Leptoflavorgenesis: baryon asymmetry of the Universe from lepton flavor violation

TL;DR

This paper proposes a novel mechanism called leptoflavorgenesis, where charged-lepton flavor violation processes in the early Universe generate lepton flavor asymmetries that are converted into the observed baryon asymmetry, linking low-energy CLFV to cosmological matter-antimatter imbalance.

Contribution

It introduces the concept of leptoflavorgenesis, demonstrating how efficient CLFV interactions can produce the baryon asymmetry through lepton flavor asymmetries and weak sphaleron processes.

Findings

Two-loop corrections imply lepton flavor asymmetries can generate baryon asymmetry.

Leptoflavorgenesis scenarios explain the small baryon-to-photon ratio.

Conversion factor is suppressed by charged-lepton Yukawa couplings squared.

Abstract

Charged-lepton flavor violation (CLFV) is a smoking-gun signature of physics beyond the Standard Model. The discovery of CLFV in upcoming experiments would indicate that CLFV processes must have been efficient in the early Universe at relatively low temperatures. In this letter, we point out that such efficient CLFV interactions open up new ways of creating the baryon asymmetry of the Universe. First, we quote the two-loop corrections from charged-lepton Yukawa interactions to the chemical transport in the Standard Model plasma, which imply that nonzero lepton flavor asymmetries summing up to $B-L = 0$ are enough to generate the baryon asymmetry. Then, we describe two scenarios of what we call {\it leptoflavorgenesis}, where efficient CLFV processes are responsible for the generation of primordial lepton flavor asymmetries that are subsequently converted to a baryon asymmetry by weak sphaleron processes. Here, the conversion factor from lepton flavor asymmetry to baryon asymmetry is suppressed by charged-lepton Yukawa couplings squared, which provides a natural explanation for the smallness of the observed baryon-to-photon ratio.