# Axions are blind to anomalies

## TL;DR

This paper demonstrates that axion couplings to gauge bosons originate from non-anomalous fermion loops, challenging the traditional anomaly-based understanding, especially impacting chiral gauge theories and axion-like particle searches.

## Contribution

It proves that axion couplings are independent of anomaly structures and provides explicit calculations showing deviations from expected anomaly patterns in chiral gauge theories.

## Key findings

- Axion couplings arise from non-anomalous fermion loops.
- Couplings to electroweak gauge bosons do not follow anomaly patterns.
- Implications for axion-like particle searches are significant.

## Abstract

The axion couplings to SM gauge bosons are derived in various models, and shown to always arise entirely from non-anomalous fermion loops. They are thus independent of the anomaly structure of the model. This fact is without consequence for vector gauge interactions like QCD and QED, but has a major impact for chiral gauge theories. For example, in the DFSZ axion model, the couplings of axions to electroweak gauge bosons do not follow the pattern expected from chiral anomalies, as we prove by an explicit calculation. The reason for this mismatch is traced back to triangle Feynman diagrams sensitive to the anomalous breaking of the vector Ward identity, and is ultimately related to the conservation of baryon and lepton numbers. Though our analyses are entirely done for true axion models, this observation could have important consequences for axion-like particle searches.