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Register a new userHigh-Precision Measurement of the 19Ne Half-Life and Implications for Right-Handed Weak Currents
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We report a precise determination of the 19Ne half-life to be $T_{1/2} = 17.262 pm 0.007$ s. This result disagrees with the most recent precision measurements and is important for placing bounds on predicted right-handed interactions that are absent in the current Standard Model. We are able to identify and disentangle two competing systematic effects that influence the accuracy of such measurements. Our findings prompt a reassessment of results from previous high-precision lifetime measurements that used similar equipment and methods.
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The beta-decay half-life of 62Ga has been studied with high precision using on-line mass separated samples. The decay of 62Ga which is dominated by a 0+ to 0+ transition to the ground state of 62Zn yields a half-life of T_{1/2} = 116.19(4) ms. This result is more precise than any previous measurement by about a factor of four or more. The present value is in agreement with older literature values, but slightly disagrees with a recent measurement. We determine an error weighted average value of all experimental half-lives of 116.18(4) ms.
Studies of 6He beta decay along with tritium can play an important role in testing ab-initio nuclear wave-function calculations and may allow for fixing low-energy constants in effective field theories. Here, we present an improved determination of the 6He half-life to a relative precision of 3x10^(-4). Our value of 806.89 pm 0.11(stat)^{+0.23}_{-0.19}(syst) ms resolves a major discrepancy between previous measurements. Calculating the statistical rate function we determined the ft-value to be 803.04 ^{+0.26}_{-0.23} s. The extracted Gamow-Teller matrix element agrees within a few percent with ab-initio calculations.
A high-precision half-life measurement for the superallowed Fermi $beta^+$ emitter $^{22}$Mg was performed at the TRIUMF-ISAC facility using a 4$pi$ proportional gas counter. The result of $T_{1/2} = 3.87400 pm 0.00079$ s is a factor of 3 more precise than the previously adopted world average and resolves a discrepancy between the two previously published $^{22}$Mg half-life measurements.
The half-life of $^{19}$Ne has been measured using a real-time digital multiparametric acquisition system providing an accurate time-stamp and relevant information on the detectors signals for each decay event. An exhaustive offline analysis of the data gave unique access to experimental effects potentially biasing the measurement. After establishing the influence factors impacting the measurement such as after-pulses, pile-up, gain and base line fluctuations, their effects were accurately estimated and the event selection optimized. The resulting half-life, $17.2569pm0.0019_{(stat)}pm0.0009_{(syst)}$~s, is the most precise up to now for $^{19}$Ne. It is found in agreement with two recent precise measurements and not consistent with the most recent one [L.J. Broussard {it et al.}, Phys. Rev. Lett. {bf112}, 212301 (2014)] by 3.0 standard deviations. The full potential of the technique for nuclei with half-lives of a few seconds is discussed.
The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the $^{92}$Mo($alpha$,n)$^{95}$Ru reaction was measured recently using this experimental approach. The preliminary results indicated that the literature half-life of $^{95}$Ru, derived about half a century ago, is overestimated. Therefore, the half-lives of $^{95}$Ru and its daughter isotope $^{95}$Tc and $^{95m}$Tc have been measured with high precision using $gamma$-spectroscopy. The results are t$_{1/2}$=1.6033 $pm$ 0.0044 h for $^{95}$Ru, t$_{1/2}$ = 19.258 $pm$ 0.026 h for $^{95}$Tc and t$_{1/2}$ = 61.96 $pm$ 0.24 d for $^{95m}$Tc. The precision of the half-life values has been increased, consequently the recently measured $^{92}$Mo($alpha$,n)$^{95}$Ru activation cross section will become more precise.
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