A Model of Lepton Masses from a Warped Extra Dimension

TL;DR

This paper proposes a simple warped extra dimension model with A4 symmetry that naturally explains lepton masses and mixings, avoids flavor violations, and is compatible with current experimental bounds.

Contribution

It introduces a minimal A4-symmetric model in warped extra dimensions that achieves realistic lepton mixing patterns without tree-level flavor violations.

Findings

Tri-bimaximal mixing pattern naturally emerges.

Tree-level flavor violations are absent.

KK mass scale can be as low as 3 TeV.

Abstract

In order to explain the non-hierarchical neutrino mixing angles and the absence of lepton flavor violating processes in the context of warped extra dimensions one needs to introduce bulk flavor symmetries. We present a simple model of lepton masses and mixings in RS models based on the A4 non-abelian discrete symmetry. The virtues of this choice are: (i) the natural appearance of the tri-bimaximal mixing pattern; (ii) the complete absence of tree-level flavor violations in the neutral sector; (iii) the absence of flavor gauge bosons; (iv) the hierarchies in the charged lepton masses are explained via wave-function overlaps. We present the minimal field content and symmetry breaking pattern necessary to obtain a successful model of this type. The bounds from electroweak precision measurements allow the KK mass scale to be as low as 3 TeV. Tree-level lepton flavor violation is absent in this model, while the loop induced mu -> e gamma branching fraction is safely below the experimental bound.