Testing quasi-Dirac leptogenesis through neutrino oscillations

TL;DR

This paper explores how quasi-Dirac neutrinos, arising from small lepton number violation, can simultaneously explain neutrino oscillations and generate the universe's matter-antimatter asymmetry through resonant leptogenesis.

Contribution

It demonstrates that the parameter space for successful leptogenesis overlaps with that of observable neutrino oscillations, linking high-scale baryogenesis to low-scale neutrino experiments.

Findings

Quasi-Dirac neutrinos can enhance CP violation in heavy fermion decays.

The viable leptogenesis parameter space aligns with solar and atmospheric neutrino oscillation regimes.

Small neutrino mass splittings from quasi-Diracness are testable in oscillation experiments.

Abstract

The lightness of the Standard Model (SM) neutrinos could be understood if their masses were to be generated by new physics at a high scale, through the so-called seesaw mechanism involving heavy fermion singlets. If new physics violates baryon minus lepton number by only a small amount, the heavy fermion singlets as well as the SM neutrinos split into pairs of quasi-Dirac states. At the scale of the fermion singlets, this quasi-Diracness allows to enhance CP violation in their decays and the cosmic matter-antimatter asymmetry can be successfully generated through resonant leptogenesis. At lower scale, this quasi-Diracness results in small SM neutrino mass splitting which can be probed in oscillation experiments. Remarkably, the parameter space for viable leptogenesis spans over the regime relevant for solar and atmospheric neutrino oscillations.