Co-genesis of Matter and Dark Matter with Vector-like Fourth Generation Leptons

TL;DR

This paper introduces a model extending the Standard Model with a vector-like fourth-generation lepton doublet, proposing a novel inelastic dark matter candidate produced via scalar triplet decay, linking dark matter and baryon asymmetry.

Contribution

It presents a minimal extension with a fourth-generation neutrino as inelastic dark matter, connecting dark matter relic abundance and baryogenesis through scalar triplet decay.

Findings

The fourth neutrino can be a viable inelastic dark matter candidate.

Relic abundance is generated via CP-violating decay of scalar triplet.

The model links neutrino masses, dark matter, and baryon asymmetry.

Abstract

We propose a simple extension of the standard model by adding a fourth generation vector-like lepton doublet and show that if the fourth neutrino is a massive pseudo-Dirac fermion with mass in the few hundred GeV range and mass splitting of about 100 keV, its lighter component can be a viable inelastic dark matter candidate. Its relic abundance is produced by the CP violating out-of-equilibrium decay of the type-II seesaw scalar triplet, which also gives rise to the required baryon asymmetry of the Universe via type-II leptogenesis, thus providing a simultaneous explanation of dark matter and baryon abundance observed today. Moreover, the induced vacuum expectation value of the same scalar triplet is responsible for the sub-eV Majorana masses to the three active neutrinos. A stable fourth generation of neutrinos is elusive at collider, however might be detected by current dark matter direct search experiments.