. The data, taken with the Mark III detector at the SLAC ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ storage ring SPEAR, consist of 5.8\ifmmode\times\else\texttimes\fi{}${10}^{6}$ produced J/\ensuremath{\psi}'s. The branching ratios for the J/\ensuremath{\psi} decays into \ensuremath{\rho}\ensuremath{\pi}, \ensuremath{\rho}\ensuremath{\eta}, \ensuremath{\rho}\ensuremath{\eta}', \ensuremath{\omega}${\ensuremath{\pi}}^{0}$, \ensuremath{\omega}\ensuremath{\eta}, \ensuremath{\omega}\ensuremath{\eta}', \ensuremath{\varphi}\ensuremath{\eta}, \ensuremath{\varphi}\ensuremath{\eta}', and ${K}^{\mathrm{*}}$K are measured; an upper limit on J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\varphi}${\ensuremath{\pi}}^{0}$ is obtained. Using the measured branching ratios we obtain parameters of a phenomenological model of J/\ensuremath{\psi} decays, indicating that the \ensuremath{\eta} and \ensuremath{\eta}' are consistent with being composed only of light and strange quarks. The model is used to obtain the mixing angle in the pseudoscalar nonet. The \ensuremath{\omega}${\ensuremath{\pi}}^{0}$ electromagnetic form factor is determined. The upper limit on J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\varphi}${\ensuremath{\pi}}^{0}$ is used to study the contributions from electromagnetic doubly--Okubo-Zweig-Iizuka--suppressed decays of the J/\ensuremath{\psi}. .AE