Helicity dependence of the $overrightarrow{gamma}overrightarrow {N}rightarrowpi N$ reaction channels in the $Delta$ -resonance region

Abstract

Based on a prior effective Lagrangian model on single pion photoproduction from the nucleon, successfully tested in total and differential cross sections, the helicity dependence from the interaction of circularly polarized photons and a longitudinally polarized nucleon target is studied in the energy range from π-threshold through the $Delta$(1232)-resonance region. The doubly polarized total and differential cross section differences for parallel $sigma^{3/2}$ and antiparallel $sigma^{1/2}$ helicity states are predicted and compared with recent experimental data. We show that the results are sensitive to interferences among different contributions to the process and, thus, represent a complementary test of the theoretical model. A quite satisfactory agreement with recent experimental data from the GDH-collaboration is obtained.