On the nature of the fourth generation neutrino and its implications

A bstract We consider the neutrino sector of a Standard Model with four generations. While the three light neutrinos can obtain their masses from a variety of mechanisms with or without new neutral fermions, fourth-generation neutrinos need at least one new relatively light right-handed neutrino. If...

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Bibliographic Details
Published in:The journal of high energy physics 2012-07, Vol.2012 (7), Article 30
Main Authors: Aparici, Alberto, Herrero-García, Juan, Rius, Nuria, Santamaria, Arcadi
Format: Article
Language:English
Subjects:
Astronomical models
Classical and Quantum Gravitation
Cosmology
Elementary Particles
Fermions
High energy physics
Leptons
Neutrinos
Physics
Physics and Astronomy
Quantum Field Theories
Quantum Field Theory
Quantum Physics
Relativity Theory
String Theory
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Summary:A bstract We consider the neutrino sector of a Standard Model with four generations. While the three light neutrinos can obtain their masses from a variety of mechanisms with or without new neutral fermions, fourth-generation neutrinos need at least one new relatively light right-handed neutrino. If lepton number is not conserved this neutrino must have a Majorana mass term whose size depends on the underlying mechanism for lepton number violation. Majorana masses for the fourth-generation neutrinos induce relative large two-loop contributions to the light neutrino masses which could be even larger than the cosmological bounds. This sets strong limits on the mass parameters and mixings of the fourth-generation neutrinos.
ISSN:1029-8479
1029-8479
DOI:10.1007/JHEP07(2012)030