#### Year of Publication

2013

#### Degree Name

Doctor of Philosophy (PhD)

#### Document Type

Doctoral Dissertation

#### College

Arts and Sciences

#### Department

Physics and Astronomy

#### First Advisor

Dr. Susan Gardner

#### Abstract

CP violation is an important condition to explain the preponderance of baryons in our universe, yet the available CP violation in the Standard Model (SM) via the so-called Cabibbo-Kobayashi-Maskawa mechanism seems to not provide enough CP violation. Thus searching for new sources of CP violation is one of the central tasks of modern physics. In this thesis, we focus on a new possible source of CP violation which generates triple-product correlations in momenta which can appear in neutron and nuclear radiative *β* decay. We show that at low energies such a CP violating correlation may arise from the exotic coupling of nucleon, photon and neutrino that was proposed by Harvey, Hill, and Hill (HHH). One specialty of such an exotic HHH coupling is that it does not generate the well-known CP-violating terms such as ``D-term'', ``R-term'', and neutron electric dipole moment, in which particle's spins play critical role. We show that such a new HHH-induced CP violating effect is proportional to the imaginary part of *c*_{5}*gv*, where *gv* is the vector coupling constant in neutron and nuclear *β* decay, and *c*_{5} is the phenomenological coupling constant that appears in chiral perturbation theory at *O*(*M*^{-2}) with *M* referring to the nucleon or nuclear mass. We consider a possible non-Abelian hidden sector model, which is beyond the SM and may yield a nontrivial Im(*c*_{5}). The available bounds on both Im(*c*_{5}) and Im(*gv*) are considered, and a better limit on Im(*c*_{5}) can come from a direct measurement in radiative beta decay. We calculate the competitive effect that arises from the general parameterization of the weak interaction that was proposed by Lee and Yang in 1956. We also show that in the proposed measurements, the CP-violating effect can be mimicked by the SM via final-state interactions (FSI). For a better determination of the bound of Im(*c*_{5}), we consider the FSI-induced mimicking effect in full detail in *O*(*α*) as well as in leading recoil order. To face ongoing precision measurements of neutron radiative *β* decay of up to 1% relative error, we sharpen our calculations of the CP conserving pieces of neutron radiative *β* decay by considering the largest contributions in *O*(*α*^{2}): the final-state Coulomb corrections as well as the contributions from two-photon radiation.

#### Recommended Citation

He, Daheng, "Investigation of Spin-Independent CP Violation in Neutron and Nuclear Radiative β Decays" (2013). *Theses and Dissertations--Physics and Astronomy*. 13.

https://uknowledge.uky.edu/physastron_etds/13