The Physics Colloquium: Geoff Greene (University of Tennessee) "The Neutron Lifetime, Why do we keep measuring it? & Why do we keep getting it “wrong”?"

The beta decay of the free neutron is the simplest example of the Weak Interaction between quarks and leptons. Because of its simplicity the value of the neutron lifetime can be directly related to a variety of important phenomena including Big Bang nucleosynthesis, supernova core collapse, and energy production in the sun. In addition, the precise value of the neutron lifetime can be compared with other decay information to provide a test of the Standard Model of Particle Physics. In light of its importance, it is distressing to note that there is a significant discrepancy between measurements of the neutron lifetime done by different methods. In this talk I will review the phenomenology of neutron beta decay and discuss, among other things, how the neutron lifetime enters into the details of the Big Bang. I will review measurement methodologies and conclude with a discussion of the reliability of measurement error estimation and why large discrepancies seem to occur too frequently.