  The cross section for n+p -> d+gamma is calculated at energies relevant to
big bang nucleosynthesis using the recently developed effective field theory
that describes the two-nucleon sector. The E1 amplitude is computed up to NNNLO
and depends only upon nucleon-nucleon phase shift data. In contrast, the M1
contribution is computed up to NLO, and the four-nucleon-one-magnetic-photon
counterterm that enters is determined by the cross section for cold neutron
capture. The uncertainty in the calculation for nucleon energies up to E ~ 1
MeV is estimated to be < 4%.
