Scalar glueball-qqbar mixing above 1 GeV and implications for lattice QCD

Lattice QCD predictions have motivated several recent studies of the mixing between the predicted J(PC) = 0(++) glueball and a q (q) over bar nonet in the 1.3 --> 1.7 GeV region. We show that results from apparently different approaches have some common features, explain why this is so and abstract general conclusions. We place particular emphasis on the flavour dependent constraints imposed by decays of the f(0)(1370), f(0)(1500) and f(0)(1700) to all pairs of pseudoscalar mesons. From these results we identify a systematic correlation between glueball mass, mixing, and flavour symmetry breaking and conclude that the glueball may be rather lighter than some quenched lattice QCD computations have suggested. We identify experimental tests that can determine the dynamics of a glueball in this mass region and discuss quantitatively the feasibility of decoding glueball-q (q) over bar mixing.