Regge Effects in Weak Amplitudes

Recently Regge effects have been studied in weak amplitudes by describing the final-state strong interaction with a Regge pole at J=φ(t). In particular, it has been shown that the double-helicity-flip amplitude A₁(s,t) for the process γπ→γπ has a moving pole at J=φ(t)-2 and a fixed pole at J=-1, and that the electromagnetic form factor of the pion, F_π(s), can be written as F_π(s)=1+GP(s)+G_ρ(s), where G_ρ(s)→s^φ(0)-1[1+O(1/lns)]. In the present paper, we demonstrate how these results can be obtained by a simple and direct method that draws out an immediate physical understanding of the results obtained. Our method involves the study of the asymptotic behavior of the relevant field-theoretic diagrams with the use of Sudakov variables.