Studying nuclear medium modification using the Gerasimov-Drell-Hearn sum rule

TL;DR

This paper explores how the Gerasimov-Drell-Hearn sum rule can be used to study modifications of nucleon properties within a nuclear medium, linking measurable observables to underlying nuclear effects.

Contribution

It demonstrates the application of the GDH sum rule to constrain the mechanisms of nucleon medium modification and highlights measurable global properties of embedded nucleons.

Findings

Sum rule relates cross-section to nucleon magnetic moment and mass.

Quadratic averaging constrains medium modification mechanisms.

Global properties like axial charge are accessible via sum rules.

Abstract

The Gerasimov-Drell-Hearn sum rule is a generic relation that has been used to make significant contributions to research in hadronic physics. It connects the spin-dependent cross-section for photoproduction off a particle to the squared ratio of the particle's anomalous magnetic moment and its mass, $(\kappa/M)^2$. Thus, for a nucleon embedded in a nucleus, the sum rule relates the cross-section to $\kappa/M$ averaged quadratically over the nucleons comprising the nucleus. This quadratic averaging can be used to constrain the mechanism responsible for the medium modification of the nucleon. We also point out that the global properties of the embedded nucleon like its axial charge, mass or magnetic moment are observables measurable through sum rules.