Leptogenesis and low-energy CP violation in a type-II-dominated left-right seesaw model

TL;DR

This paper investigates leptogenesis within a minimal left-right symmetric seesaw model dominated by type-II contributions, linking low-energy CP violation to the baryon asymmetry with limited flavor effects.

Contribution

It introduces a predictive minimal model where low-energy phases drive leptogenesis, emphasizing the role of a single dominant Dirac mass matrix entry and analyzing flavor effects.

Findings

Successful baryon asymmetry generation in the model

Limited impact of flavor effects on leptogenesis

Implications for low-energy CP violation and neutrinoless double beta decay

Abstract

We consider leptogenesis in a left-right-symmetric seesaw scenario in which neutrino mass generation and leptogenesis are dominated by the type-II seesaw term. Motivated by grand unification, we assume that the neutrino Dirac mass matrix is dominated by a single entry of the order of the top-quark mass, which leaves the low-energy phases of the lepton mixing matrix as the only sources of CP violation. Working in a regime where the triplet scalar predominantly decays into leptons, this results in a predictive scenario based on a minimal number of parameters. We perform a detailed analysis of the flavored Boltzmann equations within a revised density matrix framework and demonstrate that the observed baryon asymmetry can be successfully generated in this simple model. We point out that the significance of flavor effects is limited, and we discuss the implications for low-energy observables such as the Dirac CP phase and neutrinoless double beta decay.