Electric Dipole Moments of Charged Leptons with Sterile Fermions

TL;DR

This paper investigates how sterile neutrinos can influence the electric dipole moments of charged leptons, revealing potential signals of physics beyond the Standard Model and emphasizing the importance of sterile neutrino properties.

Contribution

It provides analytical expressions for charged lepton EDMs with sterile neutrinos and shows that at least two sterile states are needed for non-zero contributions, highlighting their experimental relevance.

Findings

Sterile neutrinos can significantly contribute to charged lepton EDMs.

Non-degenerate sterile states above the electroweak scale are within experimental sensitivity.

Majorana neutrinos are crucial for sizable EDM contributions.

Abstract

We address the impact of sterile fermions on charged lepton electric dipole moments. Any experimental signal of these observables calls for scenarios of physics beyond the Standard Model providing new sources of CP violation. In this work, we consider a minimal extension of the Standard Model via the addition of sterile fermions which mix with active neutrinos and we derive the corresponding analytical expressions for the electric dipole moments of charged leptons at two-loop order. Our study reveals that, in order to have a non-vanishing contribution in this framework, the minimal extension necessitates the addition of at least 2 sterile fermion states to the Standard Model field content. Our conclusion is that sterile neutrinos can give significant contributions to the charged lepton electric dipole moments, some of them lying within present and future experimental sensitivity if the masses of the non-degenerate sterile states are both above the electroweak scale. The Majorana nature of neutrinos is also important in order to allow for significative contributions to the charged lepton electric dipole moments. In our analysis we impose all available experimental and observational constraints on sterile neutrinos and we further discuss the prospect of probing this scenario at low and high energy experiments.