Identiication of the Glueballs and the Scalar Meson Nonet of Lowest Mass 1

We discuss the theoretical expectations and phenomenological evidence for the lightest glueballs and the members of the meson nonet with quantum numbers J PC = 0 ++. We reconsider the recent evidence for candidate states with masses below 1700 MeV, but include also the results from earlier phase-shift analyses. Arguments are presented to classify the scalars f 0 (980) and f 0 (1500) as members of the 0 ++ nonet, with a mixing rather similar to that of the pseudoscalars 0 and. The S-wave states called f 0 (400 ? 1200) and f 0 (1370) are considered as diierent signals from a single broad resonance, which we take to be the lowest-lying 0 ++ glueball. This state together with (1440) and f J (1710) with spin J = 2 form the basic triplet of binary gluonic bound states. We argue that these hypotheses are consistent with what can be expected theoretically.