  Spin observables in radiative neutron capture on a proton and its inverse
process, photodisintegration of the deuteron are calculated using a pionless
effective field theory with di-baryon fields. Good agreement with the results
of existing standard nuclear physics approach is obtained at very low energies.
As energy increases, however, the discrepancy between the effective field
theory and the standard nuclear physics approach becomes substantial. We
discuss the origin of the difference.
