Measurement of the Neutron Beta Decay Asymmetry using Ultracold Neutrons

Citation

Mendenhall, Michael Praetorius (2014) Measurement of the Neutron Beta Decay Asymmetry using Ultracold Neutrons. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9TS2-SG08. https://resolver.caltech.edu/CaltechTHESIS:06042014-132823956

Abstract

The free neutron beta decay correlation A₀ between neutron polarization and electron emission direction provides the strongest constraint on the ratio λ = g_A/g_V of the Axial-vector to Vector coupling constants in Weak decay. In conjunction with the CKM Matrix element V_ud and the neutron lifetime τ_n, λ provides a test of Standard Model assumptions for the Weak interaction. Leading high-precision measurements of A₀ and τ_n in the 1995-2005 time period showed discrepancies with prior measurements and Standard Model predictions for the relationship between λ, τ_n, and V_ud. The UCNA experiment was developed to measure A₀ from decay of polarized ultracold neutrons (UCN), providing a complementary determination of λ with different systematic uncertainties from prior cold neutron beam experiments. This dissertation describes analysis of the dataset collected by UCNA in 2010, with emphasis on detector response calibrations and systematics. The UCNA measurement is placed in the context of the most recent τ_n results and cold neutron A₀ experiments.

Thesis Files