New prospects for precision correlation measurements in nuclear beta decay

Precision correlation measurements in nuclear beta decay, using atom and ion trap techniques, have made signicant progress over the past few years. Such measurements have so far been motivated by the search for possible exotic (tensor or scalar) contributions to the nuclear weak interaction as signatures of new physics beyond the standard electroweak model. This contribution addresses the potential of correlation measurements in nuclear beta decay to provide also additional inputs for the determination of the Vud element of the Cabibbo- Kobayashi-Maskawa quark mixing matrix. This matrix element has traditionally been determined from the analysis of data in nuclear superallowed 0+ ! 0+ transitions, in neutron decay and in pion beta decay but can also be independently determined from data in nuclear mirror transitions. This requires the measurement of correlation parameters in such decays to extract the Gamow- Teller to Fermi mixing ratio which dominates the error on the extracted values of jVudj