Effect of steriles states on lepton magnetic moments and neutrinoless double beta decay

A Abada,A M Teixeira,V De Romeri

doi:10.1007/jhep09(2014)074

Abstract

We address the impact of sterile fermion states on the anomalous magnetic moment of charged leptons, as well as their contribution to neutrinoless double beta decays. We illustrate our results in a minimal, effective extension of the Standard Model by one sterile fermion state, and in a well-motivated framework of neutrino mass generation, embedding the Inverse Seesaw into the Standard Model. The simple “3+1” effective case succeeds in alleviating the tension related to the muon anomalous magnetic moment, albeit only at the 3σ level, and for light sterile states (corresponding to a cosmologically disfavoured regime). Interestingly, our analysis shows that a future 0ν2β observation does not necessarily imply an inverted hierarchy for the active neutrinos in this simple extension. Although the Inverse Seesaw realisation here addressed could indeed ease the tension in (g − 2) μ , bounds from lepton universality in kaon decays mostly preclude this from happening. However, these scenarios can also have a strong impact on the interpretation of a future 0ν2β signal regarding the hierarchy of the active neutrino mass spectrum.

Highlights

We address the impact of sterile fermion states on the anomalous magnetic moment of charged leptons, as well as their contribution to neutrinoless double beta decays
Our analysis reveals that scenarios with sterile fermions can contribute to alleviate the (g − 2)μ tension and, more importantly, can have a strong impact on the interpretation of a future 0ν2β signal regarding the hierarchy of the active neutrino mass spectrum
In this work we investigated the role of sterile neutrinos on the magnetic moment of leptons, as well as their contribution to the neutrinoless double beta decay effective mass

Summary

Introduction

The most minimal of these extensions consists in an effective, ad-hoc model, where one sterile state is added to the neutral fermion content of the SM In this so called “3+1” effective framework, the additional state encodes the effect of a given (arbitrary) number of sterile fermions, and their mixings with the active (light) neutrinos. In this approach no assumption is made concerning the underlying mechanism of neutrino mass generation. As an illustrative example of a low-scale model of neutrino mass generation we considered a realisation of the ISS mechanism with 3 right-handed neutrinos and 3 additional sterile states ( on labeled for simplicity “ISS model”).

Objectives

Discussion

Conclusion