In interpreting the SNO experiments, accurate estimates of the νd reaction cross sections are of great importance. We improve the previous estimates of our group by updating some of its inputs and by taking into account the results of a recent effective-field-theoretical calculation. The new cross sections are slightly (∼1 %) larger than the previously reported values. It is shown to be reasonable to assign 1% uncertainty to the νd cross sections reported here; this error estimate does not include radiative corrections, for which we refer to the literature. : 25.30.Pt, 25.10.+s, 26.65.+t, 95.30.Cq
PACS
Radiative corrections to the lifetime and angular correlation coefficients of neutron beta-decay are evaluated in effective field theory. We also evaluate the lowest order nucleon recoil corrections, including weak-magnetism. Our results agree with those of the long-range and model-independent part of previous calculations. In an effective theory the model-dependent radiative corrections are replaced by well-defined low-energy constants. The effective field theory allows a systematic evaluation of higher order corrections to our results to the extent that the relevant low-energy constants are known.
The total cross section for radiative neutron capture on a proton, np → dγ , is evaluated at big-bang nucleosynthesis (BBN) energies. The electromagnetic transition amplitudes are calculated up to next-to-leadingorder within the framework of pionless effective field theory with dibaryon fields. We also calculate the dγ → np cross section and the photon analyzing power for the d γ → np process from the amplitudes. The values of low-energy constants that appear in the amplitudes are estimated by a Markov Chain Monte Carlo analysis using the relevant low-energy experimental data. Our result agrees well with those of other theoretical calculations except for the np → dγ cross section at some energies estimated by an R-matrix analysis. We also study the uncertainties in our estimation of the np → dγ cross section at relevant BBN energies and find that the estimated cross section is reliable to within ∼1% error.
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