Duality and high-energy behavior of a reggeon-reggeon amplitude in the dual resonance model

The analytic structure and high-energy behavior of the 2-reggeon → 2-particle amplitude is studied using a double helicity pole limit of the B6 function. In the high-energy limit the amplitude gets a contribution from the exchange of a new Regge trajectory β. The properties of β exchange and its implications for Regge theory and phenomenology are discussed. Because of the presence of cuts in the Toller variables, finite energy sum rules for reggeon-reggeon amplitudes are in general not saturated by s-channel dynamical singularities (resonances, thresholds). The additional contributions are, however, shown to be absent for certain discontinuities of the six-point amplitude which therefore have ordinary duality properties. The theoretical discussion is supplemented by numerical examples of the B6 function. (Auth.)