Resonance production in γγ collisions. 2

The assumption of vector dominance for both photons in γγ-collisions leads us to the expectation that elastic scattering and charge-exchange reactions will occur from a variety of incoming vector mesons, with the attendant resonance formation and t-channel exchanges. We will examine data on vector-meson production and its Q2-dependence to test this picture. In doing so we encounter hints of a variety of intriguing objects permitted by QCD, such as four-quark states and glueballs. We finally give a status report on γγ-excitation of Charmonium states, a subject still in its infancy. (Auth.)