The H-2((p)over-right-arrow,gamma)He-3 and H-1((d)over-right-arrow,gamma)He-3 reactions below 80 keV

The details of a recent experimental study of the H-2((p) over right arrow, gamma)He-3 and the H-1((d) over right arrow,gamma)He-3 reactions for beam energies below 80 keV are discussed. In this study, both polarized and unpolarized incident beams were used to measure the cross section sigma(theta,E), the astrophysical S factor S(theta,E), the vector analyzing power A,(theta,E), and the tensor analyzing power T-20(theta). In addition, the gamma-ray linear polarization P-gamma(theta) was measured for an unpolarized incident beam. The experimental details of these measurements are discussed and the data are analyzed to obtain the amplitudes and phases of the contributing transition-matrix elements. The results of our measurements are compared with recent ab initio three-body theoretical calculations. This comparison reveals the large sensitivity of the polarization observables, especially the vector analyzing power (A(y)), to the presence of meson-exchange current effects and indicates the need for further study. The tensor analyzing power data [T-20(theta)] an used to extract a value of the asymptotic D- to S-state ratio, eta, for He-3.