Absolute Cross Section for Neutron-Proton Radiative Capture atTn=185MeV

The differential cross section for the reaction $p\mathrm{}(n,d)\mathrm{}\gamma$ has been measured for angles between ${\theta }_d=0\mathrm{}°$ and ${\theta }_d(\mathrm{c}.\mathrm{m}.\mathrm{})=65\mathrm{}°$ at a neutron kinetic energy $T_n=185\mathrm{}$ MeV. On the assumption of time-reversal invariance, our results are in agreement with the deuteron photo-disintegration measurement at ${\theta }_p=0\mathrm{}°$ performed by Hughes et al. at Mainz. At present there exists no calculation for this reaction which is in satisfactory agreement with our measurements. The disparity between theory and experiment in this basic process, therefore, poses a persisting problem.