Superallowed0+→0+nuclearβdecays: A critical survey with tests of the conserved vector current hypothesis and the

Abstract

A complete and critical survey is presented of all half-life, decay-energy and branching-ratio measurements related to 20 superallowed 0 + → 0 + decays; no measurements are ignored, though some are rejected for cause and others updated. A new calculation of the statistical rate function f is described and experimental f t values determined. The associated theoretical corrections needed to convert these results into Ft values are discussed, and careful attention is paid to the origin and magnitude of their uncertainties. As an exacting confirmation of the conserved vector current hypothesis, the Ft values are seen to be constant to 3 parts in 10 4 . These data are also used to set a new limit on any possible scalar interaction: C S /C V = −(0.00005 ± 0.00130). The average Ft value obtained from the survey, when combined with the muon liftime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa matrix, V ud = 0.9738 ± 0.0004; and the unitarity test on the top row of the matrix becomes |V ud | 2 + |V us | 2 + |V ub | 2 = 0.9966 ± 0.0014 using the Particle Data Group's currently recommended values for V us and V ub . We also express this result in terms of the possible existence of right-hand currents. Finally, we discuss the priorities for future theoretical and experimental work with the goal of making the CKM unitarity test more definitive.

Supersymmetric contributions to weak decay correlation coefficients

“…Coefficients of this magnitude could, in principle, be probed with a new generation of precision -decay correlation studies. At present, the most precise tests of these quantities arises from superallowed Fermi nuclear -decay, from which one obtains constraints on the Fierz interference coefficient b F 0:0026 26 [47,48]. For this transition one has independent of the details of the nuclear matrix elements.…”

AnalogE1transitions and isospin mixing

“…Isospin mixing and its effect on beta-decay matrix elements is of considerable interest in the context of tests of the Conserved Vector Current hypothesis [6]. Such tests concern the beta decay of Fermi superallowed emitters for which the log f t value should have a fixed value if the CVC hypothesis is correct.…”

Precision mass measurements of short-lived nuclides for nuclear structure studies at TITAN

“…Accurate and precise mass values of atomic nuclides are important for many disciplines in physics including the study of nuclear structure [1], the study of the production of elements in stellar nucleosynthesis [2], and the test of fundamental symmetries, such as the conserved vector current (CVC) hypothesis in super allowed β decays [3]. However, the required relative uncertainty of the mass depends on the physics under investigation and generally varies from δm/m = 10 −6 to 10 −11 [4].…”