Nearly degenerate neutrinos, Supersymmetry and radiative corrections

TL;DR

This paper explores how nearly degenerate neutrinos within the MSSM framework, affected by radiative corrections, can naturally explain atmospheric and large angle MSW solar neutrino oscillations, but not vacuum oscillations.

Contribution

It demonstrates that radiative corrections in the MSSM with see-saw neutrino masses can generate the observed neutrino oscillation parameters, providing a natural hierarchy of mass splittings.

Findings

Radiative corrections produce mass splittings compatible with atmospheric and solar neutrino data.

Vacuum oscillation solution to solar neutrinos is excluded in this scenario.

Implications for triviality limits, Yukawa couplings, and unification are discussed.

Abstract

If neutrinos are to play a relevant cosmological role, they must be essentially degenerate with a mass matrix of the bimaximal mixing type. We study this scenario in the MSSM framework, finding that if neutrino masses are produced by a see-saw mechanism, the radiative corrections give rise to mass splittings and mixing angles that can accommodate the atmospheric and the (large angle MSW) solar neutrino oscillations. This provides a natural origin for the $\Delta m^2_{sol} << \Delta m^2_{atm}$ hierarchy. On the other hand, the vacuum oscillation solution to the solar neutrino problem is always excluded. We discuss also in the SUSY scenario other possible effects of radiative corrections involving the new neutrino Yukawa couplings, including implications for triviality limits on the Majorana mass, the infrared fixed point value of the top Yukawa coupling, and gauge coupling and bottom-tau unification.