The third family quark mass hierarchy and FCNC in the universal seesaw model

TL;DR

This paper explores the quark mass hierarchy and flavor-changing neutral currents within a universal seesaw model featuring extended gauge symmetry, introducing vector-like quarks to explain the third family quark masses.

Contribution

It explicitly formulates the Lagrangian for the quark, Higgs, and gauge sectors under the extended gauge symmetry, and analyzes FCNC processes involving top and bottom quarks.

Findings

Derived the invariant Lagrangian at each symmetry-breaking stage.

Analyzed FCNC interactions of Higgs and Z bosons with heavy and light quarks.

Provided insights into the mass hierarchy of the third quark family.

Abstract

We present the study of the quark sector of the universal seesaw model with $\mathrm{SU(2)_L \times SU(2)_R \times U(1)_{Y'}}$ gauge symmetry in the massless case of the two lightest quark families. This model aims to explain the mass hierarchy of the third family quark by introducing a vector-like quark (VLQ) partner for each quark. In this model, we introduce $\mathrm{SU(2)_L}$ and $\mathrm{SU(2)_R}$ Higgs doublets. We derive explicitly the Lagrangian for the quark sector, Higgs sector, and kinetic terms of the gauge fields, starting from the Lagrangian, which is invariant under $\mathrm{SU(2)_L \times SU(2)_R \times U(1)_{Y'}}$ gauge symmetry. At each stage of the symmetry breaking, we present the Lagrangian with the remaining gauge symmetry. Additionally, we investigate the flavor-changing neutral currents (FCNC) of Higgs ($h$) and $Z$-boson in the interaction with the top, heavy top, bottom, and heavy bottom quark.