The two-photon process for particle production in colliding beam experiments

A comparison is made, for various two-photon processes (ee → eeπ0, eeµ+ µ–, eeπ+ π–), between an exact calculation on the one hand and two alternative forms of the equivalent photon approximation (namely, the Low formula and the Dalitz-Yennie formula) on the other hand. Angular distributions of the particles produced are considered, as well as total cross sections