New experimental approaches in the search for axion-like particles

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 a 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 interest in axion searches. The experimental landscape is rapidly evolving, with many novel detection concepts and new experimental proposals. An updated account of those initiatives is lacking in the literature. In this review we attempt to provide such an update. 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.

Experimental implementations of cavity-magnon systems: from ultra strong coupling to applications in precision measurement

“…Large cavity-magnon couplings lead to a larger range of frequencies and hence axion masses that the experiment can be sensitive to [11]. Thus the USC achieved here would be advantageous for such an experiment to explore a larger range of the, as yet, unknown axion mass parameter space [56].…”

Axion dark matter from Higgs inflation with an intermediate H*

“…In Fig. 2, we also show the expected reach of the haloscope searches [35,[159][160][161] by ADMX [162][163][164][165] and KLASH [166], which are also going to explore values of the axion mass that are lighter than what has been recently inferred by numerical computations of the dynamics of the PQ field [16][17][18][19]36] in a different cosmological scenario. On a theoretical viewpoint, the results obtained do not depend on the coupling of the QCD axion with the photons [167][168][169][170], which is nonetheless present when considering the experimental setup [171][172][173][174][175][176].…”

“…Light QCD axions that spectate inflation have recently received attention both from the theory perspective [23-27, 29, 30, 34] and from the perspective of detection in proposed and ongoing experiments [35]. In such a scenario, topological defects are washed out by inflation, and considerable additional effort to assess inhomogeneities like axion strings [16,36,37] or axion miniclusters [38][39][40][41][42] is not required.…”

GAMBIT and its application in the search for physics Beyond the Standard Model

“…T χ and β are in principle calculable, but can be left as nuisance parameters in order to account for systematic uncertainties in the calculations. In fact, QCD axions are only one instance of a general class of axion-like particles (ALPs), which could generally result from the breaking of a U (1) symmetry at some scale f a , with mass generation occurring via the explicit breaking of the residual symmetry at some lower scale Λ [354][355][356]. It can be shown that in a Friedmann-Robertson-Walker-Lemaître universe, a QCD axion or ALP field θ(t) = a(t)/f a satisfies the equation of motion…”