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

Abstract

The $η$-$η^\prime$ pseudoscalar mixing angle and the gluonium content of the $η^\prime$ meson are deduced from an updated phenomenological analysis of $J/ψ$ 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 $ϕ_P=(40.7\pm 2.3)^\circ$. In presence of gluonium, the values for the mixing angle and the gluonic content of the $η^\prime$ wave function are $ϕ_P=(44.6\pm 4.4)^\circ$ and $Z^2_{η^\prime}=0.29^{+0.18}_{-0.26}$, respectively. The newly reported values of $B(J/ψ\toρπ)$ by the BABAR and BES Collaborations are crucial to get a consistent description of data.

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