  Pionless effective field theory with dibaryon fields is reexamined for
observables involving the deuteron. The electromagnetic form factors of the
deuteron and the total cross sections of radiative neutron capture on the
proton, $np \to d\gamma$, are calculated. The low energy constants of
vector(photon)-dibaryon-dibaryon vertices in the effective lagrangian are fixed
primarily by the one-body vector(photon)-nucleon-nucleon interactions. This
scheme for fixing the values of the low energy constants satisfactorily
reproduces the results of the effective range theory. We also show that, by
including higher order corrections, one can obtain results that are close to
those of Argonne v18 potential model.
