Low Energy Signatures of the TeV Scale See-Saw Mechanism

TL;DR

This paper explores a low-energy TeV scale see-saw mechanism where heavy right-handed neutrinos could be produced at the LHC, but current experimental bounds strongly constrain their observable signatures across various experiments.

Contribution

It demonstrates the correlations between neutrino Yukawa couplings and low-energy neutrino parameters, and analyzes the experimental constraints on detecting heavy neutrinos and related phenomena.

Findings

Heavy neutrinos are difficult to observe at the LHC due to current bounds.

Neutrinoless double beta decay rates could be enhanced within experimental sensitivity.

The $ ext{BR}( ext{mu} o e + ext{gamma})$ could be within MEG experiment sensitivity.

Abstract

We study a type I see-saw scenario where the right-handed (RH) neutrinos, responsible for the light neutrino mass generation, lie at the electroweak scale. Under certain conditions, the strength of the charged and neutral current weak interactions of the Standard Model particles with the heavy RH neutrinos can be large enough to allow their production at the LHC, opening also the possibility of observing other low energy signatures of the new physics in the electroweak precision observables as well as in searches for rare leptonic decays or neutrinoless double beta decay. We argue that in this scenario the flavour structure of the neutrino Yukawa couplings is essentially determined by the low energy neutrino parameters, leading to fairly strong correlations among the new phenomena. In particular, we show that the present bound on the $\mu \to e +\gamma$ decay rate makes very difficult the observation of the heavy RH neutrinos at the LHC or the observation of deviations from the Standard Model predictions in the electroweak precision data. We also argue that all present experimental constraints on this scenario still allow i) for an enhancement of the rate of neutrinoless double beta decay, which thus can be in the range of sensitivity of the GERDA experiment even when the light Majorana neutrinos possess a normal hierarchical mass spectrum, and ii) for the predicted $\mu \to e+ \gamma$ decay rate to be within the sensitivity range of the MEG experiment.