Precision axion physics with running axion couplings

TL;DR

This paper investigates how axion couplings evolve with energy, considering supersymmetric extensions, and explores whether string-theoretic axions can be distinguished from other models through their low-energy interactions.

Contribution

It provides a detailed analysis of the renormalization group running of axion couplings across different models, highlighting potential experimental signatures for string-theoretic axions.

Findings

String-theoretic axions have similar low-energy couplings to KSVZ-like axions but with distinguishable differences.

The coupling of KSVZ-like QCD axions to electrons is dominated by a three-loop process.

Differences in axion coupling patterns could be tested in future experiments.

Abstract

We study the renormalization group running of axion couplings while taking into account that the Standard Model can be extended to its supersymmetric extension at a certain energy scale below the axion decay constant. We then apply our results to three different classes of axion models, i.e. KSVZ-like, DFSZ-like, and string-theoretic axions, and examine if string-theoretic axions can be distinguished from others by having a different pattern of low energy couplings to the photon, nucleons and electron. We find that the low energy couplings of string-theoretic axions have a similar pattern as those of KSVZ-like axions but yet reveal a sizable difference which might be testable in future axion search experiments. We also note that the coupling of KSVZ-like QCD axions to the electron is dominated by a three-loop contribution involving the exotic heavy quark, gluons, top quark and Higgs field.