Direct-reaction and isospin symmetries ind→+dreactions

We have measured angular distributions of the analyzing powers $A_y$, $A_{\mathrm{xx}}$, $A_{\mathrm{yy}}$, and $A_{\mathrm{xz}}$ for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$($\overrightarrow{d}$,$p$)${}_{}{}^3{}_{}{}^{}\mathrm{H}$ reaction at deuteron lab energies $E_d$ of 13.39 and 17.00 MeV. These distributions do not show the symmetry or antisymmetry about 90° (c.m.) expected on the basis of a simple direct-neutron-transfer reaction mechanism. In a companion experiment, we have measured the same four analyzing powers for both the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$($\overrightarrow{d}$,$p$)${}_{}{}^3{}_{}{}^{}\mathrm{H}$ reaction and its charge-symmetric partner ${}_{}{}^2{}_{}{}^{}\mathrm{H}$($\overrightarrow{d}$,$n$)${}_{}{}^3{}_{}{}^{}\mathrm{He}$ at $E_d=15.50\mathrm{} \mathrm{and} 17.00$ MeV in a restricted angular range. These latter data were obtained by simultaneously detecting the tritons and helions. Only small differences were observed in the respective analyzing powers for the two reactions, which suggests a weakening of the mechanism responsible for the larger differences found by others at lower energies.