Future cosmological sensitivity for hot dark matter axions

ArXiv, 2024

Based upon a previous axion mass proposal and detection scheme, as well as considering the axion mass ranges suggested by cogent simulations in recent years, we present a revised axion/ALP search strategy and our calculations, concentrating on a narrow axion mass (and corresponding Compton frequency) window in this report. The window comprises the spectral region of 18.99 to 19.01GHz (that falls within the Ku microwave band), with a center frequency of 19.00GHz (+0.1GHz), with equivalence to am axion mass range of 78.6 to 79.6 eV, with the center mass at the value of 78.582 (+5.0) eV, our suggested most likely value for an axionic/ALP field mass, if these fields exist. Our search strategy, as summarized herewith, is based upon the assumption that the dark matter that exists in the current epoch of our physical universe is dominated by axions and thus the local observable axion density is the density of the light cold dark matter, permeating our local neighborhood (mainly in the Milky Way galactic halo). Some ideas and the design of an experiment, built around a Josephson Parametric Amplifier and Resonant Tunneling Diode combo installed in a resonant RF cavity, are also introduced in this report.

Physical Review D, 2007

Relic thermal axions could play the role of an extra hot dark matter component in cosmological structure formation theories. By combining the most recent observational data we improve previous cosmological bounds on the axion mass ma in the so-called hadronic axion window. We obtain a limit on the axion mass ma < 0.42 eV at the 95% c.l. (ma < 0.72 eV at the 99% c.l.). A novel aspect of the analysis presented here is the inclusion of massive neutrinos and how they may affect the bound on the axion mass. If neutrino masses belong to an inverted hierarchy scheme, for example, the above constraint is improved to ma < 0.38 eV at the 95% c.l. (ma < 0.67 eV at the 99% c.l.). Future data from experiments as CAST will provide a direct test of the cosmological bound.

Proceedings of 40th International Conference on High Energy physics — PoS(ICHEP2020), 2021

The axion is a hypothetical particle associated with the spontaneous symmetry breaking of the (1) symmetry, proposed by Pecci and Quinn to resolve the Charge-Parity () problem in quantum chromodynamics. For invisible axions, cosmological and astrophysical observations impose the lower and upper limits on axion mass of eV and meV respectively. The axion in such a mass range could be a promising candidate for the cold dark matter. The CAPP-8TB experiment searches for the axion by detecting photons, produced by the axion-photon coupling, resonating in a microwave cavity. The experiment has recently obtained a result of axion search in the mass range of 6.62-6.82 eV. At the 90 % confidence level we probed the QCD axion down to a theoretical boundary, which is the most sensitive experimental result in the specific mass range to date. In this paper we will explain the detail of the experimental setup, parameters and analysis procedure. A plan for the next phase of the experiment for different mass ranges will also be discussed.

2008

We derive cosmological limits on two-component hot dark matter consisting of neutrinos and axions. We restrict the large-scale structure data to the safely linear regime, excluding the Lyman-alpha forest. We derive Bayesian credible regions in the two-parameter space consisting of m_a and sum(m_nu). Marginalizing over sum(m_nu) provides m_a&lt;1.02 eV (95% CL). In the absence of axions the same data and

Axions are well-motivated dark matter candidates with simple cosmological production mechanisms. They were originally introduced to solve the strong CP problem, but also arise in a wide range of extensions to the Standard Model. This Snowmass white paper summarizes axion phenomenology and outlines next-generation laboratory experiments proposed to detect axion dark matter. There are vibrant synergies with astrophysical searches and advances in instrumentation including quantumenabled readout, high-Q resonators and cavities and large high-field magnets. This white paper outlines a clear roadmap to discovery, and shows that the US is wellpositioned to be at the forefront of the search for axion dark matter in the coming decade.

Journal of Cosmology and Astroparticle Physics, 2007

We use observations of the cosmological large-scale structure to derive limits on two-component hot dark matter consisting of mass-degenerate neutrinos and hadronic axions, both components having velocity dispersions corresponding to their respective decoupling temperatures. We restrict the data samples to the safely linear regime, in particular excluding the Lyman-α forest. Using standard Bayesian inference techniques we derive credible regions in the two-parameter space of m a and m ν . Marginalizing over m ν provides m a < 1.2 eV (95% C.L.). In the absence of axions the same data and methods give m ν < 0.65 eV (95% C.L.). We also derive limits on m a for a range of axion-pion couplings up to one order of magnitude larger or smaller than the hadronic value.

Journal of Cosmology and Astroparticle Physics, 2011

Axions with mass m a > ∼ 0.7 eV are excluded by cosmological precision data because they provide too much hot dark matter. While for m a > ∼ 20 eV the a → 2γ lifetime drops below the age of the universe, we show that the cosmological exclusion range can be extended to 0.7 eV < ∼ m a < ∼ 300 keV, primarily by the cosmic deuterium abundance: axion decays would strongly modify the baryon-to-photon ratio at BBN relative to the one at CMB decoupling. Additional arguments include neutrino dilution relative to photons by axion decays and spectral CMB distortions. Our new cosmological constraints complement stellar-evolution and laboratory bounds.

Proceedings of European Physical Society Conference on High Energy Physics — PoS(EPS-HEP2019), 2020

The axion is a hypothetical particle proposed to solve the strong CP problem, and also a candidate for dark matter. This non-relativistic particle in the galactic halo can be converted into a photon under a strong magnetic field and detected with a microwave resonant cavity. Relying on this detection method, many experiments have excluded some mass regions with certain sensitivities in terms of axion-photon coupling (g aγγ) for decades, but no axion dark matter has been discovered to date. CAPP-8TB is another axion haloscope experiment at IBS/CAPP designed to search for the axion in a mass range of 6.62 to 7.04 µeV. The experiment aims for the most sensitive axion dark matter search in this particular mass range with its first-phase sensitivity reaching the QCD axion band. In this presentation, we discuss the overview of the experiment, and present the first result. We also discuss an upgrade of the experiment to achieve higher sensitivity.

Physical Review Letters, 2014

The CERN Axion Solar Telescope (CAST) has finished its search for solar axions with 3 He buffer gas, covering the search range 0.64 eV < ∼ ma < ∼ 1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess X-rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gaγ < ∼ 3.3 × 10 −10 GeV −1 at 95% CL, with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of gaγ, for example by the currently discussed next generation helioscope IAXO. PACS numbers: 95.35.+d, 14.80.Mz, 07.85.Nc, 84.71.Ba

Journal of Cosmology and Astroparticle Physics

We review the physics potential of a next generation search for solar axions: the International Axion Observatory (IAXO). Endowed with a sensitivity to discover axion-like particles (ALPs) with a coupling to photons as small as g aγ ∼ 10 −12 GeV −1 , or to electrons g ae ∼10 −13 , IAXO has the potential to find the QCD axion in the 1 meV∼1 eV mass range where it solves the strong CP problem, can account for the cold dark matter of the Universe and be responsible for the anomalous cooling observed in a number of stellar systems. At the same time, IAXO will have enough sensitivity to detect lower mass axions invoked to explain: 1) the origin of the anomalous "transparency" of the Universe to gamma-rays, 2) the observed soft X-ray excess from galaxy clusters or 3) some inflationary models. In addition, we review string theory axions with parameters accessible by IAXO and discuss their potential role in cosmology as Dark Matter and Dark Radiation as well as their connections to the above mentioned conundrums.