Implications of new generations on neutrino masses

TL;DR

This paper investigates how additional fermion generations at the LHC could naturally explain small neutrino masses through two-loop radiative mechanisms within an extended Standard Model.

Contribution

It introduces a model with two extra fermion generations and analyzes how this setup can account for neutrino masses and mixings while respecting cosmological bounds.

Findings

One extra generation cannot fit observed neutrino data.

Two extra generations can produce acceptable neutrino masses.

Model predicts specific phenomenological signals at colliders.

Abstract

We explore the possible implications that new families, that are being searched for at the LHC, would have on neutrino masses. In particular, we have explored the possibility that the smallness of the observed neutrino masses is naturally understood in a modified version of the Standard Model (SM) with complete extra generations of fermions, i.e., that have right-handed neutrinos, in which neutrino masses are generated at two loops. With one extra family it is not possible to fit the observed spectrum of masses and mixings. However, the radiative mass generated provides an important constraint in these kind of models, so the neutrino masses do not exceed their cosmological bound. Within the context of two extra families, we analyse the allowed parameter space and the possible phenomenological signals. Contribution to NUFACT 11, XIIIth International Workshop on Neutrino Factories, Super beams and Beta beams, 1-6 August 2011, CERN and University of Geneva (Submitted to IOP conference series).