Final-state interaction in spin asymmetry and GDH sum rule for incoherent pion production on the deuteron
Institut für Kernphysik, Johannes Gutenberg-Universität, D-55099, Mainz, Germany
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The contribution of incoherent single-pion photoproduction to the spin response of the deuteron, i.e., the asymmetry of the total photoabsorption cross-section with respect to parallel and antiparallel spins of photon and deuteron, is calculated over the region of the $\Delta$-resonance with inclusion of final-state NN and $\pi N$ rescattering. Sizeable effects, mainly from NN rescattering, are found leading to an appreciable reduction of the spin asymmetry. Furthermore, the contribution to the Gerasimov-Drell-Hearn integral is explicitly evaluated by integration up to a photon energy of 550 MeV. Final-state interaction reduces the value of the integral to about half of the value obtained for the pure impulse approximation.
© Società Italiana di Fisica and Springer-Verlag, 2003