Leptogenesis in cosmological relaxation with particle production

Abstract

Cosmological relaxation of the electroweak scale is improved by using particle production to trap the relaxion. We combine leptogenesis with such a relaxion model that has no extremely small parameters or large e-foldings. Scanning happens after inflation - now allowed to be at a high scale - over a sub-Planckian relaxion field range for a cutoff scale of new physics up to O(100) TeV. Particle production by the relaxion also reheats the universe and generates the baryonic matter-antimatter asymmetry. We propose a realization in which out-of-equilibrium leptons, produced by the relaxion, scatter with the thermal bath through interactions that violate CP and lepton number via higher-dimensional operators. Such a minimal effective field theory setup, with no new physics below the cutoff, naturally decouples new physics while linking leptogenesis to relaxion particle production; the baryon asymmetry of the universe can thus be intrinsically tied to a weak scale hierarchy.