Two complementary experimental techniques have been used to extract precise branching ratios to unbound states in 12 C from 12 N and 12 B β-decays. In the first the three α-particles emitted after βdecay are measured in coincidence in separate detectors, while in the second method 12 N and 12 B are implanted in a detector and the summed energy of the three α-particles is measured directly. For the narrow states at 7.654 MeV (0 +) and 12.71 MeV (1 +) the resulting branching ratios are both smaller than previous measurements by a factor of 2. The experimental results are compared to no-core shell model calculations with realistic interactions from chiral perturbation theory, and inclusion of three-nucleon forces is found to give improved agreement.
The β decays of 12 N and 12 B have been studied at KVI and JYFL to resolve the composition of the broad and interfering 0 + and 2 + strengths in the triple-α continuum. For the first time a complete treatment of 3α decay is presented including all major breakup channels. A multilevel, many-channel R-matrix formalism has been developed for the complete description of the breakup in combination with the recently published separate analysis of angular correlations. We find that, in addition to the Hoyle state at 7.65 MeV, more than one 0 + and 2 + state is needed to reproduce the spectra. Broad 0 + 3 and 2 + 2 states are found between 10.5 and 12 MeV in this work. The presence of β strength up to the 12 N Q-value window suggests the presence of additional 0 + and 2 + components in the 12 C structure at energies above 12.7 MeV.
The TRIµP facility, under construction at KVI, requires the production and separation of short-lived and rare isotopes. Direct reactions, fragmentation and fusionevaporation reactions in normal and inverse kinematics are foreseen to produce nuclides of interest with a variety of heavy-ion beams from the superconducting cyclotron AGOR. For this purpose, we have designed, constructed and commissioned a versatile magnetic separator that allows efficient injection into an ion catcher, i.e., gas-filled stopper/cooler or thermal ionizer, from which a low energy radioactive beam will be extracted.The separator performance was tested with the production and clean separation of 21 Na ions, where a beam purity of 99.5% could be achieved. For fusion-evaporation products, some of the features of its operation as a gas-filled recoil separator were tested.
Efficient production of short-lived radioactive isotopes in inverse reaction kinematics is an important technique for various applications. It is particularly interesting when the isotope of interest is only a few nucleons away from a stable isotope. In this article production via charge exchange and stripping reactions in combination with a magnetic separator is explored. The relation between the separator transmission efficiency, the production yield, and the choice of beam energy is discussed. The results of some exploratory experiments will be presented.
The 1 2 + → 1 2 + superallowed mixed mirror decay of 19 Ne to 19 F is excellently suited for high precision studies of the weak interaction. However, there is some disagreement on the value of the half-life. In a new measurement we have determined this quantity to be T 1/2 = 17.2832 ± 0.0051 (stat) ± 0.0066 (sys) s, which differs from the previous world average by 3 standard deviations. The impact of this measurement on limits for physics beyond the standard model such as the presence of tensor currents is discussed.PACS numbers: 24.80.+y,12.15.Hh, We can precisely characterize the structure of the weak interaction and probe for physics Beyond the Standard Model (BSM) in nuclear beta decay by searching for a deviation from unitarity of the Cabibbo-KobayashiMaskawa (CKM) matrix, and by constraining the presence of new, exotic interactions which would manifest as scalar or tensor couplings. Currently, the thirteen, purely vector, superallowed 0 + → 0 + Fermi decays provide the most precise determination of the CKM matrix element governing nuclear beta decay, |V ud | = 0.97425(22), and the most stringent constraint on scalar couplings from the constancy of the Ft values [1]. The superallowed, mixed Fermi/Gamow-Teller transitions between T = 1 2 mirror nuclei can provide a needed cross check of the nucleus dependent theoretical corrections which contribute significantly to the overall uncertainty, and have been used to extract |V ud | = 0.9719 (17) [2], where the 19 Ne system is the most precise component. The 19 Ne system is capable of very sensitive tests for right-handed currents due to the very small beta asymmetry [3], and we show that it can be used to obtain complementary limits on tensor couplings.Mixed decays require a measurement of the half-life and an angular correlation to perform SM tests, in order to fix the Fermi/Gamow-Teller mixing ratio ρ. Until recently, the uncertainty in the 19 Ne half-life determination was several times higher than all other contributions to the uncertainty in the Ft value, and was on par with the contribution of the beta asymmetry parameter to the uncertainty of V ud . There is some disagreement between the published values of the lifetime, represented by a χ 2 /NDF of 41.2/7 for the global data set. This discrepancy has been addressed in our experiment through a novel approach which addressed with improved relia-
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