Measurement of the half-life of 20F

Wang, T.F.; Boyd, R. N.; Mathews, G. J.; Roberts, M.L.; Sale, K.E.; Farrell, Molly; Islam, M. S.; Kolnicki, G.W.

doi:10.1016/0375-9474(92)90251-e

Cited by 6 publications

(16 citation statements)

References 3 publications

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Section: Discussioncontrasting

confidence: 65%

“…The long standing discrepancy in the half-life of 20 F has been known for over 30 years [11]. The result from this work disagrees with two of the precision measurements from the past [5,11], while affirming the validity of the high precision measurement reported more recently [10]. The new world average including this work is 11.0062(80) s. A consistent set of measurements has been determined by only considering results which utilized maximum likelihood fitting.…”

Section: Discussionmentioning

confidence: 49%

“…1. The most recent measurement [10] conflicts with previous measurements of comparable precision [5,11], while agreeing with three lower precision measurements [7,12,13]. This provides a strong incentive to repeat the measurement with a different apparatus that has different inherent systematic uncertainties.…”

Section: Introductionmentioning

confidence: 48%

“…9. It should be noted that two precise measurements [5,11] discrepant with the new world average by more than 13 σ have been removed. The article of the 1976 measurement [5] mentioned that a least-square fitting procedure was used to analyze the data and a private communication with one of the authors of the 1992 measurement [11] also revealed use of the same technique [34].…”

Section: F Half-lifementioning

confidence: 99%

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Resolving the discrepancy in the half-life of F20

et al. 2019

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Section: Discussioncontrasting

confidence: 65%

Section: Discussionmentioning

confidence: 49%

Section: Introductionmentioning

confidence: 48%

Section: F Half-lifementioning

confidence: 99%

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Resolving the discrepancy in the half-life of F20

et al. 2019

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“…using logf t 20 ( 20 F) = 4.9753 ± 0.0007 s [37][38][39] and logf t 20 ( 20 Na) = 4.990 ± 0.005 s [40,41]. The difference of f t values of about 3% between 20 F and 20 Na was quoted as an error to the logf t 20 .…”

Section: E β-γ Angular Correlation Experimentsmentioning

confidence: 98%

Low-energy test of second-class current inβdecays of spin-aligned20F and20Na

et al. 2011

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The G-parity-violating, second-class current-(SCC) induced tensor term in the weak-nucleon axial-vector current was determined from β-decay correlation measurements of the mass A = 20 mirror pair. The alignment correlation terms in the β-decay angular distribution from the purely spin aligned mirror pair, 20 F and 20 Na, were measured in the present study. Combining the present results with existing results of β and delayed γ -ray angular correlation measurements for the A = 20 mirror pair, the SCC-induced tensor term was extracted to be d II /Ac = 0.18 ± 0.48. In the extraction, the weak-magnetism term, b/Ac = 8.58 ± 0.28, evaluated from the M1 analog γ -ray decay strength, was used in a framework of the conserved vector current hypothesis. This is the first unambiguous extraction of the (b − d II )/Ac term free from the contribution of the second-forbidden form factor, j 2 , in the axial-vector current, which was a limiting factor for accurate determination of nonexistence of the SSC in the β decay of the A = 20 system. K. MINAMISONO et al. PHYSICAL REVIEW C 84, 055501 (2011) cancellations [5,10], possibly due to uncertainties in the nuclear structure. Therefore, the search for violation should be undertaken in various mass systems. For this purpose, β-decay correlation measurements were performed in the A = 8 (β-α angular correlation) [11,12] and A = 20 (β-γ angular correlation) [13-17] mirror systems. The β-decay correlation terms were formulated to first order of recoil terms in Ref. [7] and expressions taken in the reference will be used hereafter in this article. Unambiguous extraction of SCC from those correlation measurements, however, has been rather difficult due to imperfect knowledge of the M1/E2 mixing ratio of M1 analog γ decays and poor statistical error of the γ -ray decay strengths, from which a second-forbidden form factor, f , in the vector current is evaluated under an assumption of CVC.An alternative procedure to extract the SCC-induced tensor term was recently introduced in the A = 8 system [18], where the alignment correlation terms in the β-decay angular distribution from nuclear-spin aligned 8 Li and 8 B were combined with the β-α angular correlation terms. The (b − d II )/Ac term and other coupling constants associated with higherorder matrices are independently determined by fitting both correlation terms simultaneously. Here b/Ac is the weak magnetism, d II /Ac is the SCC-induced tensor term with c being Gamow-Teller form factor and g T /g A = d II /Ac. This procedure, combining both correlation terms, is a more reliable way to extract the (b − d II )/Ac term than that with a single correlation measurement. It is noted that the SCC-induced tensor term always appears with the weak magnetism in those correlation type measurements, and therefore, precise extraction of the SCC-induced tensor term is possible only when the weak magnetism is well known.The alignment correlation terms of the A = 20 system, 20 F(I π = 2 + , T 1/2 = 11.07 s) and 20 Na(I π = 2 + , T 1/2 = 447.9 ms), were m...

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