1. MAID and the GDH sum rule in the resonance region
Dieter Drechsel, Sabit Kamalov and Lothar Tiator
Institut für Kernphysik
Universität Mainz
electromagnetic sum rules
new MAID developments
comparison with exclusive data
model calculations of sum rules
comparison with JLAB data at Q2 > 0
summary

4. the observed spin structure of the nucleon
depends on the resolution of the probe:
current quarks
sea quarks
gluons
orbital angular momentum
constituent quarks
and pion cloud
resonance phenomena
deep inelastic scattering

5. Nucleon Compton Scattering
Forward Compton Amplitude
non spin-flip
spin-flip
Low Energy Theorems
Helicity

6. Optical Theorem due to Unitarity
Dispersion Relations lead to Sum Rules
does not converge

7. Similar for the Spin Amplitude

8. Summary of various Sum Rules

32. Summary
polarized photo absorption on the proton target s3/2 - s1/2 is reasonably well understood for the resonance region with 1p + 2p + h production
exclusive channels are very important in nucleon resonance analysis, e.g. D13(1520)
the GDH integral for the proton is not yet saturated in the resonance region Wcm < 2 GeV
resonance models overestimate the GDH for the proton and underestimate the GDH for the neutron, e.g.: MAID02+RPR gives approximately: Ip  mb (proton) GDH(p) - Ip  +20 mb In  mb (neutron) GDH(n) - In  -33 mb
situation with the proton target at Q2 > 0 : results from JLAB/CLAS show reasonable agreement
situation with the neutron target at Q2 > 0 : results from Hall A on 3He show up to 40% disagreement for small Q² (below 0.4 GeV²), the agreement is much better for larger Q²