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

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.