Precise half-life measurement of the superallowed<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>β</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>emitter<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>38</mml:mn></mml:msup></mml:math>Ca

Park, H. I.; Hardy, J.C.; Iacob, V. E.; Banu, A.; Chen, Lie‐Wen; Golovko, V. V.; Goodwin, J.; Horvat, V.; Nica, N.; Simmons, E.; Trache, L.; Tribble, R. E.

doi:10.1103/physrevc.84.065502

Cited by 20 publications

(17 citation statements)

References 19 publications

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“…1), which includes a superallowed 0 + → 0 + branch not previously characterized. With the corresponding Q EC value [3] and half-life [4,5] already known, the transition's f t value can now be determined to ±0.2%. This is the first addition to the set of well known superallowed transitions [6] in nearly a decade and, being from a T Z = −1 parent nucleus, it provides the opportunity to make a high-precision comparison of the f t values from a pair of mirror superallowed decays, 38 Ca → 38m K and 38m K → 38 Ar.…”

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confidence: 99%

“…This nuclide is not present in the beam, but it naturally grows in the collected sample as the 38 Ca decays. Since the half-lives of 38 Ca and 38m K are well known [4][5][6], the ratio of their activities could be accurately calculated, based on the measured time dependence of the 38 Ca deposit rate. We determined that the betas from 38 Ca constituted 35.10(2)% of the combined betas from 38 Ca and 38m K. Finally, a Monte-Carlo-calculated correction factor of 0.99957(4) was applied to account for 38 Ca γ-rays being detected in the thin β-detector.…”

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confidence: 99%

“…The half-life of 38 Ca is 443.77(35) ms [4,5] and the Q EC value for its superallowed branch is 6612.12 (7) keV [3]. Taking these results with our new value for the branching ratio and correcting for electron capture, we arrive at an f t value for the 38 Ca superallowed branch of f t a = 3062.3(68) s. The f t value for the mirror transition from 38m K is f t b = 3051.5(9) s, a value that comes from the 2009 survey [6] updated for a more recent Q EC measurement reported by Eronen et al [15].…”

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confidence: 99%

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The β Decay of ³⁸Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0⁺ → 0⁺ Transitions

Park¹,

Hardy²,

Iacob³

et al. 2015

Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014)

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We report the first branching-ratio measurement of the superallowed 0 + → 0 + β-transition from 38 Ca. The result, 0.7728(16), leads to an f t value of 3062.3(68)s with a relative precision of ±0.2%. This makes possible a high-precision comparison of the f t values for the mirror superallowed transitions, 38 Ca → 38m K and 38m K → 38 Ar, which sensitively tests the isospin symmetry-breaking corrections required to extract V ud , the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, from superallowed β decay. The result supports the corrections currently used, and points the way to even tighter constraints on CKM unitarity.

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The β Decay of ³⁸Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0⁺ → 0⁺ Transitions

Park¹,

Hardy²,

Iacob³

et al. 2015

Proceedings of the Conference on Advances in Radioactive Isotope Science (ARIS2014)

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“…We have already published our half-life results for the first three of these cases [7][8][9] and now have measured the branching ratio for the 38 Ca decay [3], the last link required to complete the A = 38 mirror pair.…”

Section: Measurement Of the 38 Ca Branching Ratiomentioning

confidence: 99%

Testing CVC and CKM Unitarity via superallowed nuclear beta decay

Hardy

Towner

Park

et al. 2015

EPJ Web of Conferences

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Abstract. Currently, the most restrictive test of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is anchored by nuclear beta decay. Precise measurements of the f t-values for superallowed beta transitions between analog 0 + states are used to determine G V , the vector coupling constant; this, in turn, yields V ud , the up-down quark-mixing element of the CKM matrix. The determination of a transition's f t-value requires the measurement of three quantities: its Q value, branching ratio and parent half-life. To achieve 0.1% precision on the final result, each of these quantities must be measured to substantially better precision, for which special techniques have had to be developed. A new survey and analysis of world data reveals that there are now fourteen such transitions with f t-values known to ∼ 0.1% precision or better, and that they span a wide range of nuclear masses, from 10 C, the lightest parent, to 74 Rb, the heaviest. Of particular interest is the recent completion of the first mirror pair of 0 + → 0 + transitions, 38 Ca → 38m K and 38m K → 38 Ar, which provides a valuable constraint on the calculated isospin-symmetry-breaking corrections needed to derive G V from the experimental data. As anticipated by the Conserved Vector Current hypothesis, CVC, all fourteen transitions yield consistent values for G V . The value of V ud derived from their average makes it by far the most precisely known element of the CKM matrix, which, when combined with the other top-row elements, V us and V ub , leads to the most demanding test available of the unitarity of that matrix. Since CKM unitarity is a key pillar of the Electroweak Standard Model, this test is of fundamental significance.

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“…This nuclide is not present in the implanted beam, but it naturally grows in the collected sample as the 38 Ca decays. Since the half-lives of 38 Ca and 38m K are well known [1,16,17], the ratio of their activities can easily be calculated if the 38 Ca implantation rate is known as a function of time during the collection period [17]. To enable this calculation, we recorded the time profile of ions detected by the scintillator at the exit of MARS for each individual cycle.…”

Section: Parent β-Decay Fractionmentioning

confidence: 99%

Precise measurement of branching ratios in theβdecay ofCa38

et al. 2015

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We present the full description of a measurement of the branching ratios for the β-decay of 38 Ca. This decay includes five allowed 0 + → 1 + branches and a superallowed 0 + → 0 + one. With our new result for the latter, we determine its f t value to be 3062.3±6.8 s, a result whose precision (0.2%) is comparable to the precision of the thirteen well known 0 + → 0 + transitions used up till now for the determination of V ud , the up-down quark-mixing element of the CKM matrix. The 38 Ca superallowed transition thus becomes the first addition to this set of transitions in nearly a decade and the first for which a precise mirror comparison is possible, thus enabling an improved test of the isospin-symmetry-breaking corrections required for the extraction of V ud .

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Precise half-life measurement of the superallowedβ+emitter38Ca

Cited by 20 publications

References 19 publications

The β Decay of ³⁸Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0⁺ → 0⁺ Transitions

The β Decay of ³⁸Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0⁺ → 0⁺ Transitions

Testing CVC and CKM Unitarity via superallowed nuclear beta decay

Precise measurement of branching ratios in theβdecay ofCa38

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Precise half-life measurement of the superallowedβ+emitter38Ca

Cited by 20 publications

References 19 publications

The β Decay of 38Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0+ → 0+ Transitions

The β Decay of 38Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0+ → 0+ Transitions

Testing CVC and CKM Unitarity via superallowed nuclear beta decay

Precise measurement of branching ratios in theβdecay ofCa38

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The β Decay of ³⁸Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0⁺ → 0⁺ Transitions

The β Decay of ³⁸Ca: Sensitive Test of Isospin Symmetry-Breaking Corrections from Mirror Superallowed 0⁺ → 0⁺ Transitions