Vacuum exchange amplitudes from a family of sum rules

Abstract

The properties of vacuum-exchange amplitudes in high energy πN scattering are deduced from a family of generalized superconvergent sum rules, through a range of t. The t-channel non-flip amplitude A′ + agrees with some P + P′ Regge pole models, preferring the “no-compensation” mechanism. The t-channel flip amplitude B + differs in size and sign from what has normally been assumed. The sum rules suggest an approximate relation νB + ≈ A′ +. A Regge pole fit to data including this ansatz gives good agreement with the A′ + sum rule, and semi-quantitative agreement with B + sum rules.