Primordial Dirac Leptogenesis

Abstract

We present a novel realization of Dirac leptogenesis based on the post-inflationary reheating phase of the early universe. An asymmetry generated within the scalar sector via CP-violating and out-of-equilibrium inflaton decays is transferred to chiral neutrinos through Yukawa interactions and then to baryons via electroweak sphalerons. We describe in detail a minimal realization of this mechanism that naturally accommodates small neutrino Yukawa couplings and results in contributions to the effective number of relativistic species, $N_{\text{eff}}$, testable in upcoming cosmological observations.