Radiative generation of neutrino mixing: degenerate masses and threshold corrections

TL;DR

This paper demonstrates that electroweak scale threshold corrections, especially flavor-violating ones, can generate realistic neutrino mixing and mass differences from degenerate masses, within a supersymmetric framework.

Contribution

It shows that one-loop threshold corrections can produce observed neutrino properties from degenerate masses, emphasizing the role of flavor violation in these corrections.

Findings

Flavor-violating threshold corrections are necessary to generate correct neutrino mixing.

Non-universal, flavor-diagonal corrections alone are insufficient.

Application to a supersymmetric model illustrates the mechanism's viability.

Abstract

Degenerate neutrino masses are excluded by experiment. The experimentally measured mass squared differences together with the yet undetermined absolute neutrino mass scale allow for a quasi-degenerate mass spectrum. For the lightest neutrino mass larger than roughly 0.1 eV, we analyse the influence of threshold corrections at the electroweak scale. We show that typical one-loop corrections can generate the observed neutrino mixing as well as the mass differences starting from exactly degenerate masses at the tree-level. Those threshold corrections have to be explicitly flavour violating. Flavour diagonal, non-universal corrections are not sufficient to simultaneously generate the correct mixing and the mass differences. We apply the new insights to an extension of the Minimal Supersymmetric Standard Model with non-minimal flavour violation in the soft breaking terms and discuss the low-energy threshold corrections to the light neutrino mass matrix in that model.