An Updated Numerical Analysis of eV Seesaw with Four Generations

TL;DR

This paper updates the numerical analysis of the eV-scale seesaw model extended to four generations, examining implications for neutrino mixing, CP violation, and sterile neutrino constraints with recent experimental data.

Contribution

It provides a novel four-generation extension of the eV seesaw model and updates previous analyses with recent experimental results, especially regarding sterile neutrinos and mixing angles.

Findings

Current data do not strongly constrain models with more than one sterile neutrino.

The four-generation model naturally includes three active and three sterile neutrinos.

Implications for the third mixing angle and CP violation are analyzed.

Abstract

We consider the so-called "eV seesaw" scenario, with right-handed Majorana mass $M_R$ at eV order, extended to four lepton generations. The fourth generation gives a heavy pseudo-Dirac neutral lepton, which largely decouples from other generations and is relatively stable. The framework naturally gives 3 active and 3 sterile neutrinos. We update a previous numerical analysis of a 3+3 study of the LSND anomaly, taking into account the more recent results from the MiniBooNE experiment. In particular, we study the implications for the third mixing angle $\mathrm{sin}^2\theta_{13}$, as well as CP violation. We find that current data do not seriously constrain more than one sterile neutrinos.