Measurements of the Absolute Cross Section of the Three-body Photodisintegration of Helium-3 Between E[gamma] = 11.4 MeV and 14.7 MeV at HIGS

Abstract

Measurements of the three-body photodisintegration of 3He were performed at the High Intensity &gamma-ray Source (HI&gammaS). Neutrons emitted in this reaction inside a 3He gas target were detected with seven 12.7 cm diameter liquid scintillator detectors. Time-of-flight (TOF) and pulse-shape discrimination (PSD) techniques were used to identify neutron events. The absolute differential cross sections for the 3He(&gamma, n)pp reaction as a function of outgoing neutron scattering angle and energy were determined from the measurements at the incident &gamma-ray energies of 11.4, 12.8, 13.5, and 14.7 MeV to within a precision better than +/- 6 %.The absolute cross sections at each incident energy are compared to the results of Gorbunov [Gor74], phase space calculations, and state-of-the-art three-body calculations. The inclusion of the Coulomb interaction in the three-body problem has been a long-standing challenge in theoretical nuclear physics. The present experimental data were found to be in good agreement with the state-of-the-art theory, which includes a full treatment of the Coulomb interaction betweenthe protons in the final state [Del05].