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Small Momentum Evolution of the Extended Drell--Hearn--Gerasimov Sum Rule

Véronique Bernard, Norbert Kaiser, Ulf-G. Meißner

hep-pharXiv:hep-ph/9212257

Abstract

We investigate the momentum dependence of the extended Drell-Hearn-Gerasimov sum rule. An economical formalism is developed which allows to express the extended DHG sum rule in terms of a single virtual Compton amplitude in forward direction. Rigorous results for the small momentum evolution are derived from chiral perturbation theory within the one-loop approximation. Furthermore, we evaluate some higher order contributions arising from Δ(1232) intermediate states and relativistic corrections. (2 figures available upon request).

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