Neutrino in Standard Model and beyond

TL;DR

This paper reviews the role of neutrinos within the Standard Model and explores the implications of their Majorana masses, emphasizing the significance of lepton-number violation and potential experimental evidence like neutrinoless double beta decay.

Contribution

It provides a detailed analysis of neutrino mass generation via Majorana terms and discusses the minimal scenario consistent with Standard Model principles and experimental constraints.

Findings

Majorana neutrino masses are suppressed relative to other fermions.

Neutrinoless double beta decay would support the Majorana neutrino hypothesis.

Absence of sterile neutrino transitions aligns with the minimal scenario.

Abstract

After discovery of the Higgs boson at CERN the Standard Model acquired a status of the theory of the elementary particles in the electroweak range (up to about 300 GeV). What general conclusions can be inferred from the Standard Model? It looks that the Standard Model teaches us that in the framework of such general principles as local gauge symmetry, unification of weak and electromagnetic interactions and Brout-Englert-Higgs spontaneous breaking of the electroweak symmetry nature chooses the simplest possibilities. Two-component left-handed massless neutrino fields play crucial role in the determination of the charged current structure of the Standard Model. The absence of the right-handed neutrino fields in the Standard Model is the simplest, most economical possibility. In such a scenario Majorana mass term is the only possibility for neutrinos to be massive and mixed. Such mass term is generated by the lepton-number violating Weinberg effective Lagrangian. In this approach three Majorana neutrino masses are suppressed with respect to the masses of other fundamental fermions by the ratio of the electroweak scale and a scale of a lepton-number violating physics. The discovery of the neutrinoless double $\beta$-decay and absence of transitions of flavor neutrinos into sterile states would be evidence in favor of the minimal scenario we advocate here.