Higher moments of nucleon spin structure functions in heavy baryon chiral perturbation theory and in a resonance model

The third moment d2 of the twist-3 part of the nucleon spin structure function g2 is generalized to arbitrary momentum transfer Q2 and is evaluated in heavy baryon chiral perturbation theory (HBChPT) up to order Ο(p4) and in a unitary isobar model (MAID). We show how to link d2 as well as higher moments of the nucleon spin structure functions g1 and g2 to nucleon spin polarizabilities. We compare our results with the most recent experimental data, and find a good description of these available data within the unitary isobar model. We proceed to extract the twist-4 matrix element f2 which appears in the 1/Q2 suppressed term in the twist expansion of the spin structure function g1 for proton and neutron