The Drell-Hearn-Gerasimov Sum Rule
Abstract
The Drell-Hearn-Gerasimov (DHG) sum rule relates the helicity structure of the photoabsorption cross section to the anomalous magnetic moment of the nucleon. It is based on Lorentz and gauge invariance, crossing symmetry, causality and unitarity. A generalized DHG sum rule my be derived for virtual photons. At low momentum transfer this generalized sum rule is saturated by the resonance region, at high momentum transfer it may be expressed by the parton spin distributions measured in deep inelastic scattering. The longitudinal-transverse interference determines the Cottingham sum rule, which is related to the electric and magnetic form factors over the whole range of momentum transfer.
Keywords
Cite
@article{arxiv.nucl-th/9411034,
title = {The Drell-Hearn-Gerasimov Sum Rule},
author = {D. Drechsel},
journal= {arXiv preprint arXiv:nucl-th/9411034},
year = {2009}
}
Comments
20 pages LATEX plus 12 figures (available by fax from the author)