Fermion mass hierarchies from vector-like families and possible explanations for the electron and muon anomalous magnetic moments

TL;DR

This thesis explores minimal extensions of the Standard Model using vector-like families and $U(1)^$ symmetry to explain fermion mass hierarchies and anomalies in electron and muon magnetic moments, analyzing scalar and neutrino contributions.

Contribution

It introduces new BSM models with vector-like families and $U(1)^$ symmetry that simultaneously address fermion mass hierarchies and lepton magnetic moment anomalies.

Findings

Scalar contributions can explain both anomalies simultaneously.

Neutrino contributions are too small to account for the anomalies.

No parameter values between certain mass ranges satisfy the anomalies.

Abstract

This thesis covers a few successes of the SM and its limitations. The limitations implement that the SM must be expanded to explain the observables which can not be addressed by the SM such as mass of neutrinos, a few of anomalies, DM, DE, etc. In order to extend the SM, we take the model-dependent approach and a minimal extension to the SM. For the minimal extension, we make use of vector-like family, SM-like scalar (plus a singlet flavon), and $U(1)^\prime$ symmetry. A first BSM model in my first work is to explain both the electron and muon anomalous magnetic moments at the same time, while keeping the constraints $\mu \rightarrow e \gamma$ decay and neutrino trident production. Especially, two mass sources, chirality flip and vector-like mass, appear in our analytic prediction for the anomalies and the chirality flip mass between $0$ and $200 \operatorname{GeV}$ is searched and then we show no any value between them can satisfy the anomalies at the same time. A second BSM model in my second work shares the same motivation, to explain both anomalies, however it goes one step further by considering the strong hierarchical structure of the SM into the second BSM model. In this BSM model, the SM appears as an effective theory spontaneously broken from the $U(1)^\prime$ symmetry. Both anomalies are studied in the neutrino sector first and it reveals that the neutrino contributions are too small to explain their experimental bounds, so leading to a conclusion that the neutrinos can not explain both anomalies simultaneously. Next we study the scalar contribution and show that the scalar contributions can explain both anomalies simultaneously. My third work investigate the diverse FCNCs within the same second BSM model to constrain mass range of vector-like fermions.