We investigate the hadronic two-body decay modes of the scalar-isoscalar f 0 (1370), f 0 (1500) and f 0 (1710) states as resulting from the mixture of the lowest lying scalar glueball with the isoscalar states of the ground state 3 P 0 QQ nonet. In the decay analysis we take into account the direct coupling of the quarkonia and glueball components of the f 0 states to the quarkonia components of the two-meson final state with the decay dynamics inspired by the strong coupling limit of QCD. We calculate partial decay widths for the f 0 states in the proposed three-state mixing schemes and discuss their compatibility with the observed decay features. Finally, we determine the glueball-quarkonia content of the f 0 states from a detailed fit to experimental decay data of f 0 (1500) and give predictions for the partial decay widths of f 0 (1370) and f 0 (1710), providing thus a sensitive test of the proposed mixing scheme.

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A detailed analysis of the radiative pp annihilation is made in the framework of a two-step formalism, the pp annihilates into meson channels containing a vector meson with a subsequent conversion into a photon via the vector dominance model (VDM). Both steps are derived from the underlying quark model. First, branching ratios for radiative protonium annihilation are calculated and compared with data. Then, details of the isospin interference are studied for different models of the initial protonium state and also for different kinematical form factors. The isospin interference is shown to be uniquely connected to the pp − nn mixing in the protonium state. Values of the interference terms directly deduced from data are consistent with theoretical expectations, indicating a dominant pp component for the 1 S 0 and a sizable nn component for the 3 S 1 protonium state. The analysis is extended to the pp → γΦ transition, where the large observed branching ratio remains unexplained in the VDM approach.

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