The Minimal UV-induced Effective QCD Axion Theory

TL;DR

This paper proposes minimal UV-induced effective theories for QCD axions, linking high-scale symmetry breaking to observable axion couplings and suggesting experimental tests for these models.

Contribution

It introduces three minimal natural scenarios connecting QCD axions with high-scale mediators, expanding the understanding of axion origins and potential detection methods.

Findings

PQ symmetry breaking scale around 10^{15} GeV

Higher than classical axion dark matter window

Proposes an experiment to test these scenarios

Abstract

The characteristic axion couplings could be generated via effective couplings between the Standard Model (SM) fermions to a pseudo-Goldstone from a high-scale $U(1)$ Peccei-Quinn (PQ) symmetry breaking. Assuming that the UV-induced effective operators generate necessary couplings before the PQ symmetry breaking, and any low-scale couplings to the SM are restricted to the Yukawa sector, three minimal natural scenarios can be formulated, which provides a connection between the QCD-axions and mediators at the GUT/string scales. We find that the PQ symmetry breaking scale could be about $10^{15}$ GeV, higher than the classical QCD dark matter axion window but possible if the anthropic window is considered. We also propose an experiment to probe such scenarios. If the dark matter axion is discovered, they might suggest that we live in an atypical Hubble volume.