Azimuthal correlations in photon-photon collisions

Using the general helicity formula for γ^*γ^* collisions, we show that it should be possible to determine a number of independent ``structure functions,'' i.e., linear combinations of elements of the two-photon helicity tensor, through azimuthal correlations in two-body or quasi-two-body reactions induced by the photon-photon interaction, provided certain experimental conditions are satisfied. Numerical results of our computations are presented for some particular processes and dynamic models.