SUMS OF THE SEARCH FOR 4-QUARK STATES IN GAMMA-GAMMA COLLISIONS

A review of the results of the search for four-quark states in gamma-gamma collisions during the last decade is presented. The resonance phenomena in the reactions gamma-gamma --> rho-0-rho-0, gamma-gamma --> rho+rho-, gamma-gamma --> omega-rho-0, gamma-gamma --> K*KBAR*, gamma-gamma --> omega-omega, gamma-gamma --> phi-V, gamma-gamma --> pi-0-eta, gamma-gamma --> pi-pi are discussed in detail. In particular, it is shown that presently there are telling arguments for observation of a tensor exotic q2q2BAR resonance with isospin I = 2 near the rho-rho threshold un gamma-gamma --> rho-0-rho-0, gamma-gamma --> rho+rho-. A set of new experiments for the elucidation of the physical nature of the considered phenomena is also suggested.