Leptogenesis with Lepton-Number-Violating Dirac Neutrinos

TL;DR

This paper proposes a novel leptogenesis mechanism involving lepton-number-violating Dirac neutrinos, where scalar decay generates asymmetry that is converted to baryons, explaining small neutrino masses and affecting early universe degrees of freedom.

Contribution

It introduces a new leptogenesis model with gauged B-L symmetry and a neutrinophilic two-Higgs-doublet, linking neutrino mass generation to baryon asymmetry.

Findings

Decay of a new scalar creates right-handed neutrino asymmetry.

Model predicts an effective relativistic degrees of freedom N(eff) = 3.29.

Provides a natural explanation for small neutrino masses.

Abstract

Dirac neutrinos with lepton-number-violating interactions can give rise to a new leptogenesis mechanism. In its simplest renormalizable realization, based on a gauged B-L symmetry spontaneously broken by four units, the decay of a new scalar creates an asymmetry in the right-handed neutrinos. A neutrinophilic two-Higgs-doublet model converts this asymmetry to the baryons, provides a natural explanation of the small neutrino masses, and can lead to an effective number of relativistic degrees of freedom of N(eff) = 3.29 due to the entropy-suppressed contribution of the right-handed neutrinos.