Fixed poles of photonic amplitudes involving compositeness

Abstract

The existence and significance of the right-signature J = 0 fixed pole in vector scattering such as photoproduction and Compton scattering off protons and pions is investigated in the context of gauge-invariant models involving compositeness which have been developed in a previous paper. It is shown that the existence of such a fixed pole depends on the elementarity of the photon and not on the compositeness of the pion or proton target or on the assumption that the charged constituent of the target has no structure. Assuming the p meson Iies on a Regge trajectory, we show that within the context of these models a J = 0 fixed pole does not arise in p-meson photoproduction.