The contribution of the (3)(H)over-right-arrowe((gamma)over-right-arrow, n)pp reaction to the GDH integrand below pion production threshold

The first measurements of the three-body phototdisintegration of He-3 polarized parallel and anti-parallel to a circularly polarized gamma-ray beam were carried out at the High Intensity gamma-ray Source (HI gamma S) facility located at Triangle Universities Nuclear Laboratory (TUNL). A high pressure He-3 target, polarized via spin-exchange optical pumping with alkali metals, was used in the experiments. The neutrons from the three-body photodisintegration were detected with sixteen 12.7 cm diameter liquid scintillator detectors. The spin-dependent cross sections and the contributions from the three-body photodisintegration to the He-3 Gerasimov-Drell-Hearn sum rule integrand were extracted and compared with state-of-the-art three-body calculations at the incident photon energies of 12.8, 14.7, and 16.5 MeV. The calculations, which include the Coulomb interaction are in good agreement with the results of the measurements at 12.8 and 14.7 MeV but deviate from the results at 16.5 MeV.