Low-Energy Theorem for γγ-->3π and the Reaction γ+Z-->3π+Z

Recently a low-energy theorem was proposed by Adler, Lee, Treiman, and Zee and by Terent'ev for the reaction 2γ-->3π. This theorem is supposed to be valid at an unphysical point in the production amplitude. One possible way to test its reliability is to measure the reaction e⁺e^--->e⁺e^-+3π which unfortunately has a very small cross section. In this paper we investigate another reaction which may allow a more satisfactory check of the low-energy theorem, namely, the photoproduction of three pions off a target nucleus. Cross sections, angular and energy distributions, and invariant-mass plots are given for several beam energies assuming a lead target. The η-meson background is also examined.