Abstract
A program to investigate the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix by studying super-allowed mixed mirror β decays has been initiated at the TwinSol facility at Notre Dame. These mixed Fermi/Gamow-Teller (F-GT) decays, occurring between T=1/2 isospin doublets in mirror nuclei, provide a complimentary check on the data from super-allowed pure Fermi decays from 0+to 0+ states. The first part of the program, involving the measurement of the lifetimes of the relevant nuclei to the required accuracy of one part in 103 or better, has nearly been completed. However, the additional complication introduced by F-GT mixing requires the use of an ion trap to measure the mixing ratio ρ with similar accuracy. The lifetime measurements, as well as progress in installing an ion trap at TwinSol, will be discussed. In addition, since the ion trap will require a dedicated beam line for its operation, an opportunity presented itself to greatly improve the performance of TwinSol for reaction studies with exotic nuclei. This took the form of an added dipole switching magnet coupled to a third solenoid to form the new TriSol facility currently under construction. The expected properties of TriSol, and its application to reaction studies of interest for nuclear astrophysics, will also be discussed.
Highlights
One important test of the Standard Model (SM) of highenergy physics is via the unitarity of the CKM matrix: CKM = VVVuctddd
Non-unitarity of this matrix would imply the possibility of physics beyond the SM
The largest element in the summation, |Vud|2, is accessible through nuclear β decay, and its most precise measurement is via super-allowed pure Fermi decays from 0+to 0+ states (Figure 1)
Summary
One important test of the Standard Model (SM) of highenergy physics is via the unitarity of the CKM matrix: CKM = VVVuctddd. Non-unitarity of this matrix would imply the possibility of physics beyond the SM. The largest element in the summation, |Vud|2, is accessible through nuclear β decay, and its most precise measurement is via super-allowed pure Fermi decays from 0+to 0+ states (Figure 1). The required parameters for such a measurement include the half-life, Q-value, branching ratios, and F-GT mixing ratio ρ for the transition. Along with some nuclear correction factors, must be determined with a precision of better than one part in 103. A program to determine the relevant half-lives using radioactive beams from TwinSol will be described below, together with progress on construction of an ion trap to measure ρ
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