Conformal Neutrinos: an Alternative to the See-saw Mechanism

TL;DR

This paper proposes a conformal field theory framework for neutrino masses, predicting naturally small Dirac masses and potential observable effects in Higgs decays, with implications for sterile neutrinos and neutrino oscillations.

Contribution

It introduces a novel conformal neutrino model where right-handed neutrinos acquire anomalous dimensions, leading to suppressed Yukawa couplings and new phenomenological signatures.

Findings

Small neutrino masses naturally arise from conformal suppression.

Higgs invisible decay channels could be significantly enhanced.

Light sterile neutrinos may be detectable in oscillation experiments.

Abstract

We analyze a scenario where the right-handed neutrinos make part of a strongly coupled conformal field theory and acquire an anomalous dimension \gamma<1 at a large scale \Lambda. Their Yukawa couplings to the Higgs become irrelevant at the fixed point and they are suppressed at low scales giving rise naturally to a small (sub-meV) Dirac neutrino mass which breaks the conformal invariance. We derive an upper bound on \gamma from loop-induced flavor changing neutral currents. Neutrino Yukawa couplings can be sizable at electroweak scales and therefore the invisible decay of the Higgs in the neutrino channel can be comparable to the c\bar c and \tau\bar\tau modes and predict interesting Higgs phenomenology. If lepton number is violated in the conformal theory an irrelevant Majorana mass operator for right-handed neutrinos appears for \gamma>1/2 giving rise to an inverse see-saw mechanism. In this case light sterile neutrinos do appear and neutrino oscillation experiments are able to probe our model.