The Generalized GDH Sum Rule: Measuring the Spin Structure of $\mathrm{^3He}$ and the Neutron using Nearly Real Photons

The Gerasimov-Drell-Hearn (GDH) sum rule is one of the most important tools available to study nucleon spin structure. Originally derived for real photon absorption ($Q^2=0$), the GDH sum rule has been generalized to finite $Q^2$. The goals of Jefferson Lab experiment E97-110 are to measure the $Q^2$ dependence of the GDH integral between 0.02 and 0.3 $(\mathrm{GeV}/c)^2$, to study the slope of the GDH integral at $Q^2 \approx 0$, and to extrapolate to the real photon point for $\mathrm{^3He}$ and the neutron. In this domain, the measurement of the generalized GDH integral tests Chiral Perturbation Theory and probes its limits of applicability at low $Q^2$. The low $Q^2$ measurements from this experiment will provide new constraints on understanding the $\mathrm{^3He}$ and neutron spin structure and a better understanding of the effect of nucleon resonances. Data collection was completed in August 2003 using the Jefferson Lab high polarization continuous electron beam and a polarized $\mathrm{^3He}$ target. The status of the data analysis and future perpectives will be discussed.