Precision determination of Q-values relevant to superallowed nuclear β-decay

Vonach, H.; Glässel, P.; Huenges, Ernst; Maier-Komor, P.; Rösler, H.; Scheerer, Herbert; Paul, H.; Semrad, D.

doi:10.1016/0375-9474(77)90234-2

Cited by 69 publications

(56 citation statements)

References 13 publications

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“…The result differed significantly from the previously accepted result -a longstanding reaction-based Q EC value published in 1977 [3] -and shifted the 46 V f t value two standard deviations out of agreement with other well-known superal- * hpark@comp.tamu.edu † hardy@comp.tamu.edu lowed transitions. This apparent deviation from the conserved vector current (CVC) expectation raised several concerns, among them the possibility of systematic differences between reaction and Penning-trap measurements of Q values.…”

contrasting

confidence: 56%

“…At the same time though, the Q EC -value results for 26 Al m and 42 Sc were consistent with previous reaction-based values, thus demonstrating that there were no widespread systematic effects afflicting all reaction-based measurements. Evidently, the problem with the 46 V Q EC value arose from some flaw specific to one particular set of reaction measurements [3]. This conclusion was further strengthened by a subsequent Q-value measurement in 2009 [5], which used the same ( 3 He, t) reaction and some of the same equipment as had been used 32 years earlier in the flawed measurement.…”

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confidence: 78%

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Precise half-life measurement of the superallowedβ+emitter46V

et al. 2012

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The half-life of 46 V has been measured to be 422.66(6) ms, which is a factor of two more precise than the best previous measurement. Our result is also consistent with the previous measurements, with no repeat of the disagreement recently encountered with QEC values measured for the same transition. The Ft value for the 46 V superallowed transition, incorporating all world data, is determined to be 3074.1(26) s, a result consistent with the average Ft value of 3072.08(79) s established from the 13 best-known superallowed transitions.

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confidence: 56%

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confidence: 78%

Precise half-life measurement of the superallowedβ+emitter46V

et al. 2012

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“…If, as seems likely, the problem with the 46 V measurement in Ref. [48] is not limited to that measurement alone, then doubt is certainly cast on the 50 Mn and 54 Co Q ECvalue results quoted in that reference as well. New Penningtrap measurements of both Q EC values are currently in progress [50], and the question should be settled shortly.…”

Section: F T Values V Ud and Ckm Unitaritymentioning

confidence: 99%

“…Rather than being a negative result, however, this possible discrepancy offers us the opportunity to use the cases of 50 Mn and 54 Co as a valuable test of our improved calculations. The Q EC value for each of them has been measured only twice with (claimed) high precision [48,49], and one of these references [48] also included a measurement of the Q EC value for 46 V, which Penning-trap measurements have recently shown [6,7] to be low by 2 keV-more than three times its originally quoted standard deviation. If, as seems likely, the problem with the 46 V measurement in Ref.…”

Section: F T Values V Ud and Ckm Unitaritymentioning

confidence: 99%

Improved calculation of the isospin-symmetry-breaking corrections to superallowed Fermi β decay

2008

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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.

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“…Our decision to do so deserves a more detailed explanation. In 1977, Vonach et al published in a single paper [162] the Q EC values for seven superallowed emitters ( 14 O, 26 Al m , 34 Cl, 42 Sc, 46 V, 50 Mn, and 54 Co), which they had determined from the Q values for ( 3 He,t) reactions on their stable daughters. They had used a "precision time-of-flight measuring system" with the Q3D spectrograph of the Munich Tandem Laboratory to produce uncertainties of 0.4-0.6 keV.…”

Section: A Evaluation Principlesmentioning

confidence: 99%

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

2009

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A new critical survey is presented of all half-life, decay-energy, and branching-ratio measurements related to 20 superallowed 0 + → 0 + β 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" Ft 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 ud = 0.97425 ± 0.00022. The unitarity test on the top row of the matrix becomes |V ud | 2 + |V us | 2 + |V ub | 2 = 0.99995 ± 0.00061. Both V ud and the unitarity sum have significantly reduced uncertainties compared with our previous survey, although the new value of V 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.

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Precision determination of Q-values relevant to superallowed nuclear β-decay

Cited by 69 publications

References 13 publications

Precise half-life measurement of the superallowedβ+emitter46V

Precise half-life measurement of the superallowedβ+emitter46V

Improved calculation of the isospin-symmetry-breaking corrections to superallowed Fermi β decay

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

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