# The QCD Axion and Unification

## TL;DR

This paper explores how a grand unified theory can predict the QCD axion mass, linking it to the unification scale, and discusses experimental prospects for detecting this axion in the predicted mass range.

## Contribution

It presents a model where the axion mass is predicted from grand unification, connecting dark matter properties to fundamental theory.

## Key findings

- Predicted axion mass range: (3 - 13) × 10^{-9} eV.
- ABRACADABRA and CASPEr-Electric experiments can probe this mass window.
- The framework links the Peccei-Quinn scale to the unification scale.

## Abstract

The QCD axion is one of the most appealing candidates for the dark matter in the Universe. In this article, we discuss the possibility to predict the axion mass in the context of a simple renormalizable grand unified theory where the Peccei-Quinn scale is determined by the unification scale. In this framework, the axion mass is predicted to be in the range $m_a \simeq (3 - 13) \times 10^{-9} \ \rm{eV}$. We study the axion phenomenology and find that the ABRACADABRA and CASPEr-Electric experiments will be able to fully probe this mass window.