Leptonic flavor structure in the brane shifted extra dimensional seesaw mechanism

Mathias Becker,Heinrich Päs

doi:10.1140/epjc/s10052-018-5756-6

Mathias Becker, Heinrich Päs

Open Access

https://doi.org/10.1140/epjc/s10052-018-5756-6

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Abstract

We discuss the leptonic flavor structure generated by a brane shifted extra dimensional seesaw model with a single right handed neutrino in the bulk. In contrast to previous works, no unitarity approximation for the 3 times 3 submatrix has been employed. This allows to study phenomenological signatures such as lepton flavor violating decays. A strong prediction of the model, assuming CP conservation, are the ratios of flavor violating charged lepton decay and Z decay branching ratios which are correlated with the neutrino mixing angles and the neutrino mass hierarchy. Furthermore, it is possible to obtain branching ratios for mu rightarrow e gamma close to the experimental bounds even with Yukawa couplings of order one.

Highlights

In the last decade compactified large extra dimensions (LED) attracted a lot of attention [1,2], by providing an attractive possibility to solve the hierarchy problem. This can be achieved by allowing Standard Model (SM) singlets, e.g. gravitons, to propagate in spatial extra dimensions leading to a suppression of the Planck scale by a volume factor of the extra dimensions
We have studied an extra dimensional seesaw mechanism with a single right handed bulk neutrino
We have worked out the flavor structure without adopting a non-unitarity approximation of the 3 × 3 submatrix

Summary

Introduction

In the last decade compactified large extra dimensions (LED) attracted a lot of attention [1,2], by providing an attractive possibility to solve the hierarchy problem This can be achieved by allowing Standard Model (SM) singlets, e.g. gravitons, to propagate in spatial extra dimensions leading to a suppression of the Planck scale by a volume factor of the extra dimensions. For previous discussions of extra dimensional models with branes shifted away from the orbifold fixed points compare [4,5,7,8], while in [15] the first string realization of low scale gravity and braneworlds was given. Which is necessary to solve the hierarchy problem, a larger number of extra dimensions is needed to obtain a seesaw kind of behavior. Note that in principle even in the red regions of the plot it is possible to obtain a seesaw kind of behavior by choosing a small value for the 5D Yukawa coupling

Neutrino masses and mixing

Unitarity violation and lepton flavor violation

Summary and conclusions