We report new shell-model calculations of the isospin-symmetry-breaking correction δ C to superallowed 0 + → 0 + nuclear β decay. The most important improvement is the inclusion of core orbitals, which are demonstrated to have a significant impact on the mismatch in the radial wave functions of the parent and daughter states. We determine which core orbitals are important to include from an examination of measured spectroscopic factors in single-nucleon pickup reactions. In addition, where new sets of effective interactions have become available since our last calculation, we now include them; this leads to small changes in δ NS as well. We also examine the new radiative-correction calculation by Marciano and Sirlin and, by a simple reorganization, show that it is possible to preserve the conventional separation into a nucleus-independent "inner" radiative term, V R , and a nucleus-dependent "outer" term, δ R . We tabulate the new values for δ C , δ NS , and δ R for 20 superallowed transitions, including the 13 currently well-studied cases. With these new correction terms, the corrected Ft values for the 13 cases are statistically consistent with one another, and the anomalousness of the 46 V result disappears. These new calculations lead to a lower average Ft value and a higher value for V ud . The sum of squares of the top-row elements of the Cabibbo-Kobayashi-Maskawa matrix now agrees exactly with unitarity.

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.

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In the past decade, one of the major challenges of particle physics has been to gain an in-depth understanding of the role of quark flavor. In this time frame, measurements and the theoretical interpretation of their results have advanced tremendously. A much broader understanding of flavor particles has been achieved; apart from their masses and quantum numbers, there now exist detailed measurements of the characteristics of their interactions allowing stringent tests of Standard Model predictions. Among the most interesting phenomena of flavor physics is the violation of the CP symmetry that has been subtle and difficult to explore. In the past, observations of CP violation were confined to neutral K mesons, but since the early 1990s, a large number of CP-violating processes have been studied in detail in neutral B mesons. In parallel, measurements of the couplings of the heavy quarks and the dynamics for their decays in large samples of K, D, and B mesons have been greatly improved in accuracy and the results are being used as probes in the search for deviations from the Standard Model. In the near future, there will be a transition from the current to a new generation of experiments; thus a review of the status of quark flavor physics is timely. This report is the result of the work of physicists attending the 5th CKM workshop, hosted by the University of Rome "La Sapienza", September 9-13, 2008. It summarizes the results of the current generation of experiments that are about to be completed and it confronts these results with the theoretical understanding of the field which has greatly improved in the past decade. (C) 2010 Elsevier B.V. All rights reserved

We have written an invited review article [1] on the determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element V ud. Data from 0 + → 0 + superallowed beta decay in nuclei, neutron decay, beta decay of odd-mass mirror nuclei and pion decay were considered. Theoretical radiative and isospin symmetry-breaking corrections were applied. The most precise result comes from the nuclear 0 + → 0 + decays, which yield a recommended value of |V ud | = 0.97425(22). We further summarized the data leading to the CKM matrix element V us : K l3 and K l2 decays, hyperon decays and hadronic tau decay. Again radiative corrections and SU(3)-symmetry breaking corrections (from lattice QCD) were applied. We adopted values from K l3 decay of |V us | = 0.2246(12) and from K l2 decay of |V us /V ud | = 0.2319(14). From the three data just cited, a least-squares fit determines two CKM matrix elements: |V ud | = 0.97425(22) and |V us | = 0.22521(94). Data leading to the third member of the top row of the CKM matrix, V ub , were summarized as well but, being of order 10-3 , that matrix element contributes negligibly to the unitarity sum, |V ud | 2 + |V us | 2 + |V ub | 2. We found this sum to be 0.99990(60), showing unitarity to be satisfied to a precision of 0.06%. We also discussed the constraints that this result places on several selected extensions to the standard model.

Superallowed 0 + → 0 + nuclear β decays: 2014 critical survey, with precise results for V ud and CKM Unitarity A new critical survey is presented of all half-life, decay-energy and branching-ratio measurements related to 20 superallowed 0 + → 0 + β decays. Included are 222 individual measurements of comparable precision obtained from 177 published references. Compared with our last review in 2008, we have added results from 24 new publications and eliminated 9 references, the results from which having been superceded by much more precise modern data. We obtain world-average f t-values for each of the eighteen transitions that have a complete set of data, then apply radiative and isospinsymmetry-breaking corrections to extract "corrected" Ft values. Fourteen of these Ft values now have a precision of order 0.1% or better. In the process of obtaining these results we carefully evaluate the available calculations of the isospin-symmetry-breaking corrections by testing the extent to which they lead to Ft values consistent with conservation of the vector current (CVC). Only one set of calculations satisfactorily meets this condition. The resultant average Ft value, when combined with the muon liftime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, V ud = 0.97417 ± 0.00021. The unitarity test on the top row of the matrix becomes |V ud | 2 + |Vus| 2 + |V ub | 2 = 0.99978 ± 0.00055 if the Particle Data Group recommended value for Vus is used. However, recent lattice QCD calculations, not included yet in the PDG evaluation, have introduced some inconsistency into kaon-decay measurements of Vus and Vus/V ud . We examine the impact of these new results on the unitarity test and conclude that there is no evidence of any statistically significant violation of unitarity. Finally, from the Ft-value data we also set limits on the possible existence of scalar interactions.

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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.