We have omitted some results that have been superseded by later experiments. See our earlier editions. Anyone interested in the neutron should look at these two review articles: D. Dubbers and M.G. Schmidt, “The neutron and its role in cosmology and particle physics,” Reviews of Modern Physics 83 1111 (2011); and F.E. Wietfeldt and G.L. Greene, “The neutron lifetime,” Reviews of Modern Physics 83 1173 (2011).