Grant: Subatomic Physics Envelope - Research Tools and Instruments

Using TRIUMF's atom trap for nuclear beta decay (TRINAT), we have measured the beta asymmetry with respect to the nuclear spin in 37K, Abeta, to be -0.5707+-0.0019. This is the most accurate beta asymmetry measurement in any nucleus or the neutron, and is in agreement with the prediction of the Standard Model of particle physics.*The standard model prediction for Abeta is presently limited by experimental determination of the relative contributions of the two allowed operators, Fermi and Gamow-Teller. We seek improvements of two observables that depend on the momentum of the various decay products, and are independent of the Fermi/Gamow-Teller ratio. The energy dependence Abeta[Ebeta] is being implemented from our project grant and last year's RTI to improve the spin polarization and upgrade this experiment to accept lower-energy betas.* We thus seek improvements in this RTI to in-vacuum ion detection instrumentation to enable a new and complementary experiment on the spin asymmetry of the recoiling nuclei in singles, along with beta-recoil coincidences that are even less dependent on theoretical corrections. The recoil asymmetry in singles would have very high statistics, and holds the promise of an order of magnitude improvement in sensitivity over existing beta decay measurements to certain types of interactions. * Our new Canadian M.Sc. student would implement this equipment for an instrumental M.Sc., which should lead to a Ph.D. project on these experiments. We continue to provide opportunities to one undergrad at a time to help us develop the instrumentation and learn the background physics.*We also wish to begin an experiment in time-reversal violation in radiative beta decay. This correlation of 3 momenta does not involve spin, relaxing constraints on it from experiments involving spin (like electric dipole moment searches). We are applying for funds for simple gamma-ray detectors to add to the present TRINAT apparatus.*