Author ORCID Identifier

https://orcid.org/0000-0003-0913-0496

Date Available

12-15-2024

Year of Publication

2024

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Arts and Sciences

Department/School/Program

Physics and Astronomy

Advisor

Christopher B. Crawford

Abstract

Over the last couple decades, use of free neutron beta decay (n → p + e- + νe) to extract the up-down quark transition element Vud has become competitive with more conventional Fermi decays. Extraction of Vud requires measurements of the vector to axial-vector coupling constant ratio λ and the free neutron lifetime τn. With a precise determination of Vud, the 2.8σ departure from CKM unitarity can be addressed.

Nab, located at the Spallation Neutron Source at ORNL, will measure the electron-neutrino momentum correlation coefficient a (which couples quadratically to λ) to relative precision of 0.1% (Δλ/λ ~ 0.04%) in addition to the Fierz interference term bF with an absolute precision of 3x10-3. The latter is zero under V-A theory and thus serves as a direct probe into Beyond the Standard Model Physics. BL3, at NIST, is an improvement on the ILL-NIST beam lifetime method with a precision goal of Δτn < 0.3 s. Minimization of systematic uncertainties associated with this method will also address the apparent 4σ discrepancy between beam and bottle lifetime experiments.

This dissertation presents methods of optimizing these measurements via absolute neutron flux monitoring for BL3, rapid real-time waveform processing with efficient triggering and beta decay detection logic, and in-situ amplifier temperature control for Nab.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.461

Funding Information

This research was funded in part by the following grants and awards:

  • Department of Energy, Office of Science, DE-SC0014622: from May 2020 to June 2022 and from June 2023 to November 2024.
  • Department of Energy, Office of Science, Graduate Student Research Fellowship, DE-SC0014664: from June 2022 to June 2023.

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