New experimental approaches in the search for axion-like particles

TL;DR

This paper reviews recent experimental approaches to detect axion-like particles, highlighting new detection concepts, recent results, and future prospects in the context of their theoretical and cosmological significance.

Contribution

It provides a comprehensive overview of novel experimental methods and their complementarity in the search for axion-like particles, updating the field's landscape.

Findings

Summary of recent experimental results

Discussion of new detection concepts

Prospects for future experiments

Abstract

Axions and other very light axion-like particles appear in many extensions of the Standard Model, and are leading candidates to compose part or all of the missing matter of the Universe. They also appear in models of inflation, dark radiation, or even dark energy, and could solve some long-standing astrophysical anomalies. The physics case of these particles has been considerably developed in recent years, and there are now useful guidelines and powerful motivations to attempt experimental detection. Admittedly, the lack of positive signal of new physics at the high energy frontier, and in underground detectors searching for weakly interacting massive particles, is also contributing to the increase of the interest in axion searches. The experimental landscape is rapidly evolving, with many novel detection concepts and new experiments being proposed lately. An updated account of those initiatives is lacking in the literature. In this review we attempt to provide such a review. We will focus on the new experimental approaches and their complementarity, but will also review the most relevant recent results from the consolidated strategies and the prospects of new generation experiments under consideration in the field. We will also briefly review the latest developments of the theory, cosmology and astrophysics of axions and we will discuss the prospects to probe a large fraction of relevant parameter space in the coming decade.