3-Neutrino Mass Spectrum from Combining Seesaw and Radiative Neutrino Mass Mechanisms

TL;DR

This paper presents a model extending the Standard Model with additional Higgs and neutrino singlet fields, naturally explaining the neutrino mass hierarchy and oscillation phenomena through combined seesaw and radiative mechanisms.

Contribution

It introduces a novel framework combining seesaw and radiative mechanisms to generate the full neutrino mass spectrum without requiring symmetries.

Findings

Successfully reproduces neutrino mass hierarchy and mixing angles

Explains atmospheric and solar neutrino oscillations within the model

Provides a natural explanation for the smallness of neutrino masses

Abstract

We extend the Standard Model by adding a second Higgs doublet and a right-handed neutrino singlet with a heavy Majorana mass term. In this model, there are one heavy and three light Majorana neutrinos with a mass hierarchy m_3 >> m_2 >> m_1 such that that only m_3 is non-zero at the tree level and light because of the seesaw mechanism, m_2 is generated at the one-loop and m_1 at the two-loop level. We show that the atmospheric neutrino oscillations and large mixing MSW solar neutrino transitions with $\Delta m^2_\mathrm{atm} \simeq m_3^2$ and $\Delta m^2_\mathrm{solar} \simeq m_2^2$, respectively, are naturally accommodated in this model without employing any symmetry.