Production of resonances in photon-photon collisions

The subject of production of resonances via two photons in e/sup +/e- colliding beams has finally come into its own. In particular, the eta meson is already changing from this year's sensation to next year's normalization. As for the other old physics mesons with even charge conjugation it seems likely that measurements of the scalar and tensor mesons coupling to two photons are quite doable and will be forthcoming. These will yield some interesting information on the quark content of these states and/or the dynamics of their two photon decays. As for the charmonium states, a measurement of some of the two photon decay widths would be quite interesting in terms of the information it gives on the dynamics of this system. However, even at LEP energies the cross sections for production of any particular state are rather small and one must be lucky to have a detectable decay mode or modes with substantial branching fraction. Finally, there is the ..pi../sup 0/ which started the whole subject. A measurement of this coupling is much easier using the complementary technique for determining two photon widths-the Primakoff effect. GAMMA(..pi../sup 0/ ..-->.. ..gamma gamma..) has long since been measured with high accuracy in this way