Axion Bounds from Quantum Technology

TL;DR

This paper develops a comprehensive quantum field theory framework for axion-like particles (ALPs), analyzing their interactions, renormalization effects, and experimental detection strategies, especially focusing on quantum sensors and dark matter implications.

Contribution

It introduces a detailed treatment of ALP interactions including running effects, relates linear and quadratic couplings, and proposes novel experimental search strategies.

Findings

Quantifies the sensitivity of current and future experiments to ALPs.

Establishes the relationship between linear and quadratic ALP interactions.

Identifies experimental regimes where ALP signals are background-independent.

Abstract

A consistent treatment of the quantum field theory of an axion-like particle (ALP) interacting with Standard Model fields requires to account for renormalisation group running and matching to the low-energy theory. Quantum sensor experiments designed to search for very light ALPs are particularly sensitive to these effects because they probe large values of the decay constant for which running effects become important. In addition, while linear axion interactions are set by its pseudoscalar nature, quadratic interactions are indistinguishable from scalar interactions. We show how the Wilson coefficients of linear and quadratic ALP interactions are related, including running effects above and below the QCD scale and provide a comprehensive analysis of the sensitivity of current and future experiments. We identify the reach of different experiments for the case of ALP dark matter and comment on how it could be distinguished from the case where it is not the dark matter. We present novel search strategies to observe quadratic ALP interactions via fifth force searches, haloscopes, helioscopes and quantum sensors. We emphasize the nonlinear behaviour of the ALP field close to the surface of the earth and point out which experimental results are independent on the local background field value.