Neutrino masses and mixings in a seesaw framework

TL;DR

This paper explores the implications of the seesaw mechanism for neutrino masses, analyzing how different assumptions about mass matrices affect the scale of heavy neutrinos and their compatibility with solar neutrino solutions.

Contribution

It provides a detailed calculation of heavy neutrino masses under specific hypotheses relating to Dirac mass matrices and mixing, connecting neutrino solutions to mass scales.

Findings

Vacuum oscillation solution implies heavy neutrino masses above unification scale for M_ν ~ M_u.

MSW solutions are compatible with the unification scale for M_ν ~ M_u.

Lightest heavy neutrino can be as light as 10^5 GeV.

Abstract

Assuming the seesaw mechanism for hierarchical neutrino masses, we calculate the heavy neutrino masses under the hypotheses that the mixing in the Dirac leptonic sector is similar to the quark mixing ($V_D \sim V_{CKM}$) and that $M_{\nu} \sim M_u$ or $M_e$, where $M_{\nu}$ is the Dirac mass matrix of neutrinos. As a result we find that for $M_{\nu} \sim M_u$ the vacuum oscillation solution of the solar neutrino problem leads to a scale for the heavy neutrino mass well above the unification scale, while for the MSW solutions there is agreement with this scale. For $M_{\nu} \sim M_e$ the vacuum solution is consistent with the unification scale, and the MSW solutions with an intermediate scale. The mass of the lightest heavy neutrino can be as small as $10^5$ GeV.