Low-scale leptogenesis with three heavy neutrinos

TL;DR

This paper explores low-scale leptogenesis with three heavy neutrinos, revealing new behaviors due to lepton number violation, flavor effects, and matter resonances, making the scenario testable by current experiments.

Contribution

It extends previous two-neutrino models to three neutrinos, uncovering new phenomena and conditions for efficient, testable leptogenesis at low scales.

Findings

Lepton number violating oscillations and decays are significant.

Resonant enhancement due to matter effects improves leptogenesis efficiency.

Large heavy neutrino mixing angles near experimental limits enable testable predictions.

Abstract

Leptogenesis induced by the oscillations of GeV-scale neutrinos provides a minimal and testable explanation of the baryon asymmetry of the Universe. In this work we extend previous studies invoking only two heavy neutrinos to the case of three heavy neutrinos. We find qualitatively new behaviour as a result of lepton number violating oscillations and decays, strong flavour effects in the washout and a resonant enhancement due to matter effects. An approximate global $B - \bar L$ symmetry (representing the difference of baryon and a generalised lepton number) can protect the light neutrino masses from large radiative corrections, while simultaneously providing the ingredients for the resonant enhancement of the lepton asymmetry due to thermal contributions to the heavy neutrino dispersion relations. This mechanism is particularly efficient for large heavy neutrino mixing angles near the current experimental limits, a regime in which leptogenesis is not feasible in the minimal scenario with two heavy neutrinos. In this new parameter regime, low-scale leptogenesis is testable by the LHC and other existing experiments.