scholarly journals Axion–Sterile Neutrino Dark Matter

Universe ◽  
2021 ◽  
Vol 7 (10) ◽  
pp. 354
Author(s):  
Alberto Salvio ◽  
Simone Scollo
Keyword(s):  
Dark Matter ◽  
Decay Constant ◽  
Sterile Neutrino ◽  
Topological Defects ◽  
Primordial Black Holes ◽  
Neutrino Production ◽  
The Standard Model ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Production Mechanisms

Extending the standard model with three right-handed neutrinos and a simple QCD axion sector can account for neutrino oscillations, dark matter and baryon asymmetry; at the same time, it solves the strong CP problem, stabilizes the electroweak vacuum and can implement critical Higgs inflation (satisfying all current observational bounds). We perform here a general analysis of dark matter (DM) in such a model, which we call the aνMSM. Although critical Higgs inflation features a (quasi) inflection point of the inflaton potential, we show that DM cannot receive a contribution from primordial black holes in the aνMSM. This leads to a multicomponent axion–sterile neutrino DM and allows us to relate the axion parameters, such as the axion decay constant, to the neutrino parameters. We include several DM production mechanisms: the axion production via misalignment and decay of topological defects as well as the sterile neutrino production through the resonant and non-resonant mechanisms and in the recently proposed CPT-symmetric universe.

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.

scholarly journals Precision axion physics with running axion couplings

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Kiwoon Choi ◽  
Sang Hui Im ◽  
Hee Jung Kim ◽  
Hyeonseok Seong
Keyword(s):  
Top Quark ◽  
Decay Constant ◽  
Higgs Field ◽  
Energy Scale ◽  
Low Energy ◽  
Loop Contribution ◽  
The Standard Model ◽  
Axion Decay Constant ◽  
Axion Decay ◽  
Sizable Difference

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.

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 Sterile Neutrinos as Dark Matter: Alternative Production Mechanisms in the Early Universe

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 264
Author(s):  
Daniel Boyanovsky
Keyword(s):  
Dark Matter ◽  
Distribution Function ◽  
Kinetic Equation ◽  
Standard Model ◽  
Early Universe ◽  
Quantum Kinetic Equation ◽  
Sterile Neutrinos ◽  
The Standard Model ◽  
Production Mechanisms ◽  
Freeze Out

We study various production mechanisms of sterile neutrinos in the early universe beyond and within the standard model. We obtain the quantum kinetic equations for production and the distribution function of sterile-like neutrinos at freeze-out, from which we obtain free streaming lengths, equations of state and coarse grained phase space densities. In a simple extension beyond the standard model, in which neutrinos are Yukawa coupled to a Higgs-like scalar, we derive and solve the quantum kinetic equation for sterile production and analyze the freeze-out conditions and clustering properties of this dark matter constituent. We argue that in the mass basis, standard model processes that produce active neutrinos also yield sterile-like neutrinos, leading to various possible production channels. Hence, the final distribution function of sterile-like neutrinos is a result of the various kinematically allowed production processes in the early universe. As an explicit example, we consider production of light sterile neutrinos from pion decay after the QCD phase transition, obtaining the quantum kinetic equation and the distribution function at freeze-out. A sterile-like neutrino with a mass in the keV range produced by this process is a suitable warm dark matter candidate with a free-streaming length of the order of few kpc consistent with cores in dwarf galaxies.

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 Signals of Dark Matter in hypercolor vectorlike extension of the SM

2019 ◽  
Vol 222 ◽  
pp. 04002
Author(s):  
Vitaly Beylin ◽  
Maxim Bezuglov ◽  
Egor Tretiakov
Keyword(s):  
Dark Matter ◽  
Cosmic Rays ◽  
Standard Model ◽  
Neutrino Detectors ◽  
Neutrino Production ◽  
The Standard Model ◽  
Different Origin

In the framework of hypercolor extension of the Standard Model we consider cosmic rays scattering off hidden mass candidates. Specifically, there are two components of the Dark Matter in this model having close masses but different origin. As a result, neutrino production in the processes of scattering ofhigh energy electrons on these DM candidates is substantially different, and the secondary neutrino canbe seen, in principle, at neutrino detectors. We also note other interesting aspects of these type reactions.

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.

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