Leptogenesis from left-handed neutrino production during axion inflation

We propose that the observed matter-antimatter asymmetry can be naturally produced as a byproduct of axion-driven slow-roll inflation by coupling the axion to standard-model neutrinos. We assume that GUT scale right-handed neutrinos are responsible for the masses of the standard model neutrinos and that the Higgs field is light during inflation and develops a Hubble scale vacuum expectation value (VEV). In this set up, the rolling axion generates a helicity asymmetry in standard-model neutrinos. Following inflation, this helicity asymmetry becomes equal to a net lepton number as the Higgs VEV decays and is partially re-processed by the $SU(2)_{L}$ sphaleron into a net baryon number.