Author ORCID Identifier

https://orcid.org/0000-0002-3855-5373

Date Available

12-21-2022

Year of Publication

2022

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Arts and Sciences

Department/School/Program

Physics and Astronomy

Advisor

Dr. Bradley Plaster

Abstract

It is thought that equal quantities of matter and antimatter were generated at the moment of the Big Bang. However, observations of the Universe show that there is a significant excess of matter over antimatter. The matter-antimatter asymmetry in the Universe (baryon to photon ratio) is observed to be of the order of 10-10 [1]. Baryogenesis is a possible explanation for the matter-antimatter asymmetry of the universe. In 1967, Sakharov proposed three criteria necessary for Baryogenesis. The three conditions are: 1) baryon number violation, 2) C and CP violation and 3) departure from thermal equilibrium. However, the Standard Model's prediction of C and CP violation is not enough to explain the observed matter-antimatter asymmetry. Physicists have been seeking for Standard Model (SM) modifications in attempt to discover an explanation. A nonzero neutron electric dipole moment (nEDM) violates the T and P symmetries, which leads to CP violation due to CPT conservation.

In 1951, Oak Ridge hosted the first experiment to search for a neutron EDM (dn) that led to dn = -(0.1 ± 2.4) * 10-20 e.cm. Later, in 1977, the improved method's sensitivity reached  dn = 3 *10-24 e.cm (90% CL). In 2006, Baker et al. at the Institute Laue-Langevin cut the upper limit by almost two orders of magnitude. The ILL apparatus deployed by the RAL/Sussex/ILL collaboration at the Paul Scherrer Institut (PSI) in 2020 established the current limitations of the nEDM |dn| < 1.8 * 10-26 e.cm (90% CL). A cryogenic device based on a unique idea devised by Golub and Lamoreaux [2] is being constructed at Oak Ridge National Laboratory's Spallation Neutron Source (SNS) to improve the sensitivity of nEDM studies. The experiment uses superfluid 4He to produce a high density of Ultra-Cold Neutrons (UCN). The Larmor precession of the UCNs is then monitored by the scintillation signals due to the spin-dependent interaction rate of UCNs and 3He atoms.

One of the central problems to any nEDM experiment is the stability of the magnetic field. Hence, in general, the experiment depends on a precise system of magnetometers that monitor the average magnetic field over the region where the neutrons precess. Accordingly, the nEDM@SNS experiment takes advantage of polarized 3He atoms as a co-magnetometer via detection of the precessing 3He magnetization in SQUID pickup loops. This document will outline the simulation of scintillation and SQUID signals in the presence of time-varying magnetic fields, and developing data analysis techniques to detect these time-variations and correct their effect from the nEDM measurement.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2022.445

Funding Information

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE-SC0014622.

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