Electromagnetic Dirac Cogenesis

TL;DR

This paper introduces a new cogenesis mechanism where heavy vector-like fermions decay into dark matter and neutrinos, generating asymmetries that explain dark matter abundance and baryon asymmetry, with testable implications for experiments and cosmology.

Contribution

It presents a novel electromagnetic dipole-mediated cogenesis model linking dark matter and neutrino asymmetries with fixed dark matter mass and observable signatures.

Findings

Dark matter asymmetry is generated via heavy fermion decay.

Dark matter mass is constrained to around 1 GeV.

Model predicts observable signals in gamma-ray telescopes and CMB experiments.

Abstract

We propose a novel cogenesis mechanism by utilising the two-body decay of heavy vector-like fermions to dark matter (DM) $\chi$ and right chiral part of light Dirac neutrino $\nu_R$ via the electromagnetic dipole operator. This leads to generation of asymmetry in dark fermion $\chi$ as well as $\nu_R$ with the latter getting transferred to left-handed lepton doublets via Yukawa interactions with a neutrinophilic Higgs doublet. While lepton asymmetry is converted into baryon asymmetry of the Universe via electroweak sphalerons, the dark fermion asymmetry results in asymmetric dark matter. Since CP asymmetries in lepton and dark sector are equal and opposite due to net lepton number conservation, DM mass is restricted to a fixed value $\sim \mathcal{O}(1)$ GeV. Long-lived nature of DM keeps indirect detection prospects at gamma-ray telescopes alive while thermalised light Dirac neutrinos lead to observable dark radiation at cosmic microwave background (CMB) experiments. Heavy vector-like fermions can be probed at terrestrial experiments via their electromagnetic dipole interactions.