Unitarity constraints on radiative ϒ decays and possible interpretations of ζ(8.32)

If ζ is a scalar or pseudoscalar meson whose decay rate of less than 80 MeV is given by two gluon decays, the decay ? → γ + ζ with its branching ratio of ≈5 × 10^?3 cannot be mediated by gluonic interaction between ζ and the ?, if perturbative QCD is applicable to this reaction and if absorptive and dispersive parts are of comparable magnitude. Similar, though less stringent arguments apply for tensor mesons and no conflict arises for axial vector states. If ζ is a gluino ball and if b? is lighter than expected on theoretical grounds, the predicted rate is compatible with experiment. The experimental limit $\text{Br(? ′ → γ + ζ)}\text{Br(? → γ + ζ)}\text{< 0.22}$ cannot be accomodated within this framework.