Doctor of Philosophy (PhD)
Physics and Astronomy
Nuclear physics today is a diverse field, involving research that extends from the minus- cule scales of neutrons and protons to the colossal dimensions of astrophysical objects in the universe. And since the ab initio methods in nuclear physics use realistic internucleon interactions, nuclear modeling has gained predictive capabilities that enable us to probe ever more deeply into the fundamental nature of matter. One of these models – the symmetry- adapted no-core shell model (SA-NCSM) – is capable of reaching the medium-mass region of the chart of the nuclides, by exploiting the emergent symmetries of nuclei, and is therefore well-suited for studying collective correlations and beta decay modes.
We apply the SA-NCSM to calculate beta-decay observables essential to probe physics beyond the Standard Model. One of the most challenging problems in physics today is whether the neutrino is its own antiparticle. This work sets a limit – from first principles – on the nuclear structure piece needed by experimentalists to extract the type of the neutrino (Dirac or Majorana) from state-of-the-art measurements of the half-life of the hypothetical neutrinoless double-beta decay. Furthermore, our calculations of higher-order recoil terms in the beta decay of 8Li help to significantly reduce the uncertainties in high-precision experiments that study the vector minus axial vector (V−A) structure of the weak interaction.
In addition, to gain a better understanding of the 8Li beta-decay final states, we examine their cluster substructures such as the single-nucleon and alpha cluster wavefunctions. The method is then applied to a series of Li isotopes. The single-nucleon cluster wavefunctions are used in calculations of reaction observables, which in turn paves the way for calculations of optical potentials for nucleon projectiles from first principles.
Sargsyan, Grigor, "Electromagnetic Transitions and Beta Decays in Nuclei from the Ab initio Symmetry-adapted No-core Shell Model" (2021). LSU Doctoral Dissertations. 5641.