THE SPIN RESPONSE OF THE NUCLEON AND ITS IMPLICATION FOR THE GDH SUM RULE AND THE DOUBLE POLARIZATION E ASYMMETRY

摘要

The contribution of single-pion photoproduction channels to the spin response of the nucleon, i.e. the asymmetry of photoabsorption cross sections with respect to parallel and antiparallel spins of photon and nucleon, is calculated over the region of the Δ(1232)-resonance adopting an effective Lagrangian model for the reaction amplitude. Furthermore, the contribution from separate pion photoproduction channels to the Gerasimov-Drell-Hearn integral is explicitly evaluated by integration up to a photon lab-energy of 550 MeV. In addition, the double polarization E asymmetry for the individual pion photoproduction channels is predicted. A quite satisfactory agreement with recent experimental data from the GDH Collaboration is obtained.