A common origin of the Higgs boson and the flavor hierarchies

TL;DR

This paper proposes a model where a new composite sector explains both the origin of the Higgs boson as a pseudo-Nambu-Goldstone boson and the flavor hierarchies among fermion families, linking electroweak symmetry breaking with flavor structure.

Contribution

It introduces a novel extended gauge symmetry and flavor symmetry framework that naturally generates the Higgs as a composite state and explains flavor hierarchies and mixing patterns.

Findings

Higgs emerges as a pseudo-Nambu-Goldstone boson from strong dynamics.

Flavor hierarchies are explained by higher-dimensional operators and symmetry structure.

Suppressed mixing angles between third and light families are naturally obtained.

Abstract

We present a model that extends the electroweak gauge symmetry of the Standard Model in a non-universal way to $SU(2)_{L}^{\prime}\times U(1)_X \times SU(2)_{L}^{q_3}\times SU(2)_R^{\ell_3}$. This symmetry is spontaneously broken to $SU(2)_L\times U(1)_Y$ near the TeV scale by a condensate of a new composite sector. Charging appropriately the fermionic degrees of freedom of the composite sector, anomaly cancellation enforces the Standard Model fermions to be charged in such a way that the extended gauge interactions respect a $U(2)_q\times U(2)_e\times U(3)_u\times U(3)_d\times U(3)_\ell$ accidental flavor symmetry. In addition, from the same symmetry breaking, a composite Higgs boson emerges as a pseudo-Nambu-Goldstone boson of the strong dynamics of the new sector. Due to the extended gauge and the specific flavor symmetry, leading Yukawa couplings between Higgs and fermions can only be written for the third generation and higher dimension operators generate suppressed light-family Yukawa couplings. Furthermore, CKM mixing angles between third and light families are naturally suppressed while the PMNS ones, anarchic. The model thus provides a unified origin for the Higgs boson and the flavor hierarchies between third and light families.