J/ψ → VP decays and the quark and gluon content of the η and η′

The eta-eta' pseudoscalar mixing angle and the gluonium content of the eta' 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-flavor basis is found to be phi(P) = (40.7 +/- 2.3)degrees. In presence of gluonium, the values for the mixing angle and the gluonic content of the eta' wave function are phi(P) = (44.6 +/- 4.4)degrees and Z(eta')(2) = 0.29(-0.26)(+ 0.18), respectively. The newly reported values of B(J/psi -> rho pi) by the BABAR and BES Collaborations are crucial to get a consistent description of the data.