The Decay of the Neutron or Beta Decay, the Big Bang, and the Left-Handed Universe

01:00 PM - 02:30 PM
Geoffrey L. Greene Physics Division, ORNL
Research Accelerator Division Seminar
SNS Central Laboratory and Office Building (8600), Room C-156
Email: Sarah Cousineau

Neutrons within nuclei may be stable, but the free neutron is unstable against beta decay and has a mean lifetime of ~15min. Free neutron beta decay is, perhaps, the simplest weak nuclear process as it is uncomplicated by many body effects that are present in the decay of heavy nuclei. As a result, it can be understood in terms of rather simple fundamental weak interaction theory. Because free neutron decay is the "prototype" for all nuclear beta decays, the neutron lifetime is a fundamental parameter whose value is important not only in nuclear physics, but also in astrophysics, cosmology, and particle physics. I will give an introduction to the theory of nuclear decay and briefly discuss the importance of the neutron lifetime as a parameter in the Big Bang. A review of the experimental strategies for the measurement of the neutron lifetime will be given as well as a discussion of the puzzling discrepancy among the measurements with the lowest quoted uncertainty. Finally, I present a very new result recently obtained at the NIST Cold Neutron Research Facility in Gaithersburg Md.


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