High-precision half-life and branching-ratio measurements for superallowed Fermi β \u3csup\u3e+\u3c/sup\u3e emitters at TRIUMF - ISAC

A program of high-precision half-life and branching-ratio measurements for superallowed Fermi β emitters is being carried out at TRIUMF\u27s Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. Recent half-life measurements for the superallowed decays of 14O, 18Ne, and 26Alm, as well as branching-ratio measurements for 26Alm and 74Rb are reported. These results provide demanding tests of the Standard Model and the theoretical isospin symmetry breaking (ISB) corrections in superallowed Fermi β decays. © Owned by the authors, published by EDP Sciences, 2014

High-precision branching-ratio measurement for the superallowed Fermi β+\beta^+ emitter 18Ne

Through obseravation of the spectra of $\beta$-delayed $\gamma$-rays, the branching ratio of the superllowed Fermi transition has be determined to be (7.70(21)%) ± 2.7% precision. In this work we will determine this branching ratio for at the level of 0.2%, and significantly improve the precision on the half-life to 0.03% to establish the 18Ne ft value at a comparable level of precision to the 13 wellknown cases. This result will assess the relative accuracy of the ISB shell-structure enhancement near the N = 8 shell closure and provide important information on the validity and accuracy of recent ISB calculations

High-precision half-life measurements of the T=1/2 mirror beta decays F-17 and Cl-33

Background: Measurements of the ft values for T=1/2 mirror β+ decays offer a method to test the conserved vector current hypothesis and to determine Vud, the up-down matrix element of the Cabibbo-Kobayashi-Maskawa matrix. In most mirror decays used for these tests, uncertainties in the ft values are dominated by the uncertainties in the half-lives. Purpose: Two precision half-life measurements were performed for the T=1/2β+ emitters, 17F and 33Cl, in order to eliminate the half-life as the leading source of uncertainty in their ft values. Method: Half-lives of 17F and 33Cl were determined using β counting of implanted radioactive ion beam samples on a moving tape transport system at the Système de Production d'Ions Radioactifs Accélérés en Ligne low-energy identification station at the Grand Accélérateur National d'Ions Lourds. Results: The 17F half-life result, 64.347 (35) s, precise to ±0.05%, is a factor of 5 times more precise than the previous world average. The half-life of 33Cl was determined to be 2.5038 (22) s. The current precision of ±0.09% is nearly 2 times more precise compared to the previous world average. Conclusions: The precision achieved during the present measurements implies that the half-life no longer dominates the uncertainty of the ft values for both T=1/2 mirror decays 17F and 33Cl.status: publishe

High-precision half-life measurements of the T =1/2 mirror β\beta decays 17^{17}F and 33^{33}Cl

Expérience GANIL/SPIRALInternational audienceMeasurements of the ft values for T=1/2 mirror $\beta$+ decays offer a method to test the conserved vector current hypothesis and to determine Vud, the up-down matrix element of the Cabibbo-Kobayashi-Maskawa matrix. In most mirror decays used for these tests, uncertainties on the ft values are dominated by the uncertainties in the half-lives. Two precision half-life measurements were performed for the T=1/2 $\beta$+ emitters, 17F and 33Cl, in order to eliminate the half-life as the leading source of uncertainty in their ft values. \item[Method] Half-lives of 17F and 33Cl were determined using $\beta$ counting of implanted radioactive ion beam samples on a moving tape transport system at the SPIRAL low energy identification station at GANIL. The 17F half-life result, 64.347~(35) s, precise to $\pm$0.05 %, is a factor of 5 times more precise than the previous world average. The half-life of 33Cl was determined to be 2.5038~(22) s. The current precision of $\pm$0.09 % is nearly 2 times more precise compared to the previous world average. The precision achieved during the present measurements implies that the half-life no longer dominates the uncertainty of the ft values for both T=1/2 mirror decays 17F and 33Cl

High-precision half-life measurement for the isospin T=1/2 mirror beta(+) decay of Na-21

The half-life of the isospin T=1/2 mirror β+ decay of 21Na was measured at the GANIL-SPIRAL radioactive ion beam facility to be T1/2=22.422 (10) s, a result that is more than a factor of 5 times more precise than the previous world average, with a resulting ft value that is now two times more precise. The precision of this new result implies that the half-life is no longer the dominant source of uncertainty in the Ft value used in the calculation of Vud from mirror decays to test the conserved vector current hypothesis of the standard model. The value of Vud deduced from mirror decays using the new half-life result is now in better agreement with the Vud derived from T=1 superallowed 0+ to 0+ transitions.status: publishe

High-precision half-life measurement for the isospin T = 1/2 mirror β+\beta^+ decay of 21^{21}Na

Accepted for publication in Physical Review CInternational audienceThe half-life of the isospin T = 1/2 mirror $\beta^+$ decay of 21Na was measured at the GANIL-SPIRAL radioactive ion beam facility to be T1=2 = 22.422 (10) s, a result that is more than afactor of 5 times more precise than the previous world average, with a resulting ft value that isnow two times more precise. The precision of this new result implies that the half-life is no longerthe dominant source of uncertainty in the Ft value used in the calculation of Vud from mirrordecays to test the conserved vector current hypothesis of the Standard Model. The value of Vuddeduced from mirror decays using the new half-life result is now in better agreement with the Vudderived from T = 1 superallowed 0+ to 0+ transitions

A new FEBIAD-type ion source for the upgrade of SPIRAL1 at GANIL

GANIL/SPIRAL facility/FEBIADInternational audienceThe SPIRAL facility at GANIL is being upgraded with a new FEBIAD ion source in order to extend its productioncapabilities to condensable elements. The coupling of such an ion source with the present GANILtarget was recently tested online at SPIRAL at nominal power (1200 W). The results are promising as thecalculated yields are in the range of those extrapolated from previous measurements at lower power andsometimes higher. This experiment and its results are presented

Improved half-life determination and β-delayed γ -ray spectroscopy for 18Ne decay

The experiment was performed at the TRIUMF-ISAC radioactive ion-beam facilityThe half-life of the superallowed Fermi β + emitter 18Ne has been determined to ±0.07% precision by counting 1042 keV delayed γ rays that follow approximately 8% of all β decays. The deduced half-life, T1/2 = 1.6648 (11) s, includes a 0.7%correction that accounts for systematic losses associated with rate-dependent detector pulse pileup that was determined using a recently developed γ -ray photopeak-counting technique. This result is a factor of two times more precise than, and in excellent agreement with, a previous lower-statistics measurement that employed the same experimental setup. High-resolution β-delayed γ -ray spectroscopy results for the relative γ -ray intensities and β-decay branching ratios to excited states in the daughter 18F are also presented