First measurement of the helicity dependence of He-3 photoreactions in the Delta(1232) resonance region

The first measurement of the helicity dependence of the total inclusive He-3 photo-absorption cross section and of the partial cross sections for several reaction channels was carried out at MAMI (Mainz) in the photon energy range between 150 and 500 MeV. The experiment used the large acceptance Crystal Ball spectrometer, complemented by charged particle and vertex detectors, a circularly polarised tagged photon beam and a longitudinally polarised high-pressure He-3 gas target. The results obtained give information on the GDH integral on He-3 and on the neutron and allow an investigation of the modifications of nucleon properties inside He-3. (c) 2013 Published by Elsevier B.V