Naturally astrophobic QCD axion

TL;DR

This paper proposes a QCD axion model with naturally suppressed couplings to Standard Model particles, allowing for a smaller decay constant and potential direct detection, while addressing flavor violation and stellar cooling hints.

Contribution

It introduces a novel axion model with specific Peccei-Quinn charge assignments that suppress couplings and explores the phenomenological implications including detection prospects.

Findings

Axion decay constant can be as low as 10^7 GeV.

Axion mass can be above 1 eV, enabling direct detection.

Flavor-violating couplings can be naturally suppressed.

Abstract

We present a QCD axion model where the couplings of the axion to nucleons, electrons, and muons are naturally suppressed because of the appropriate choice of the Peccei-Quinn charges of the Standard Model fermions. We reexamine next-to-leading order corrections to the couplings of the axion with nucleons and photons and show that the axion decay constant may be as small as $10^7$ GeV. It is also possible to suppress the coupling with the photon so that the decay constant is even smaller and minimal axiogenesis works. In this scenario, the axion has a mass above 1 eV and may be directly detected via absorption of axion dark matter. Flavor-violating axion couplings are generically predicted in our model, but we show that they may be naturally and sufficiently suppressed. We discuss the implications of the hints for anomalous cooling in several stellar environments to our model.