Experimental Test of Time-Reversal Invariance in the Reactionn+p→γ+d

A measurement of the angular distribution for the reaction $n+p\to \gamma +d$ has been made at the Lawrence Radiation Laboratory 184-in. cyclotron for neutron kinetic energies in range 300 to 720 MeV. A total of 30 000 $n+p\to \gamma +d$ events were collected in twenty energy-angle bins. A comparison with the angular distribution for the inverse process indicates that the data are consistent with time-reversal invariance in this reaction. If the results are interpreted in the framework of a model by Barshay, the measured $T$-invariance violating phase angle is $\varphi ={(4\mathrm{}\pm 10)}^{\circ }$, where $\varphi ={90}^{\circ }$ for a maximal $T$-invariance violation.