Eur. Phys. J. A 15, 223-227 (2002)
DOI: 10.1140/epja/i2001-10258-0

Superallowed beta-decay and CKM unitarity

Recent results and future prospects

J.C. Hardy¹ and I.S. Towner<sup>2

1</sup>  Cyclotron Institute, Texas A & M University, College Station, TX 77843, USA
²  Physics Department, Queen's University, Kingston, Ontario K7L 3N6, Canada

hardy@comp.tamu.edu

(Received: 21 March 2002 / Published online: 31 October 2002)

Abstract
Precise measurements of the ft-values for superallowed nuclear -decay yield results that support conservation of the weak vector current but violate the unitarity of the Cabibbo-Kobayashi-Maskawa matrix by more than two standard deviations. This apparent violation of the Standard Model has led to considerable theoretical and experimental activity largely focussed on reducing uncertainties in the small correction terms that account for charge-dependent nuclear effects. This activity is outlined and the prospects for future sharpening of the unitarity test are assessed.

PACS
23.40.Bw - Weak-interaction and lepton (including neutrino) aspects.
23.40.Hc - Relation with nuclear matrix elements and nuclear structure.

© Società Italiana di Fisica, Springer-Verlag 2002