Vacuum Stability Constraints on the Minimal Singlet TeV Seesaw Model

TL;DR

This paper investigates how vacuum stability constraints limit the coupling strength in a minimal TeV-scale singlet neutrino model, with implications for lepton flavor violation, neutrinoless double beta decay, and collider signatures.

Contribution

It introduces vacuum stability bounds as a new constraint on the neutrino Yukawa coupling in the minimal singlet seesaw model, linking theoretical stability with experimental observables.

Findings

Yukawa coupling strength $y_\nu$ is constrained by vacuum stability bounds.

Lepton flavor violating decays like $\mu \rightarrow e \gamma$ further restrict $y_\nu$.

Implications for neutrinoless double beta decay and collider signals are discussed.

Abstract

We consider the minimal seesaw model in which two gauge singlet right handed neutrinos with opposite lepton numbers are added to the Standard Model. In this model, the smallness of the neutrino mass is explained by the tiny lepton number violating coupling between one of the singlets with the standard left-handed neutrinos. This allows one to have the right handed neutrino mass at the TeV scale as well as appreciable mixing between the light and heavy states. This model is fully reconstructible in terms of the neutrino oscillation parameters apart from the overall coupling strengths. We show that the overall coupling strength $y_\nu$ for the Dirac type coupling between the left handed neutrino and one of the singlets can be restricted by consideration of the (meta)stability bounds on the electroweak vacuum. In this scenario the lepton flavor violating decays of charged leptons can be appreciable which can put further constraint on $y_\nu$, for right-handed neutrinos at TeV scale. We discuss the combined constraints on $y_\nu$ for this scenario from the process $\mu \rightarrow e \gamma$ and from the consideration of vacuum (meta)stability constraints on the Higgs self coupling. We also briefly discuss the implications for neutrinoless double beta decay and possible signatures of the model that can be expected at colliders.