Leptogenesis in Cosmological Relaxation with Particle Production

TL;DR

This paper proposes a model where the relaxion mechanism, aided by particle production, simultaneously addresses the electroweak hierarchy problem and generates the universe's matter-antimatter asymmetry through leptogenesis, all within a minimal effective field theory.

Contribution

It introduces a novel framework combining cosmological relaxation with leptogenesis via particle production, avoiding extremely small parameters and large e-foldings, and linking baryogenesis to the weak scale hierarchy.

Findings

Reheating of the universe through relaxion-induced particle production.

Generation of baryon asymmetry via out-of-equilibrium leptons and higher-dimensional operators.

A minimal effective field theory setup connecting leptogenesis to the relaxion mechanism.

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 an $\mathcal{O}(100)$ TeV cut-off scale of new physics. Particle production by the relaxion also reheats the universe and generates the baryonic matter-antimatter asymmetry. We propose a realisation 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 cut-off, 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.