Measurement of the neutrino asymmetry in the beta decay of laser-cooled, polarized 37k

The TRINAT collaboration began investigating fundamental symmetries searching for scalar contributions to the predominantly V - A structure of the weak interaction by measuring the /3 - v correlation parameter using the pure Fermi decay of magnetooptically trapped 38mK . This thesis describes the first physics measurement using polarized, laser-cooled 3 7 ~ , and represents the next generation of TRINAT experiments aimed at searching for right-handed currents predicted to restore parity at higher energy scales in some extensions to the Standard Model. Using a detector geometry similar to that of the scalar search, we have learned to implement optical pumping techniques to achieve very high (2 96%) nuclear polarizations of our radioactive atom sample. Furthermore, we have pioneered techniques to measure this observable - independent of the /3 decay observables - in situ on all the nuclei that are decaying. By observing the emitted /3+ and recoiling 37Ar in the back-to-back geometry, we have extracted a measurement of the neutrino asymmetry parameter: B, = -0.755 f 0.020 f 0.013, in agreement with the Standard Model (stat) (syst) prediction of -O.7692(15). This 3% measurement of the B, represents the first /3 decay physics measurement using a polarized, laser-cooled source. This is not yet competitive with other limits on right-handed current parameters; however, we have identified our dominant systematics and have learned how to minimize them so that the next time the experiment is performed, we expect to be able to reduce our uncertainty to the 0.5% level. Additionally, we have outlined how we may make use of a correlation unique to our setup to further enhance our sensitivity. We expect that future experiments will be able to have a significant impact in either finding new physics or helping to constrain the variety of models considered as viable extensions to the Standard Model.