High-Precision Half-Life Measurements for the Superallowed β+ Emitter C 10: Implications for Weak Scalar Currents

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Precision measurements of superallowed Fermi β-decay transitions, particularly for the lightest superallowed emitters C10 and O14, set stringent limits on possible scalar current contributions to the weak interaction. In the present work, a discrepancy between recent measurements of the C10 half-life is addressed through two high-precision half-life measurements, via γ-ray photopeak and β counting, that yield consistent results for the C10 half-life of T1/2=19.2969±0.0074 s and T1/2=19.3009±0.0017 s, respectively. The latter is the most precise superallowed β-decay half-life measurement reported to date and the first to achieve a relative precision below 10-4. A fit to the world superallowed β-decay data including the C10 half-life measurements reported here yields bF=-0.0018±0.0021 (68% C.L.) for the Fierz interference term and CS/CV=+0.0009±0.0011 for the ratio of the weak scalar to vector couplings assuming left-handed neutrinos.

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Physical Review Letters

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