Axiogenesis with a Heavy QCD Axion

TL;DR

This paper proposes that a heavy QCD axion, with a mass between 1 MeV and 10 GeV, can explain the matter-antimatter asymmetry in the universe through a rotation mechanism, linking cosmology and experimental searches.

Contribution

It introduces a novel mechanism where a heavy QCD axion's field rotation generates baryon asymmetry, expanding the viable parameter space for axion models beyond traditional expectations.

Findings

Heavy QCD axion with mass 1 MeV to 10 GeV can produce the observed matter-antimatter asymmetry.

The proposed mechanism links axion dynamics to sphaleron processes in the early universe.

Parameter space is accessible to current and future accelerator experiments and CMB observations.

Abstract

We demonstrate that the observed cosmological excess of matter over antimatter may originate from a heavy QCD axion that solves the strong CP problem but has a mass much larger than that given by the Standard Model QCD strong dynamics. We investigate a rotation of the heavy QCD axion in field space, which is transferred into a baryon asymmetry through weak and strong sphaleron processes. This provides a strong cosmological motivation for heavy QCD axions, which are of high experimental interest. The viable parameter space has an axion mass $m_a$ between 1~MeV and 10 GeV and a decay constant $f_a < 10^5$ GeV, which can be probed by accelerator-based direct axion searches and observations of the cosmic microwave background.