Mixing of Charge -1/3 Quarks and Charged Leptons With Exotic Fermions in E$_{\rm 6}$

TL;DR

This paper proposes a novel explanation for the mass differences among down-type quarks by introducing mixing with exotic fermions within the E6 unification framework, avoiding the need for different Higgs VEVs or Yukawa couplings.

Contribution

It introduces a new mechanism based on exotic fermion mixing in E6 to explain quark mass hierarchies, differing from previous models.

Findings

Mass differences explained by mixing with exotic fermions

Provides a unified group-theoretic basis for quark and lepton masses

Avoids reliance on multiple Higgs VEVs or Yukawa coupling variations

Abstract

A way is suggested to understand why the average masses of $(d,s,b)$ quarks are smaller than those of $(u,c,t)$ quarks. In contrast to previously proposed mechanisms relying on different Higgs boson vacuum expectation values or different Yukawa couplings, the mass difference is explained as a consequence of mixing of $(d,s,b)$ with exotic quarks implied by the electroweak-strong unification group E$_{\rm 6}$.