The Minimal Extension of the SM and the Neutrino Oscillation Data

TL;DR

This paper examines the minimal extension of the Standard Model with one right-handed neutrino, analyzing two neutrino mass schemes and their ability to explain solar and atmospheric neutrino anomalies, with testable predictions for BOREXINO.

Contribution

It identifies the conditions under which the minimal model can explain neutrino oscillation data and highlights the limitations of this minimal extension.

Findings

Scheme II can explain both atmospheric and solar neutrino anomalies.

The minimal extension cannot account for bi-maximal mixing or dark matter.

The model's predictions are testable in the BOREXINO experiment.

Abstract

We study the simplest Standard Model estension with only one extra right-handed neutrino. In this case there are two massless $m_{1,2}$ and two massive $m_{3,4}$ neutrinos, and in principle both solar and atmospheric anomalies can be described in two different scenarios, $m_3 << m_4$ (scheme I) and $m_3 \simeq m_4$ (scheme II). However, neither bi-maximal mixing nor the dark matter problem are explained in this minimal extension. Only scheme II can accommodate simultaneously maximal mixing for atmospheric neutrinos and the small mixing angle MSW solution for the solar anomaly. This scenario can be tested in the BOREXINO experiment.