J/psi->VP decays and the quark and gluon content of the eta and eta'

Abstract

The $\eta$-${\eta }^{\prime }$ pseudoscalar mixing angle and the gluonium content of the ${\eta }^{\prime }$ meson are deduced from an updated phenomenological analysis of $J/\psi$ decays into a vector and a pseudoscalar meson. In absence of gluonium, the value of the mixing angle in the quark-flavour basis is found to be ${\varphi }_P=(40.7\pm 2.3{)}^{\circ }$. In presence of gluonium, the values for the mixing angle and the gluonic content of the ${\eta }^{\prime }$ wave function are ${\varphi }_P=(44.6\pm 4.4{)}^{\circ }$ and $Z_{{\eta }^{\prime }}^2=0.29_{-0.26}^{+0.18}$, respectively. The newly reported values of $B(J/\psi \to \rho \pi )$ by the BABAR and BES Collaborations are crucial to get a consistent description of data.

Comments: 7 pages, 1 figure, uses svjour style. Comments on the relationship between J/psi to VP and V to Pgamma decays and on the neglected contributions together with an asymmetric treatment of errors are included