Wash-In Leptogenesis

TL;DR

Wash-in leptogenesis is a novel mechanism within the type-I seesaw model that generates baryon asymmetry at relatively low neutrino masses without requiring CP violation, by leveraging nonminimal cosmological backgrounds and chemical potential reprocessing.

Contribution

It introduces wash-in leptogenesis, a new approach that operates at lower scales and does not need CP violation, expanding the landscape of baryogenesis models.

Findings

Operates at right-handed neutrino masses of a few 100 TeV.

Does not require CP violation in the neutrino sector.

Applicable in strong wash-out regimes.

Abstract

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 100 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.