Z_4 flavor model in Randall-Sundrum model 1

TL;DR

This paper combines Randall-Sundrum models with a Z_4 flavor symmetry in a five-dimensional framework to naturally generate fermion mass hierarchies and neutrino masses without right-handed neutrinos, using minimal Higgs content.

Contribution

It introduces a novel 5D extension of the Standard Model incorporating Z_4 flavor symmetry and Scherk-Schwarz mechanism for symmetry breaking, with radiative neutrino mass generation.

Findings

Achieves fermion mass hierarchy with order 1 localization parameters.

Provides a minimal model requiring only two brane Higgs fields.

Identifies allowed parameter regions consistent with neutrino data.

Abstract

Randall Sundrum models provide a possible explanation of (gauge-gravity) hierarchy, whereas discrete symmetry flavor groups yield a possible description of the texture of Standard Model fermion masses. We use both these ingredients to propose a five-dimensional extension of the Standard Model where the mass hierarchy of the four-dimensional effective field theory is obtained only using localizations parameters of order 1. We consider a bulk custodial gauge symmetry group together with an Abelian $Z_4$ group: the model turns out to yield a rather minimal extension of the SM as it only requires two brane Higgs fields to provide the desired Yukawa interactions and the required spontaneous symmetry breaking pattern. In fact, the presence of an extra-dimension allows the use of the Scherk-Schwarz mechanism to contribute to the breaking of the bulk custodial group down to the SM gauge symmetry. Moreover, no right-handed neutrinos are present and neutrino masses are generated radiatively with the help of a bulk charged scalar field that provides the Lepton-number violation. Using experimental inputs from the Global Neutrino Analysis and recent Daya Bay results, a numerical analysis is performed and allowed parameter regions are displayed.