Minimal scoto-seesaw mechanism with spontaneous CP violation

TL;DR

This paper introduces a minimal scoto-seesaw model with spontaneous CP violation, linking dark matter stability and neutrino masses through a discrete symmetry, and predicts observable CP-violating effects in neutrino experiments.

Contribution

It presents a simple model combining dark matter stability and neutrino mass generation with spontaneous CP violation using a single $ ext{Z}_8$ symmetry.

Findings

Predicts Dirac CP phase within current experimental sensitivity.

Links neutrino mass scale to cosmological and double beta decay constraints.

Shows spontaneous CP violation can be naturally incorporated into minimal models.

Abstract

We propose simple scoto-seesaw models to account for dark matter and neutrino masses with spontaneous CP violation. This is achieved with a single horizontal $\mathcal{Z}_8$ discrete symmetry, broken to a residual $\mathcal{Z}_2$ subgroup responsible for stabilizing dark matter. CP is broken spontaneously via the complex vacuum expectation value of a scalar singlet, inducing leptonic CP-violating effects. We find that the imposed $\mathcal{Z}_8$ symmetry pushes the values of the Dirac CP phase and the lightest neutrino mass to ranges already probed by ongoing experiments, so that normal-ordered neutrino masses can be cornered by cosmological observations and neutrinoless double beta decay experiments.