Wash-In Leptogenesis

We present a leptogenesis mechanism based on the standard type-I seesaw model that successfully operates at right-handed-neutrino masses as low as a few hundred TeV. This mechanism, which we dub wash-in leptogenesis, does not require any CP violation in the neutrino sector and can be implemented even in the regime of strong wash-out. The key idea behind wash-in leptogenesis is to generalize standard freeze-out leptogenesis to a nonminimal cosmological background in which the chemical potentials of all particles not in chemical equilibrium at the temperature of leptogenesis are allowed to take arbitrary values. This sets the stage for building a plethora of new baryogenesis models where chemical potentials generated at high temperatures are reprocessed to generate a nonvanishing B - L asymmetry at low temperatures. As concrete examples, we discuss wash-in leptogenesis after axion inflation and in the context of grand unification.

Automated summary

This mechanism, wash-in leptogenesis, operates at low masses of right-handed neutrinos without requiring CP violation, even in the regime of strong wash-out. By generalizing standard freeze-out leptogenesis to a nonminimal cosmological background, it allows for the generation of a nonvanishing B - L asymmetry using chemical potentials generated at high temperatures.