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.
Highlights
The explanation of the observed baryon-to-photon ratio is one of the most fascinating and important questions of fundamental physics since it is directly linked to the origin of our exis-T
The underlying conditions for successful baryogenesis formulated by Sakharov [1] allow for a wide variety of models, among which leptogenesis [2] is of special interest because it establishes a connection between the baryon asymmetry of the Universe (BAU) and the generation of light active neutrino masses
We investigated leptogenesis and low-energy CP violation in the context of a left-right-symmetric seesaw model
Summary
Working in the parameter region where the type-II contribution dominates leptogenesis and neutrino mass, the diagram that generates the lepton asymmetry is the decay of the triplet with a vertex correction involving right-handed neutrinos. This, in turn, allows for a careful and robust analysis of the dependence of the baryon asymmetry on measurable low-energy parameters, in particular, the mass ordering, the CP phase δ, and the effective neutrino mass mee that is crucial for neutrinoless double beta decay. This paper is structured as follows: Sec. 2 summarizes the generation of neutrino mass in the minimal mixed type-(I+II) seesaw model and the simplifications brought about by a dominating triplet contribution. Various technical details are collected in a number of appendices
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