Peccei-Quinn symmetry for Dirac seesaw and leptogenesis

TL;DR

This paper proposes an extension of the DFSZ axion model that explains small Dirac neutrino masses and the matter-antimatter asymmetry in the universe through heavy particle decays and suppressed Yukawa couplings.

Contribution

It introduces a novel mechanism linking Peccei-Quinn symmetry breaking to Dirac neutrino mass generation and leptogenesis within an extended DFSZ framework.

Findings

Successful generation of lepton asymmetry via heavy particle decays

Partial conversion of lepton asymmetry to baryon asymmetry

Suppressed Dirac neutrino Yukawa couplings explained by scalar vevs

Abstract

We extend the DFSZ invisible axion model to simultaneously explain small Dirac neutrino masses and cosmic matter-antimatter asymmetry. After the Peccei-Quinn and electroweak symmetry breaking, the effective Yukawa couplings of the Dirac neutrinos to the standard model Higgs scalar can be highly suppressed by the ratio of the vacuum expectation value of an iso-triplet Higgs scalar over the masses of some heavy gauge-singlet fermions, iso-doublet Higgs scalars or iso-triplet fermions. The iso-triplet fields can carry a zero or nonzero hypercharge. Through the decays of the heavy gauge-singlet fermions, iso-doublet scalars or iso-triplet fermions, we can obtain a lepton asymmetry in the left-handed leptons and an opposite lepton asymmetry in the right-handed neutrinos. Since the right-handed neutrinos do not participate in the sphaleron processes, the left-handed lepton asymmetry can be partially converted to a baryon asymmetry.