Baryon Asymmetry of the Universe from Lepton Flavor Violation

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 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.

Automated summary

Charged-lepton flavor violation (CLFV) is a distinct feature of physics beyond the standard model, which plays an important role in the early universe. This Letter points out that efficient CLFV interactions create new pathways for generating the baryon asymmetry of the universe, and the conversion factor from lepton flavor asymmetry to baryon asymmetry is naturally explained by the suppression of charged-lepton Yukawa couplings squared.