# Neutrino Mass, Dark Matter and Baryon Asymmetry without Lepton Number Violation

## TL;DR

This paper introduces a TeV-scale model that explains neutrino masses, dark matter stability, and baryon asymmetry without lepton number violation, using a conserved lepton number and a $Z_2$ symmetry.

## Contribution

The model uniquely generates neutrino masses, dark matter stability, and baryogenesis mechanisms without requiring lepton number violation or extremely heavy particles.

## Key findings

- Neutrino masses are generated via $Z_2$-odd particles.
- Scalar dark matter satisfies abundance and direct search constraints.
- The model allows for a strong first-order phase transition for baryogenesis.

## Abstract

We propose a model to explain tiny masses of neutrinos with the lepton number conservation, where neither too heavy particles beyond the TeV-scale nor tiny coupling constants are required. Assignments of conserving lepton numbers to new fields result in an unbroken $Z_2$ symmetry that stabilizes the dark matter candidate (the lightest $Z_2$-odd particle). In this model, $Z_2$-odd particles play an important role to generate the mass of neutrinos. The scalar dark matter in our model can satisfy constraints on the dark matter abundance and those from direct searches. It is also shown that the strong first-order phase transition, which is required for the electroweak baryogenesis, can be realized in our model. In addition, the scalar potential can in principle contain CP-violating phases, which can also be utilized for the baryogenesis. Therefore, three problems in the standard model, namely absence of neutrino masses, the dark matter candidate, and the mechanism to generate baryon asymmetry of the Universe, may be simultaneously resolved at the TeV-scale. Phenomenology of this model is also discussed briefly.