Radiative Formation ofHe3and a New Test of Time-Reversal Invariance in the Electromagnetic Interaction

We report on the measurement of the formation of ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{++}{}_{}{}^{}$ in the collision of protons and deuterons, with the emission of a single photon. Energies and angles as chosen allow a comparison with the inverse process $\gamma {}_{}{}^3{}_{}{}^{}\mathrm{He}\to \mathrm{pd}$. These data restrict possible $T$-invariance-violation effects in the electromagnetic interaction.