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

Precision measurements of superallowed Fermi β -decay transitions, particularly for the lightest superallowed emitters ¹⁰C and ¹⁴O, set stringent limits on possible scalar current contributions to the weak interaction. In the present work, a discrepancy between recent measurements of the ¹⁰C half-life is addressed through two high-precision half-life measurements, via γ -ray photopeak and β counting, that yield consistent results for the ¹⁰C half-life of T_{1 /2}=19.2969 ±0.0074 s and T_{1 /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 ¹⁰C half-life measurements reported here yields b_F=-0.0018 ±0.0021 (68% C.L.) for the Fierz interference term and C_S/C_V=+0.0009 ±0.0011 for the ratio of the weak scalar to vector couplings assuming left-handed neutrinos.