Differential cross sections for $\mathrm{d}+\mathrm{d}\to {}_{}{}^4{}_{}{}^{}\mathrm{He}+\gamma$ have been measured at ${\theta }_{\gamma }(\mathrm{c}.\mathrm{m}.)=73\mathrm{}° \mathrm{and} 91°$ for $T_{\mathrm{d}}=376\mathrm{}$ MeV. Our results are a factor of 60 smaller than the cross section measured at $T_{\mathrm{d}}=404\mathrm{}$ MeV by Akimov et al. The ratios of our results to those of Arends et al. for the inverse reaction, $\gamma {}_{}{}^4{}_{}{}^{}\mathrm{He}\to \mathrm{dd}$, are 2.0±0.9 at 73° and 1.7±0.9 at 91°. Considering the large uncertainties in both data sets, these ratios are consistent with time-reversal invariance in this isoscalar electromagnetic interaction of hadrons. Our data corroborate the reported deviation from the ${sin}^{2}2\theta$ angular distribution expected of this reaction.

[NUCLEAR REACTIONS ${}_{}{}^2{}_{}{}^{}\mathrm{H}(\mathrm{d},\gamma ){}_{}{}^4{}_{}{}^{}\mathrm{He}$, $T_{\mathrm{d}}=376\mathrm{}$ MeV; measured $\sigma \left(\theta \right)$, $\theta \mathrm{}(\mathrm{c}.\mathrm{m}.\mathrm{})\mathrm{}=73\mathrm{}°,91\mathrm{}°$.]

• Received 30 December 1982

DOI:https://doi.org/10.1103/PhysRevC.29.35