Out-of-the-box Baryogenesis During Relaxation

TL;DR

This paper demonstrates that relaxion models can naturally produce the observed baryon asymmetry through spontaneous baryogenesis during slow roll, linking it to relaxion parameters and dark matter candidates.

Contribution

It introduces a novel mechanism for baryogenesis within relaxion models, connecting it to the relaxion's properties and the dark matter parameter space.

Findings

Baryon asymmetry can be generated during relaxion slow roll.

Successful baryogenesis occurs for relaxion masses between 10^{-10} and 10^{-5} eV.

The mechanism is compatible with relaxion dark matter scenarios.

Abstract

We show that spontaneous baryogenesis occurs automatically in relaxion models if the reheating temperature is larger than the weak scale, provided the Standard Model fields are charged under the U(1) of which the relaxion is a pseudo-Nambu-Goldstone boson. During the slow roll, the relaxion breaks CPT, biasing the thermal equilibrium in favor of baryons, with sphalerons providing the necessary baryon number violation. We calculate the resulting baryon asymmetry, explore the possible constraints on this scheme and show that there is a swath of parameter space in which the current observations are matched. Successful baryogenesis can be achieved for a range of relaxion masses between $10^{-10}$ and $10^{-5}$ eV. The mechanism operates precisely in the region of parameter space where recent work has shown relaxion oscillations to be a dark matter candidate.