Tensor-force effects in theH2(d→,γ)4He reaction and theDstate ofHe4

Vector analyzing powers, tensor analyzing powers, and relative differential cross sections have been measured for the ${}_{}{}^2{}_{}{}^{}(\mathrm{d}\to$,γ${)\mathrm{}}^4$He reaction at an incident energy of 10 MeV. Multipole decomposition and partial-wave analysis reveal that about 15% of the cross section involves processes in which the tensor force plays a role, either in the entrance or exit channel. Contrary to earlier claims, the reaction cannot be used to determine the D-state admixture in the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ wave function unless the D state of the deuteron and other tensor-force effects in the entrance channel are taken into account.