Superallowed 0+ → 0+ nuclear β decays: A new survey with precision tests of the conserved vector current hypothesis and the standard model

By J. Hardy, I. Towner. 2008

309 citations recorded by the source corpus.

A new critical survey is presented of all half-life, decay-energy, and branching-ratio measurements related to 20 superallowed ${0}^{+}\ensuremath{\rightarrow}{0}^{+}\ensuremath{\beta}$ decays. Compared with our last review, there are numerous improvements: First, we have added 27 recently published measurements and eliminated 9 references, either because they have been superseded by much more precise modern results or because there are now reasons to consider them fatally flawed; of particular importance, the new data include a number of high-precision Penning-trap measurements of decay energies. Second, we have used the recently improved isospin symmetry-breaking corrections, which were motivated by these new Penning-trap results. Third, our calculation of the statistical rate function $f$ now accounts for possible excitation in the daughter atom, a small effect but one that merits inclusion at the present level of experimental precision. Finally, we have re-examined the systematic uncertainty associated with the isospin symmetry-breaking corrections by evaluating the radial-overlap correction using Hartree-Fock radial wave functions and comparing the results with our earlier calculations, which used Saxon-Woods wave functions; the provision for systematic uncertainty has been changed as a consequence. The new ``corrected'' $\mathcal{F}t$ values are impressively constant and their average, when combined with the muon lifetime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, ${V}_{\mathit{ud}}=0.97425\ifmmode\pm\else\textpm\fi{}0.00022$. The unitarity test on the top row of the matrix becomes $|{V}_{\mathit{ud}}|{}^{2}+|{V}_{\mathit{us}}|{}^{2}+|{V}_{\mathit{ub}}|{}^{2}=0.99995\ifmmode\pm\else\textpm\fi{}0.00061$. Both ${V}_{\mathit{ud}}$ and the unitarity sum have significantly reduced uncertainties compared with our previous survey, although the new value of ${V}_{\mathit{ud}}$ is statistically consistent with the old one. From these data we also set limits on the possible existence of scalar interactions, right-hand currents, and extra $Z$ bosons. Finally, we discuss the priorities for future theoretical and experimental work with the goal of making the CKM unitarity test even more definitive.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/f08a90040164ff192c11cc6a2b41832d285e64a5

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In Nuclear and High Energy Physics

Citations in the corpus

Kaon Decays in the Standard Model (2011, background): “(4.17)], and |Vud| = 0.97425±0.00022 from superallowed nuclear β transitions (Hardy and Towner, 2009).”
Penning traps as a versatile tool for precise experiments in fundamental physics (2009, background): “lue of superallowed nuclear β- decay which connects the analog states without spin (I), parity (π), and isospin (T) change. f is a phase space integral that contains the lepton kinematics (see, e.g., [62]) and t is a partial half-life for the superallowed transition. According to the conserved vecto”
Probing Novel Scalar and Tensor Interactions from (Ultra)Cold Neutrons to the LHC (2011, methodology): “From a comparison of precisely known half-lives corrected by phase-space factors f0+→0+ , Hardy and Towner [50] found b0+ = −0.”
Solar fusion cross sections II: the pp chain and CNO cycles (2010, background): “We take (ft)0+→0+ = (3071.4 ± 0.8) s, the value for superallowed 0+ → 0+ transitions that has been determined from a comprehensive analysis of experimental rates corrected for radiative and Coulomb effects (Hardy and Towner, 2009).”