Axion-like Particles Research Articles

Anisotropies in cosmological 21 cm background by oscillons/I-balls of ultra-light axion-like particle

Ultra-light axion-like particle (ULAP) with mass m ∼ 10-22 eV has recently been attracting attention as a possible solution to the small-scale crisis. ULAP forms quasi-stable objects called oscillons/I-balls, which can survive up to a redshift z ∼ 10 and affect the structure formation on a scale ∼ \U0001d4aa(0.1) Mpc by amplifying the density fluctuations. We study the effect of oscillons on 21 cm anisotropies caused by neutral hydrogen in minihalos. It is found that this effect can be observed in a wide mass range by future observations such as Square Kilometer Array (SKA) if the fraction of ULAP to the total dark matter density is \U0001d4aa(0.01 – 0.1).

Limits on Axions and Axionlike Particles within the Axion Window Using a Spin-Based Amplifier.

Searches for the axion and axionlike particles may hold the key to unlocking some of the deepest puzzles about our Universe, such as dark matter and dark energy. Here, we use the recently demonstrated spin-based amplifier to constrain such hypothetical particles within the well-motivated "axion window" (10 μeV-1 meV) through searching for an exotic dipole-dipole interaction between polarized electron and neutron spins. The key ingredient is the use of hyperpolarized long-lived ^{129}Xe nuclear spins as an amplifier for the pseudomagnetic field generated by the exotic interaction. Using such a spin sensor, we obtain a direct upper bound on the product of coupling constants g_{p}^{e}g_{p}^{n}. The spin-based amplifier technique can be extended to searches for a wide variety of hypothetical particles beyond the standard model.

Fuzzy dark matter and the Dark Energy Survey Year 1 data

ABSTRACT Gravitational weak lensing by dark matter haloes leads to a measurable imprint in the shear correlation function of galaxies. Fuzzy dark matter (FDM), composed of ultralight axion-like particles of mass m ∼ 10−22 eV, suppresses the matter power spectrum and shear correlation with respect to standard cold dark matter. We model the effect of FDM on cosmic shear using the optimized halo model HMCode, accounting for additional suppression of the mass function and halo concentration in FDM as observed in N-body simulations. We combine Dark Energy Survey Year 1 (DES-Y1) data with the Planck cosmic microwave background anisotropies to search for shear correlation suppression caused by FDM. We find no evidence of suppression compared to the preferred cold dark matter model, and thus set a new lower limit to the FDM particle mass. Using a log-flat prior and marginalizing over uncertainties related to the non-linear model of FDM, we find a new, independent 95 per cent C.L. lower limit log10m > −23 combining Planck and DES-Y1 shear, an improvement of almost two orders of magnitude on the mass bound relative to CMB-only constraints. Our analysis is largely independent of baryonic modelling, and of previous limits to FDM covering this mass range. Our analysis highlights the most important aspects of the FDM non-linear model for future investigation. The limit to FDM from weak lensing could be improved by up to three orders of magnitude with $\mathcal {O}(0.1)$ arcmin cosmic shear angular resolution, if FDM and baryonic feedback can be simultaneously modelled to high precision in the halo model.

Anomalous coupling studies with forward protons at the LHC

We describe the gain on sensitivities to quartic \gamma \gamma \gamma \gammaγγγγ, \gamma \gamma WWγγWW and \gamma \gamma \gamma ZγγγZ anomalous couplings and to the search for Axion-Like Particles by two or three orders of magnitude with respect to standard methods at the LHC by tagging intact protons in the final state.

Direct search for dark matter axions excluding ALP cogenesis in the 63- to 67-μeV range with the ORGAN experiment.

The standard model axion seesaw Higgs portal inflation (SMASH) model is a well-motivated, self-contained description of particle physics that predicts axion dark matter particles to exist within the mass range of 50 to 200 micro–electron volts. Scanning these masses requires an axion haloscope to operate under a constant magnetic field between 12 and 48 gigahertz. The ORGAN (Oscillating Resonant Group AxioN) experiment (in Perth, Australia) is a microwave cavity axion haloscope that aims to search the majority of the mass range predicted by the SMASH model. Our initial phase 1a scan sets an upper limit on the coupling of axions to two photons of ∣gaγγ∣ ≤ 3 × 10−12 per giga–electron volts over the mass range of 63.2 to 67.1 micro–electron volts with 95% confidence interval. This highly sensitive result is sufficient to exclude the well-motivated axion-like particle cogenesis model for dark matter in the searched region.

Search for dark matter with an LC circuit

The focus on the dark matter search has expanded to include low-mass particles such as axions or axionlike particles, and novel theoretical schemes extending the phenomenological landscape, within QCD and beyond, also garnered additional interest in recent decades. Assuming dark matter is composed of axions, in the presence of a solenoidal magnetic field, they induce a displacement current that gives rise to a toroidal magnetic field. The weakly interacting slender particle detection with an $LC$ circuit (WISPLC) is a precision direct detection experiment that will search for light dark matter candidates such as axionlike particles in parts of the parameter space previously unexplored. We present two detection schemes of the signal in a pickup loop capturing the flux of this toroidal magnetic field. WISPLC operates in a broadband and a resonant scheme where an $LC$ circuit is used to enhance the signal with an expected $Q$ factor $\ensuremath{\sim}{10}^{4}$. Taking into account the irreducible flux noise of the detector, we estimate the sensitivity of the experiment in the axion mass range between ${10}^{\ensuremath{-}11}$ and ${10}^{\ensuremath{-}6}\text{ }\text{ }\mathrm{eV}$ to reach a detectable axion-photon coupling of ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}\ensuremath{\approx}{10}^{\ensuremath{-}15}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$, making it possible to probe mass ranges corresponding to ultralight axions motivated by string theory. The WISPLC experiment is fully funded and currently in the construction phase.

Static axionlike dark matter clouds around magnetized rotating wormholes–probe limit case

The problem of the distribution of axionlike particle, being the model of dark matter, in the nearby of rotating wormholes has been investigated numerically. In the model in question the axion scalar is non-trivially coupled to the Maxwell gauge field. We consider two toy models of rotating wormholes embedded in magnetic field, Kerr-like and Teo rotating wormholes. Moreover one assumes that the matter fields will not backreact on the wormhole spacetimes, i.e., we shall study the problem in the probe limit case. We point out the differences in the distribution of dark matter comparing to the location of it in the vicinity of rotating magnetized black holes.

The ALPs from the top: searching for long lived axion-like particles from exotic top decays

We propose a search for long lived axion-like particles (ALPs) in exotic top decays. Flavour-violating ALPs appear as low energy effective theories for various new physics scenarios such as t-channel dark sectors or Froggatt-Nielsen models. In this case the top quark may decay to an ALP and an up- or charm-quark. For masses in the few GeV range, the ALP is long lived across most of the viable parameter space, suggesting a dedicated search. We propose to search for these long lived ALPs in toverline{t} events, using one top quark as a trigger. We focus on ALPs decaying in the hadronic calorimeter, and show that the ratio of energy deposits in the electromagnetic and hadronic calorimeters as well as track vetoes can efficiently suppress Standard Model backgrounds. Our proposed search can probe exotic top branching ratios smaller than 10−4 with a conservative strategy at the upcoming LHC run, and potentially below the 10−7 level with more advanced methods. Finally we also show that measurements of single top production probe these branching ratios in the very short and very long lifetime limit at the 10−3 level.

ALPINIST: Axion-Like Particles In Numerous Interactions Simulated and Tabulated

Proton beam dump experiments are among the most promising strategies to search for light and feebly interacting states such as axion-like particles (ALPs). The interpretation of these experiments is however complicated by the wide range of ALP models and the multitude of different production and decay channels that can induce observable signals. Here we propose a new approach to this problem by separating the calculation of constraints and projected sensitivities into model-independent and model-dependent parts. The former rely on extensive Monte Carlo simulations of ALP production and decays, as well as estimates of the detection efficiencies based on simplified detector geometries. Once these simulations have been performed and tabulated, the latter parts only require simple analytical rescalings that can be performed using the public code ALPINIST released together with this work. We illustrate this approach by considering several ALP models with couplings to Standard Model gauge bosons. For the case of ALPs coupled to gluons we show that the sensitivity of proton beam dump experiments can be extended significantly by considering hadronic ALP decays into three-body final states.

Cosmological relaxation through the dark axion portal

The dark axion portal is a coupling of an axion-like particle to a dark photon kinetically mixed with the visible photon. We show how this portal, when applied to the relaxion, can lead to cosmological relaxation of the weak scale using dark photon production. The key backreaction mechanism involves the Schwinger effect: as long as electroweak symmetry is unbroken, Schwinger production of massless Standard Model fermions, which carry dark millicharges, suppresses the dark photon production. Once the electroweak symmetry is broken, the fermions acquire mass and the suppression is lifted. An enhanced dark photon dissipation then traps the relaxion at a naturally small weak scale. Our model thus provides a novel link between the phenomenological dark axion portal, dark photons, and the hierarchy problem of the Higgs mass.

Constraining Heavy Axionlike Particles by Energy Deposition in Globular Cluster Stars.

Heavy axionlike particles (ALPs) with masses up to a few 100keV and coupled with photons can be efficiently produced in stellar plasmas. We present a new "ballistic" recipe that covers both the energy-loss and energy-transfer regimes, and we perform the first dedicated simulation of Globular Cluster stars including the ALP energy transfer. This argument allows us to constrain ALPs with m_{a}≲0.4 MeV and g_{aγ}≃10^{-5} GeV^{-1}, probing a section of the ALP parameter space informally known as the "cosmological triangle". This region is particularly interesting since it has been excluded only using standard cosmological arguments that can be evaded in nonstandard scenarios.

Flavor physics with generalized ALP-quark couplings

A light axionlike particle or an axionlike particle (ALP) not just gives rise to interesting and spectacular signals of new physics as final states in meson decays, it necessarily leaves tell-tale signatures in processes that involve standard model (SM) fields only (i.e., SM processes). These effects result in the violation of the Gell-Mann-Okubo mass relation, modified form factors, altered integrated and differential rates for various SM transitions etc. This suggests that in the presence of a low lying state, such as an ALP, extraction of masses, mixing angles, and form factors in an entirely data-driven way from meson-physics observables is a highly nontrivial exercise. However, once done correctly, these same observables may, in turn, provide important (indirect) bounds on ALP physics, which remain robust even in the limits where new physics effects conspire to weaken the bounds from direct searches. Starting with a generalized ALP-quark Lagrangian (where restrictions due to parity are removed) we demonstrate this approach by focusing on ${K}_{{\ensuremath{\ell}}_{3}}^{+}$ decays, where we derive (indirect) bounds on ALP physics using $\mathrm{NA}48/2$ data and lattice results. We also find sum rules that not just show deviations in the presence of an ALP but also give hints towards the specific nature of the ALP physics itself.

TAIGA—A hybrid array for high energy gamma-ray astronomy and cosmic-ray physics

The concept of the TAIGA experiment is to combine wide-angle timing and imaging Cherenkov telescopes as well as electron and muon detectors. The TAIGA facility aims at gamma-ray astrophysics at energies from a few TeV to several PeV and cosmic-ray physics from 100 TeV to several EeV but also pursues searches for astrophysical nanosecond transients, axion-like particles, Lorentz invariance violation and other unexpected manifestations of New Physics. TAIGA-1, a hybrid detector complex with an area of 1 km2, operating since 2021 in the Tunka valley, 50 km to the West from the southernmost tip of lake Baikal, and the plans for its upgrade are presented.

Axion signatures from supernova explosions through the nucleon electric-dipole portal

We consider axions coupled to nucleons and photons only through the nucleon electric-dipole moment (EDM) portal. This coupling is a model-independent feature of QCD axions, which solve the strong $CP$ problem, and might arise as well in more general axionlike particle setups. We revise the supernova (SN) axion emission induced by the nucleon EDM coupling and refine accordingly the SN 1987A bound. Furthermore, we calculate the axion flux from a future Galactic SN and show that it might produce a peculiar and potentially detectable gamma-ray signal in a large underground neutrino detector such as the proposed Hyper-Kamiokande. The possibility to detect such a signal offers a way to search for an oscillating nucleon EDM complementary to CASPERe, without relying on the assumption that axions are a sizeable component of the dark matter. Furthermore, if axions from SN produce an observable signal, they could also lead to an amount of cosmological extra radiation observable in future cosmic surveys.

Searching for axion-like particles with the blazar observations of MAGIC and Fermi-LAT * *Supported by the National Key R&D Program of China (2016YFA0400200) and the National Natural Science Foundation of China (U1738209, 11851303)

In this study, we explore the axion-like particle (ALP)-photon oscillation effect in the γ-ray spectra of the blazars Markarian 421 (Mrk 421) and PG 1553+113, which are measured by the Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) and Fermi Large Area Telescope (Fermi-LAT) with high precision. The Mrk 421 and PG 1553+113 observations of 15 and five phases are used in the analysis, respectively. We find that the combined analysis with all the 15 phases improves the limits of the Mrk 421 observations. For the selected blazar jet magnetic field and extragalactic background light models, the combined limit set by the Mrk 421 observations excludes the ALP parameter region with the ALP-photon coupling of for the ALP mass of at 95% confidence level. The main uncertainties of the analysis originate from the blazar jet magnetic field model. We also find that the ALP hypothesis can slightly improve the fit to the PG 1553+113 results in several parameter regions. We do not set the limit in this case.

Axions from neutron star mergers

Axionlike particles (ALPs) can in principle be produced in very hot and dense astrophysical environments, escape from the extreme object where such conditions are met, and then be converted in gamma rays in the magnetic fields intervening between the event and the Earth. This process potentially offers a new window on both the physics of the axions, and the inner working of the astrophysical objects where they are produced. Interestingly, while this process has been studied for core-collapse supernovae and other extreme astrophysical events, no estimate exists for neutron star mergers, objects recently identified through the detection of gravitational waves. In this work we study the production of ALPs in neutron star mergers, finding that for a large region of the ALP parameter space its magnitude at the source is such to produce a sizable gamma-ray signal at Earth. We show detection forecasts for such events placed in nearby galaxies, finding that they are potentially observable with the Fermi-LAT, thus opening a new window into both the astrophysics of these cataclysmic events, and of new particles beyond the standard model.

Searching for axionlike particles with data scouting at ATLAS and CMS

We investigate the physics case for a dedicated trigger-level analysis for very low mass diphoton resonances at ATLAS and CMS and introduce a new photon isolation criterion. This greatly increases the acceptance for light particles at the expense of a somewhat larger Standard Model background. We show how such an analysis would likely yield new experimental coverage for axionlike particles for masses below 15 GeV, bridging the gap with the region covered by flavor factories.

Low-Energy Supernovae Severely Constrain Radiative Particle Decays.

The hot and dense core formed in the collapse of a massive star is a powerful source of hypothetical feebly interacting particles such as sterile neutrinos, dark photons, axionlike particles (ALPs), and others. Radiative decays such as a→2γ deposit this energy in the surrounding material if the mean free path is less than the radius of the progenitor star. For the first time, we use a supernova (SN) population with particularly low explosion energies as the most sensitive calorimeters to constrain this possibility. These SNe are observationally identified as low-luminosity events with low ejecta velocities and low masses of ejected ^{56}Ni. Their low energies limit the energy deposition from particle decays to less than about 0.1B, where 1 B(bethe)=10^{51} erg. For 1-500MeV-mass ALPs, this generic argument excludes ALP-photon couplings G_{aγγ} in the 10^{-10}-10^{-8} GeV^{-1} range.

Probing light mediators at the MUonE experiment

The MUonE experiment, that aims to provide a precise measurement of the hadronic vacuum polarization contribution to the muon $g-2$ via elastic muon-electron scattering, has also the potential to explore the parameter space of light new physics. Exploiting the process $\mu^- N \to \mu^- N X$, where $N$ is the target nucleus and X is a new physics light mediator, we demonstrate that MUonE can be sensitive to new regions of parameter space for sub-GeV dark photons. In particular, thanks to its muon beam, MUonE will be able to explore uncharted parameter space regions for the $L_\mu-L_\tau$ model. Finally, we also find that MUonE can probe the parameter space of axion-like particles for different assumptions of the couplings to electrons, muons and photons.

Shining ALP dark radiation

String scenarios typically not only predict axion-like particles (ALPs) but also significant amounts of ALP dark radiation originating from the decay of the inflaton or a more general modulus. In this paper, we study the decay of such non-thermally produced relativistic (but massive) ALPs to photons. If the ALPs are sufficiently highly energetic, contribute to $\Delta N_{\rm eff} \gtrsim {\cal O}(0.001)$ and have a mass $m_a\gtrsim$ MeV we find that, using observations of X-, and $\gamma$-rays, the CMB and BBN, very small values of the ALP-photon coupling can be probed, corresponding to an origin of this coupling at the string (or even Planck) scale.