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 cross sections for the ν−d andν−d reactions are calculated for the incident energy up to E ν = 170 MeV, with the use of a phenomenological Lagrangian approach. We assess and improve the reliability of the employed calculational method by examining the dependence of the results on various input and approximations that go into the calculation. The main points of improvements over the existing work are: (1) use of the "modern" NN potentials;(2) use of the more accurate nucleon weak-interaction form factors; (3) monitoring the strength of a vertex that governs the exchange-current contribution, with the use of data on the related process, n + p → d + γ. In addition to the total cross sections, we present various differential cross sections that are expected to be useful for the SNO and other experiments.In the low energy regime relevant to the solar neutrinos, the newly calculated total cross sections essentially agree with the existing literature values. The origins of slight differences found for higher energies are discussed. The ratio between the neutral-current and chargedcurrent reaction cross sections is found to be extremely stable against any variations in the input of our calculation.

A general analysis of the sensitivities of neutron β-decay experiments to manifestations of possible interaction beyond the standard model is carried out. In a consistent fashion, we take into account all known radiative and recoil corrections arising in the standard model. This provides a description of angular correlations in neutron decay in terms of one parameter, which is accurate to the level of ∼10 −5 . Based on this general expression, we present an analysis of the sensitivities to new physics for selected neutron decay experiments. We emphasize that the usual parametrization of experiments in terms of the tree-level coefficients a, A, and B is inadequate when the experimental sensitivities are at the same or higher level relative to the size of the corrections to the tree-level description.

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