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Dieter Drechsel, Sabit Kamalov and Lothar Tiator Institut für Kernphysik Universität Mainz

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

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Dieter Drechsel, Sabit Kamalov and Lothar Tiator Institut für Kernphysik Universität Mainz

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  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

  2. 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

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

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

  5. Similar for the Spin Amplitude

  6. Summary of various Sum Rules

  7. Summary • polarized photo absorption on the proton targets3/2 - 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 - 225 mb (proton) GDH(p) - Ip  +20mb In - 200 mb (neutron) GDH(n) - In  -33mb • 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

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