3H-p-vector,γ)4He reaction below Ep=80 keV

The 3H-p-vector,γ)4He reaction was studied at incident energies of Ep=40 and 80 keV at the Triangle Universities Nuclear Laboratory (TUNL) using beams from a polarized ion source. The present study was the logical progression of a previous study of the 2H(p-vector,γ)3He reaction done by the radiative capture group at TUNL. The angular distributions of the cross section, σ(θ), and the analyzing power, Ay(θ), were measured at incident proton beam energies of 40 keV and 80 keV. In both cases the beam was stopped in the target. The magnetic dipole transition strength was determined from the results of a TME analysis. A comparison of the M1 strength with that seen in similar reactions in the three-nucleon case made it possible to infer the meson-exchange current origin of most of this strength. Previous measurements of the absolute cross section extended down to beam energies of 100 keV. The present study extends the measured cross section data to lower energies and is consistent with the previous results. A parametrization of the astrophysical S factor including both data sets was performed