scholarly journals Digging into Axion Physics with (Baby)IAXO

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 37
Author(s):  
Theopisti Dafni ◽  
Javier Galán
Keyword(s):  
Decay Constant ◽  
Fourth Generation ◽  
Special Issue ◽  
X Ray ◽  
Axion Mass ◽  
Wide Range ◽  
Discovery Potential ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Main Candidate

Dark matter searches have been ongoing for three decades; the lack of a positive discovery of the main candidate, the WIMP, after dedicated efforts, has put axions and axion-like particles in the spotlight. The three main techniques employed to search for them complement each other well in covering a wide range in the parameter space defined by the axion decay constant and the axion mass. The International AXion Observatory (IAXO) is an international collaboration planning to build the fourth generation axion helioscope, with an unparalleled expected sensitivity and discovery potential. The distinguishing characteristic of IAXO is that it will feature a magnet that is designed to maximise the relevant parameters in sensitivity and which will be equipped with X-ray focusing devices and detectors that have been developed for axion physics. In this paper, we review aspects that motivate IAXO and its prototype, BabyIAXO, in the axion, and ALPs landscape. As part of this Special Issue, some emphasis is given on Spanish participation in the project, of which CAPA (Centro de Astropartículas y Física de Altas Energías of the Universidad de Zaragoza) is a strong promoter.

scholarly journals Maximal axion misalignment from a minimal model

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Junwu Huang ◽  
Amalia Madden ◽  
Davide Racco ◽  
Mario Reig
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Decay Constant ◽  
Axion Mass ◽  
Qcd Phase Transition ◽  
Axion Field ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
The Universe ◽  
Simple Dynamical Model

Abstract The QCD axion is one of the best motivated dark matter candidates. The misalignment mechanism is well known to produce an abundance of the QCD axion consistent with dark matter for an axion decay constant of order 1012 GeV. For a smaller decay constant, the QCD axion, with Peccei-Quinn symmetry broken during inflation, makes up only a fraction of dark matter unless the axion field starts oscillating very close to the top of its potential, in a scenario called “large-misalignment”. In this scenario, QCD axion dark matter with a small axion decay constant is partially comprised of very dense structures. We present a simple dynamical model realising the large-misalignment mechanism. During inflation, the axion classically rolls down its potential approaching its minimum. After inflation, the Universe reheats to a high temperature and a modulus (real scalar field) changes the sign of its minimum dynamically, which changes the sign of the mass of a vector-like fermion charged under QCD. As a result, the minimum of the axion potential during inflation becomes the maximum of the potential after the Universe has cooled through the QCD phase transition and the axion starts oscillating. In this model, we can produce QCD axion dark matter with a decay constant as low as 6 × 109 GeV and an axion mass up to 1 meV. We also summarise the phenomenological implications of this mechanism for dark matter experiments and colliders.

scholarly journals Strong CP problem and axion dark matter with small instantons

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Ryuichiro Kitano ◽  
Wen Yin
Keyword(s):  
Dark Matter ◽  
Decay Constant ◽  
Strongly Coupled ◽  
Axion Mass ◽  
High Energies ◽  
Mass Correction ◽  
Large Correction ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
The Universe

Abstract The axion mass receives a large correction from small instantons if the QCD gets strongly coupled at high energies. We discuss the size of the new CP violating phases caused by the fact that the small instantons are sensitive to the UV physics. We also discuss the effects of the mass correction on the axion abundance of the Universe. Taking the small-instanton contributions into account, we propose a natural scenario of axion dark matter where the axion decay constant is as large as 1015-16 GeV. The scenario works in the high-scale inflation models.

scholarly journals Cosmologically allowed regions for the axion decay constant F

2018 ◽  
Vol 782 ◽  
pp. 181-184 ◽  
Author(s):  
Masahiro Kawasaki ◽  
Eisuke Sonomoto ◽  
Tsutomu T. Yanagida
Keyword(s):  
Decay Constant ◽  
Axion Decay Constant ◽  
Axion Decay

scholarly journals Numerical analysis of Coleman–de Luccia tunneling

2016 ◽  
Vol 31 (24) ◽  
pp. 1650131 ◽  
Author(s):  
Yuhei Goto ◽  
Kazumi Okuyama
Keyword(s):  
Decay Constant ◽  
Periodic Potential ◽  
Thin Wall ◽  
False Vacuum ◽  
Vacuum Decay ◽  
Text Type ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Range Of Values ◽  
Type Potential

In this paper, we study the false vacuum decay of a single scalar field [Formula: see text] coupled to gravity described by the Coleman–de Luccia (CdL) instanton. We show that it is possible to numerically calculate the bounce factor, which is related to the CdL tunneling rate, without using the thin-wall approximation. In this paper, we consider [Formula: see text]- and [Formula: see text]-type potentials as examples, which have cosmological and phenomenological applications. Especially, in the [Formula: see text]-type potential, we show that the range of values in which axion decay constant can take is restricted by the form of the periodic potential if the CdL tunneling occurs.

ON THE SUPERSTRING AXION MINI-STAR

1998 ◽  
Vol 13 (13) ◽  
pp. 1007-1017 ◽  
Author(s):  
M. D. POLLOCK
Keyword(s):  
Gravitational Collapse ◽  
Mass Formula ◽  
Decay Constant ◽  
Gravitational Constant ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Planck Mass ◽  
Upper Limit ◽  
Axion Decay Constant ◽  
Axion Decay

The theory of the pressure-free-boson mini-star of mass M, whose radius r=2GM/v2 is equated via the indeterminacy principle to ℏ/mv, where [Formula: see text] is the Newton gravitational constant, M P being the Planck mass and m the mass of the boson, travelling at velocity v, is applied to the superstring axion. For a bounded object, the upper limit to the axion potential [Formula: see text] constrains the axions to move at non-relativistic velocities [Formula: see text] where [Formula: see text] GeV is the axion decay constant, predicting the existence of an axion mini-star of mass [Formula: see text]. Such objects can in principle form by gravitational collapse below the temperature T≈100 eV, and are tentatively identified with the microlensing objects recently detected in our Galaxy and in the direction of the Large Magellanic Cloud.

scholarly journals Challenges for an axion explanation of the muon g − 2 measurement

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Manuel A. Buen-Abad ◽  
JiJi Fan ◽  
Matthew Reece ◽  
Chen Sun
Keyword(s):  
Decay Constant ◽  
Standard Model Prediction ◽  
New Physics ◽  
Effective Theory ◽  
General Sense ◽  
Weak Scale ◽  
Initial Application ◽  
The Standard Model ◽  
Axion Decay Constant ◽  
Axion Decay

Abstract The discrepancy between the muon g − 2 measurement and the Standard Model prediction points to new physics around or below the weak scale. It is tantalizing to consider the loop effects of a heavy axion (in the general sense, also known as an axion-like particle) coupling to leptons and photons as an explanation for this discrepancy. We provide an updated analysis of the necessary couplings, including two-loop contributions, and find that the new physics operators point to an axion decay constant on the order of 10s of GeV. This poses major problems for such an explanation, as the axion couplings to leptons and photons must be generated at low scales. We outline some possibilities for how such couplings can arise, and find that these scenarios predict new charged matter at or below the weak scale and new scalars can mix with the Higgs boson, raising numerous phenomenological challenges. These scenarios also all predict additional contributions to the muon g−2 itself, calling the initial application of the axion effective theory into question. We conclude that there is little reason to favor an axion explanation of the muon g – 2 measurement relative to other models postulating new weak-scale matter.

Axions from heterotic stringThis paper was presented at the Theory CANADA 4 conference, held at Centre de recherches mathématiques, Montréal, Québec, Canada on 4–7 June 2008.

2009 ◽  
Vol 87 (3) ◽  
pp. 267-270
Author(s):  
Keshav Dasgupta ◽  
Hassan Firouzjahi ◽  
Rhiannon Gwyn
Keyword(s):  
String Theory ◽  
Decay Constant ◽  
Mass Scale ◽  
Heterotic String ◽  
Explicit Model ◽  
Heterotic String Theory ◽  
Natural Mechanism ◽  
Axion Decay Constant ◽  
Axion Decay

We study the axion in a warped heterotic background. It is shown that the axion decay constant, fa, is sensitive to the warped mass scale of the throat. As an explicit model, we construct a novel AdS-like geometry in heterotic string theory. We demonstrate that in this background fa is given by the mass scale of the longest throat in the compactification. The question of obtaining fa within the required bound 109–1012 GeV is reduced to the construction of a throat inside the heterotic string theory compactification with warped mass scale in the above range. This provides a natural mechanism for realising the axion in heterotic string theory.

scholarly journals The stochastic axiverse

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Mario Reig
Keyword(s):  
Black Hole ◽  
Dark Energy ◽  
Decay Constant ◽  
Planck Scale ◽  
Potential Minimum ◽  
Long Period ◽  
Cmb Polarization ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Fundamental Requirement

Abstract In addition to spectacular signatures such as black hole superradiance and the rotation of CMB polarization, the plenitude of axions appearing in the string axiverse may have potentially dangerous implications. An example is the cosmological overproduction of relic axions and moduli by the misalignment mechanism, more pronounced in regions where the signals mentioned above may be observable, that is for large axion decay constant. In this work, we study the minimal requirements to soften this problem and show that the fundamental requirement is a long period of low-scale inflation. However, in this case, if the inflationary Hubble scale is lower than around O(100) eV, no relic DM axion is produced in the early Universe. Cosmological production of some axions may be activated, via the misalignment mechanism, if their potential minimum changes between inflation and today. As a particular example, we study in detail how the maximal-misalignment mechanism dilutes the effect of dangerous axions and allows the production of axion DM in a controlled way. In this case, the potential of the axion that realises the mechanism shifts by a factor ∆θ = π between the inflationary epoch and today, and the axion starts to oscillate from the top of its potential. We also show that axions with masses ma ∼ O(1 − 100) H0 realising the maximal-misalignment mechanism generically behave as dark energy with a decay constant that can take values well below the Planck scale, avoiding problems associated to super-Planckian scales. Finally, we briefly study the basic phenomenological implications of the mechanism and comment on the compatibility of this type of maximally-misaligned quintessence with the swampland criteria.

scholarly journals Axions and anomalous U(1)’s

2018 ◽  
Vol 33 (34) ◽  
pp. 1845001 ◽  
Author(s):  
Quentin Bonnefoy ◽  
Emilian Dudas
Keyword(s):  
Decay Constant ◽  
Vacuum Expectation ◽  
Expectation Values ◽  
Charged Scalar ◽  
Gauge Groups ◽  
Axion Mass ◽  
Decay Constants ◽  
Nonperturbative Effect ◽  
String Models ◽  
Axion Decay

Inspired by recent studies of high-scale decay constant or flavorful QCD axions, we review and clarify their existence in effective string models with anomalous U(1) gauge groups. We find that such models, when coupled to charged scalars getting vacuum expectation values, always have one light axion, whose mass can only come from nonperturbative effects. If the main nonperturbative effect is from QCD, then it becomes a Peccei–Quinn axion candidate for solving the strong CP problem. We then study simple models with universal Green–Schwarz mechanism and only one charged scalar field: in the minimal gaugino condensation case the axion mass is tied to the supersymmetry breaking scale and cannot be light enough, but slightly refined models maintain a massless axion all the way down to the QCD scale. Both kinds of models can be extended to yield intermediate scale axion decay constants. Finally, we gauge flavorful axion models under an anomalous U(1) and discuss the axion couplings which arise.

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