On the Interplay Between the 'Low' and 'High' Energy CP-Violation in Leptogenesis

TL;DR

This paper explores how low-energy neutrino mixing and high-energy neutrino interactions contribute to CP-violation in leptogenesis, showing that successful baryon asymmetry can be achieved mainly through low-energy phases.

Contribution

It demonstrates that in hierarchical type I see-saw models, low-energy CP-violating phases can dominate leptogenesis even when high-energy phases are large but subdominant.

Findings

Low-energy CP-violation can suffice for successful leptogenesis.

High-energy phases may be large but have a suppressed role.

Majorana phases in neutrino mixing are crucial for baryon asymmetry.

Abstract

The CP-violation necessary for the generation of the baryon asymmetry of the Universe in the "flavoured" leptogenesis scenario can arise from the "low energy" PMNS neutrino mixing matrix and/or from the "high energy" part of neutrino Yukawa couplings, which can mediate CP-violating phenomena only at some high energy scale. The possible interplay between these two types of CP-violation is discussed. The type I see-saw model with three heavy right-handed Majorana neutrinos having hierarchical spectrum is considered. The analysis shows that there exist regions in the leptogenesis parameter space where the relevant "high energy" phases have large CP-violating values, but the purely "high energy" contribution to the baryon asymmetry plays a subdominant/suppressed role in the production of baryon asymmetry compatible with the observations and one can have successful leptogenesis if the requisite CP-violation is provided by the Majorana phase(s) in the neutrino mixing matrix.