He at TUNL*

The first exclusive low enegy cross-section measurements for three-body photodisintegration of ³He have been performed using the nearly monoenergetic photon beam at the High Intensity γ-ray Source (HIγS) facility at Triangle Universities Nuclear Laboratory.  These data test ab-initio calculations using a combination of absolute and relative measurements across a broad range of three-nucleon phase space.

The initial focus of the measurements and data analysis is on the neutron-proton (np) 1S0 final-state-interaction. The 1S0 np scattering length, a_np, is well known from two-nucleon scattering measurements, so determination of this parameter in the ³He photodisintegration reaction allows for investigation of the theoretical treatment of three-nucleon interaction, meson-exchange currents, and the Coulomb interaction in rigorous three-nucleon calculations.  A discussion of the methods employed and preliminary results will be presented.