The perturbative reggeon calculus: building reggeon cuts from reggeon tree graphs

Presents a discussion of the derivation of the reggeon calculus from perturbation theory. The method is illustrated with a simple example of the reggeon-particle cut in the 2-to-2 amplitude, not published hitherto. A possible derivation of the calculus based on the dual resonance model and an idea of Veneziano's is also mentioned. The second part consists of a discussion of the s-channel discontinuities of the two-reggeon graph which also relies on the analytic structure of the multi-Regge tree graphs in a particularly interesting way. Also included in this section are some provocative remarks about the reliability of theories based strictly on the J-plane analysis. (11 refs).