Symmetry Tests in Nuclear Beta Decay

Abstract

Precision measurements in nuclear β decay provide sensitive means to test the structure of the standard electroweak model; they also allow the determination of fundamental properties in processes that involve the lightest quarks. The primary aim of such tests is to find deviations from the Standard Model predictions that may indicate new physics. We review here the status of precision measurements in nuclear β decay, including selected experiments in neutron decay, and discuss recent results and developments. Among these developments are the consideration of nuclear mirror transitions as a new window in which to test the unitarity condition of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix, measurements of angular correlation observables to search for exotic couplings, and tests of discrete symmetries.