Minimal seesaw model with [formula omitted] flavor symmetry

Rui-Zhi Yang,He Zhang

doi:10.1016/j.physletb.2011.05.014

Abstract

We discuss a neutrino mass model based on the S4 flavor symmetry within the minimal seesaw framework, in which only two right-handed neutrinos are introduced and transform as 2 under S4. Although the model contains less free parameters compared to the typical seesaw models, it provides a successful description of the observed neutrino parameters, and in particular, a nearly tri-bimaximal mixing pattern can be naturally accommodated. In addition, the heavy right-handed neutrino masses are found to be non-degenerate, while only the normal hierarchical mass spectrum is compatible with experiments for light neutrinos.

Highlights

In view of the compelling experimental evidence on neutrino oscillations, the origin of neutrino masses and lepton flavor mixing emerges as one of the most fundamental issues in particle physics
Since neutrinos are massless particles in the standard model (SM) of particle physics, a broad class of models extended the SM have been proposed in order to accommodate massive neutrinos
In the canonical type-I seesaw model, three heavy righthanded neutrinos are introduced besides the SM particle contents, while a Majorana mass term MR is assumed, which is not subjected to the scale of electroweak symmetry breaking scale, i.e., ΛEW ∼ 100 GeV

Summary

INTRODUCTION

In view of the compelling experimental evidence on neutrino oscillations, the origin of neutrino masses and lepton flavor mixing emerges as one of the most fundamental issues in particle physics. In the most economical type-I seesaw model, i.e., the minimal seesaw model (MSM) [9,10,11,12], one could introduce only two right-handed neutrinos, whereas the observed neutrino mass hierarchy and lepton flavor mixing can be well interpreted. Such a minimal extension of the SM greatly reduces the number of free parameters, and is very predictive. The total symmetry of our model is chosen to be

Charged lepton masses

Neutrino mass matrix

Lepton flavor mixing

Higgs potential

NUMERICAL ILLUSTRATIONS

CONCLUSION