Determining the Gluonic Content of Isoscalar Mesons

We develop tools to determine the gluonic content of a resonance of known mass, width and $J^{PC}$ from its branching fraction in radiative quarkonium decays and production cross section in $\gamma \gamma$ collisions. We test the procedures by applying them to known $q\bar{q}$ mesons, then analyze four leading glueball candidates. We identify inconsistencies in data for $J/\psi \to \gamma f_0(1500)$ and $J/\psi \to \gamma f_J(1710)$ whose resolution can quantify their glueball status.When $\Gamma(f_0(1500) \to \gamma \gamma )$ and $\Gamma(f_J(1710) \to \gamma \gamma)$ are known, the $n\bar{n}, s\bar{s},gg$ mixing angles can be determined. The enigmatic situation in 1400-1500 MeV region of the isosinglet $0^{-+}$ sector is discussed.