Feynman Rules for Reggeons

Rules are formulated for the evaluation of Feynman diagrams in which the virtual lines represent infinite multiplets with discrete and/or continuous spectra. In the simplest case this is a theory of Reggeon Feynman diagrams. The fact that infinite multiplets can represent multiparticle states with continuous mass spectra is emphasized, and a special case of "Compton" scattering via two-particle intermediary states is studied in detail. The kinematical structure of the amplitudes is fixed by the vertices, and is physically reasonable in all channels, particularly near $u=0\mathrm{}$ in unequal-mass scattering. This allows a particularly convenient empirical representation of the dynamics. It should be emphasized that the mass spectra of the infinite multiplets are perfectly general, and that no higher symmetry is implied.