Hadrophobic Axion from GUT

TL;DR

This paper introduces a GUT-based axion model that is hadrophobic and electrophobic, offering a unified explanation for the strong CP problem, dark matter, and inflation, with distinctive experimental signatures.

Contribution

It proposes a novel GUT-derived axion model with specific charge assignments that naturally suppress hadronic and electronic couplings, linking flavor physics, dark matter, and stellar cooling.

Findings

The axion can serve as the QCD axion solving the strong CP problem.

The model predicts axion couplings consistent with stellar cooling constraints.

Viable parameter space links axion properties to GUT and flavor physics.

Abstract

We propose a new kind of axion model derived from the Grand Unified Theory (GUT) based on $SU(5)\times U(1)_{\rm PQ}$. We demonstrate that, given a certain charge assignment and potential flavor models, the axion is naturally hadrophobic and provides a novel explanation for the required condition using isospin symmetry. This axion can be the QCD axion that solves the strong CP problem. Furthermore, to satisfy the limit on the axion-electron coupling from the tip of the red giant branch, we impose the condition of electrophobia to determine a possible PQ charge assignment consistent with GUT. We then discuss the possibility that the hadrophobic and electrophobic axion serves as an inflaton and dark matter, as in the ALP miracle scenario. Interestingly, in the viable parameter region, the strong CP phase must be suppressed, providing another solution to the strong CP problem. This scenario is intimately linked to flavor physics, dark matter searches, and stellar cooling. Detecting such an axion with peculiar couplings in various experiments would serve as a probe for GUT and the origin of flavor.