RADIATIVE DECAY OF VECTOR QUARKONIUM - CONSTRAINTS ON GLUEBALLS AND LIGHT GLUINOS

Given a resonance of known mass, width, and J(PC), we can determine its gluonic branching fraction b(R-->gg) from data on its production in radiative vector quarkonium decay V --> gamma R. For most resonances b(R-->gg) is found to be similar to 10%, consistent with being q ($) over bar q states, but we find that both pseudoscalars-observed in the 1440 MeV region have b(R-->gg) similar to 1/2 - 1 and b(f(0++) --> gg) similar to 1/2. As data improve, b(R-->gg) should be a useful discriminator between q ($) over bar q and gluonic states and may permit quantitative determination of the extent to which a particular resonance is a mixture of glueball and qa. We also examine the regime of validity of PQCD for predicting the rate of V --> gamma eta ($) over bar g, the ''extra'' pseudoscalar bound state which would exist if there were light gluinos. From the CUSB limit on peaks in Upsilon --> gamma X, the mass range 3 GeV less than or similar to m(eta ($) over bar g) similar to 7 GeV can be excluded. An experiment must be significantly more sensitive to exclude an eta ($) over bar g lighter than this.