A Common Origin of Asymmetric Self-interacting Dark Matter and Dirac Leptogenesis

TL;DR

This paper proposes a unified framework linking asymmetric self-interacting dark matter with Dirac leptogenesis, explaining baryon asymmetry and dark matter properties through new particles and symmetries.

Contribution

It introduces a novel model connecting dark matter asymmetry and leptogenesis via heavy scalar decays and extended gauge symmetries, with implications for dark matter detection.

Findings

Heavy scalar decay generates B-L asymmetry in neutrinos.

Dark matter self-interactions mediated by a Z' boson.

Model predicts detectable signals in dark matter experiments.

Abstract

Assuming dark matter to be asymmetric as well as self-interacting and neutrinos to be Dirac fermions, we propose a framework to address the observed baryon imbalance of the universe. We add three right-handed neutrinos $\nu_{R_i},\,{i=1,2,3}$, one singlet fermion $\chi$, a doublet fermion $\psi$, and heavy scalar doublets $\eta_i,\,{i=1,2}$ to the Standard Model. A global $B-L$ is imposed to protect the Dirac nature of neutrinos. Both $\chi$ and $\psi$ are fermions with non-zero charge under an extended $U(1)_{B-L} \times U(1)_D$ symmetry. Additionally, a $\mathcal{Z}_2$ symmetry is imposed, where the singlets $\chi$, $\nu_R$, and $\eta$ are negative and the doublet $\psi$ is positive. The CP-violating out-of-equilibrium decay of heavy scalar $\eta$ generates an equal and opposite $B-L$ asymmetry among the left-handed ($\nu_L$) and right-handed ($\nu_R$) neutrinos. The $\nu_L-\nu_R$ equilibration process does not take place until below the Electroweak phase transition scale because of tiny Yukawa couplings. During this time, Sphaleron processes, which are active at temperatures higher than 100 GeV, transform a portion of the $B-L$ asymmetry stored in left-handed neutrinos into baryon asymmetry. MeV scale gauge boson $Z'$ of $U(1)_D$ sector mediates both annihilation of symmetric dark matter component and self-interaction among dark matter particles. Moreover, $Z'$ mixes with the Standard Model Z-boson and provides a portal for dark matter direct detection.