Quarkonia

Besides the spectra, the fine and hyperfine structure the author discusses radiative transitions in some detail. Some time is devoted to the puzzling states X(2.83), chi(3.45) and chi(3.59/3.18). As an application of QCD the author describes the gluonic annihilation of Quarkonia, which leads to the total hadronic decay width via a nonperturbative dressing mechanism. With the experimentally accessible regime of c.m. energies of 10 GeV or more, the gluons which govern annihilations in QCD, might show up as hadron jets. These jets should carry the directed momentum of the initial gluon. In angular distributions of these jets one should be able to measure gluon helicities. One can further speculate on the existence of glueballs in Quarkonium decays. It is rather difficult, however, to find an easy test of the nonabelian gluon self coupling. Nevertheless, finding the gluons is very important: they are the gauge bosons of QCD and a proof of their existence is as crucial for QCD as a proof of the existence of Z0 and W+- for the Salam-Weinberg theory. (Auth.)