The measurement and interpretation of superallowed 0+→ 0+ nuclear β decay
Measurements of the decay strength of superallowed 0+? 0+ nuclear ? transitions shed light on the fundamental properties of weak interactions. Because of their impact, such measurements were first reported 60?years ago in the early 1950s and have continued unabated ever since, always taking advantage of improvements in experimental techniques to achieve ever higher precision. The results helped first to shape the Electroweak Standard Model but more recently have evolved into sensitively testing that model's predictions. Today they provide the most demanding test of vector-current conservation and of the unitarity of the Cabibbo?Kobayashi?Maskawa matrix, as well as the most restrictive limit on the presence of a scalar current. Here, we review the experimental and theoretical methods that have been, and are being, used to characterize superallowed 0+? 0+ ? transitions and to extract fundamentally important parameters from their analysis.