Spin structure of the nucleon at low energies
Hermann Krebs (Bochum)

The internal spin structure of the nucleon is described by structure functions in deep inelastic lepton-hadron scattering which are related to real, virtual and double virtual Compton scattering amplitudes by various sum rules connecting information at all energy scales. One of the main goals of Jefferson Lab activities is to provide a precise experimental mapping of spin-dependent observables from low-momentum transfer to multi-GeV region. In my talk I will concentrate on theoretical description of spin polarizabilities of double virtual Compton scattering. We use chiral perturbation theory to describe low energy QCD dynamics in a model independent way. I will review earlier chiral perturbation theory activities in this field and will show that new Jefferson Lab experimental data at low virtuality can be better described once Delta resonance degrees of freedom are taken into account explicitly.