The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Nucleon

Abstract

The Gerasimov-Drell-Hearn sum rule is one of several dispersive sum rules that connect the Compton scattering amplitudes to the inclusive photoproduction cross sections of the target under investigation. Being based on such universal principles as causality, unitarity, and gauge invariance, these sum rules provide a unique testing ground to study the internal degrees of freedom that hold the system together. The present article reviews these sum rules for the spin-dependent cross sections of the nucleon by presenting an overview of recent experiments and theoretical approaches. The generalization from real to virtual photons provides a microscope of variable resolution: At small virtuality of the photon, the data sample information about the long range phenomena, which are described by effective degrees of freedom (Goldstone bosons and collective resonances), whereas the primary degrees of freedom (quarks and gluons) become visible at the larger virtualities. Through a rich body of new data and several theoretical developments, a unified picture of virtual Compton scattering emerges, which ranges from coherent to incoherent processes, and from the generalized spin polarizabilities on the low-energy side to higher twist effects in deep inelastic lepton scattering.

arXiv comment32 pages, 19 figures, review article

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Cited by in corpus (28)

• The Spin Structure of the Proton
• Electromagnetic Excitation of Nucleon Resonances
• The Spin Structure of the Nucleon
• The Theory of Deeply Inelastic Scattering
• Experimental determination of the effective strong coupling constant
• Determination of the effective strong coupling constant alpha_{s,g_1}(Q^2) from CLAS spin structure function data
• Moments of the Spin Structure Functions g_1^p and g_1^d for 0.05 < Q^2 < 3.0 GeV^2
• Hadron structure at low Q^2
• Sum Rules and Moments of the Nucleon Spin Structure Functions
• Sum Rules for Magnetic Moments and Polarizabilities in QED and Chiral Effective-Field Theory
• The Gerasimov-Drell-Hearn Sum Rule
• Factorization in Graviton Scattering and the "Natural" Value of the g-factor
• Moments of Spin Structure Functions: Sum Rules and Polarizabilities
• How Large is the "Natural" Magnetic Moment?
• The MAID Legacy and Future
• Spin-dependent sum rules connecting real and virtual Compton scattering verified
• Two-photon exchange on neutron and the hyperfine splitting
• Polarizability relations across real and virtual Compton scattering processes
• Polarizabilities of the nucleon and spin dependent photo-absorption
• First measurement of helicity-dependent cross sections in pi0-eta photoproduction from quasi-free nucleons
• Photo-absorption on deuteron contributed by d^*(2380) resonance
• Single-pion contribution to the Gerasimov--Drell--Hearn sum rule and related integrals
• Light-by-light scattering sum rule for radiative transitions of bottomonia
• A sign change of the moment at $n=0$ of the polarized structure function $g_1^p$
• Contribution of single pion electroproduction to the generalized Gerasimov-Drell-Hearn sum rule for the deuteron
• The Gerasimov-Drell-Hearn sum-rule with nuclear targets
• Two-photon physics
• Coupled-channel contributions to the GDH sum rule from the Jülich-Bonn approach