Generalized Drell-Hearn-Gerasimov sum rule at order O(p(4)) in chiral perturbation theory

We calculate the forward spin-dependent photon-nucleon Compton amplitudes S -1 and S-2 as functions of photon energy nu and mass Q(2) at the next-to-le ading (O(p(4))) order in chiral perturbation theory, from which we extract the contribution to a generalized Drell-Hearn-Gerasimov sum rule at low Q(2 ). The result indicates a much rapid Q(2) variation of the sum rule than a simple dimensional analysis would yield. (C) 2000 Published by Elsevier Sci ence B.V. All rights reserved.