Effects of Non-nucleonic Degrees of Freedom in theD(p→,γ)H3eandp(d→,γ)H3eReactions

Measurements of the $\mathrm{D}(\overrightarrow{p},\gamma {)}^3\mathrm{He}$ and $p(\overrightarrow{d},\gamma {)}^3\mathrm{He}$ reactions below $E_{p,d}=80\mathrm{}$ keV are compared to the results of calculations based on correlated hyperspherical harmonic wave functions obtained from realistic interactions with full inclusion of Coulomb distortion in the initial continuum state, and a nuclear current operator with one- and two-body components. Dramatic effects due to the tensor force and the associated two-body (meson-exchange) interaction currents are observed in the vector and, to some extent, tensor analyzing powers for the first time. The extrapolation to zero energy leads to an S-factor value of $S(E=0\mathrm{})=0.165\mathrm{}\pm 0.014$ eV b, in reasonable agreement with theory.