arXiv subjects

Javier Redondo

Publications and source records attributed to Javier Redondo.

At least 37 records · Page 2Linked to original sources

arXiv2019

Weighing the Solar Axion

Axion helioscopes search for solar axions and axion-like particles via inverse Primakoff conversion in strong laboratory magnets pointed at the Sun. While helioscopes can always measure the axion coupling to photons, the conversion signal is independent of the mass for axions lighter than around 0.02 eV. Masses above this value on the other hand have suppressed signals due to axion-photon oscillations which destroy the coherence of the conversion along the magnet. However, the spectral oscillations present in the axion conversion signal between these two regimes are highly dependent on the axion mass. We show that these oscillations are observable given realistic energy resolutions and can be used to determine the axion mass to within percent level accuracies. Using projections for the upcoming helioscope IAXO, we demonstrate that $>3σ$ sensitivity to a non-zero axion mass is possible between $3 \times 10^{-3}$ and $10^{-1}$ eV for both the Primakoff and axion-electron solar fluxes.

hep-ph↗

arXiv2018

Directional axion detection

We develop a formalism to describe extensions of existing axion haloscope designs to those that possess directional sensitivity to incoming dark matter axion velocities. The effects are measurable if experiments are designed to have dimensions that approach the typical coherence length for the local axion field. With directional sensitivity, axion detection experiments would have a greatly enhanced potential to probe the local dark matter velocity distribution. We develop our formalism generally, but apply it to specific experimental designs, namely resonant cavities and dielectric disk haloscopes. We demonstrate that these experiments are capable of measuring the daily modulation of the dark matter signal and using it to reconstruct the three-dimensional velocity distribution. This allows one to measure the Solar peculiar velocity, probe the anisotropy of the dark matter velocity ellipsoid and identify cold substructures such as the recently discovered streams near to Earth. Directional experiments can also identify features over much shorter timescales, potentially facilitating the mapping of debris from axion miniclusters.

astro-ph.CO↗

arXiv2018

Dielectric haloscopes: sensitivity to the axion dark matter velocity

We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass ($40-400~μ$eV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20% of the axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity, and thus a sensitive measure of axion astrophysics.

hep-ph↗

arXiv2018

Enhanced 3D-printed holographic acoustic lens for aberration correction of single-element transcranial focused ultrasound

The correction of the aberration of transcranial focused ultrasounds is a relevant issue for enhancing various non-invasive medical treatments. Emission through multi-element phased arrays has been the most widely accepted method to reduce aberrations in recent years; however, a new disruptive technology, based on 3D printed acoustic lenses, has recently been proposed with lower cost and comparable accuracy. The number and size of transducers in phased array configurations was a bottleneck limiting the focusing accuracy, but once the submillimeter precision of the latest generation 3D printers has overcome this limitation, the challenge is now to improve the accuracy of the numerical simulations needed to design the lens. This study introduces and evaluates two improvements to the numerical model applied in previous works that proposed 3D lenses, which consist in the direct calculation of the phase pattern from the propagation of oscillating magnitudes in complex form, and in the introduction of the absorption phenomenon into the set of equations that describe the dynamics of the wave in both fluid and solid media. Numerical experiments are performed analysing the quality of the aberrated-corrected focus in different configurations. The results obtained show that the inclusion of absorption significantly improves focusing, especially where the thickness of the skull is more irregular.

physics.med-ph↗

arXiv2018

Axion Searches with Microwave Filters: the RADES project

We propose, design and construct a variant of the conventional axion haloscope concept that could be competitive in the search for dark matter axions of masses in the decade 10-100 $μ$eV. Theses masses are located somewhat above the mass range in which existing experiments have reached sensitivity to benchmark QCD axion models. Our haloscope consists of an array of small microwave cavities connected by rectangular irises, in an arrangement commonly used in radio-frequency filters. The size of the unit cavity determines the main resonant frequency, while the possibility to connect a {large} number of cavities allows to reach large detection volumes. We develop the theoretical framework of the detection concept, and present design prescriptions to optimize detection capabilities. We describe the design and realization of a first small-scale prototype of this concept, called Relic Axion Detector Exploratory Setup (RADES). It consists of a copper-coated stainless steel five-cavities microwave filter with the detecting mode operating at around 8.4 GHz. This structure has been electromagnetically characterized at 2 K and 298 K, and it is now placed in ultra-high vacuum in one of the twin-bores of the 9 T CAST dipole magnet at CERN. We describe the data acquisition system developed for relic axion detection, and present preliminary results of the electromagnetic properties of the microwave filter, which show the potential of filters to reach QCD axion window sensitivity at X-band frequencies.

hep-ex↗

arXiv2018

New experimental approaches in the search for axion-like particles

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

hep-ph↗

arXiv2017

Solar neutrino flux at keV energies

We calculate the solar neutrino and antineutrino flux in the keV energy range. The dominant thermal source processes are photoproduction ($γe\to e ν\barν$), bremsstrahlung ($e+Ze\to Ze+e+ν\barν$), plasmon decay ($γ\toν\barν$), and $ν\barν$ emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. These latter processes dominate in the energy range of a few keV and thus carry information about the solar metallicity. To calculate their rate we use libraries of monochromatic photon radiative opacities in analogy to a previous calculation of solar axion emission. Our overall flux spectrum and many details differ significantly from previous works. While this low-energy flux is not measurable with present-day technology, it could become a significant background for future direct searches for keV-mass sterile neutrino dark matter.

hep-ph↗

arXiv2017

Dilute and dense axion stars

Axion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillating solutions to their classical equation of motion. Depending on the value of the field amplitude at the core $|θ_0| \equiv |θ(r=0)|$, the equilibrium of the system arises from the balance of the kinetic pressure and either self-gravity or axion self-interactions. Starting from a general relativistic framework, we obtain the set of equations describing the configuration of the axion star, which we solve as a function of $|θ_0|$. For small $|θ_0| \lesssim 1$, we reproduce results previously obtained in the literature, and we provide arguments for the stability of such configurations in terms of first principles. We compare qualitative analytical results with a numerical calculation. For large amplitudes $|θ_0| \gtrsim 1$, the axion field probes the full non-harmonic QCD chiral potential and the axion star enters the {\it dense} branch. Our numerical solutions show that in this latter regime the axions are relativistic, and that one should not use a single frequency approximation, as previously applied in the literature. We employ a multi-harmonic expansion to solve the relativistic equation for the axion field in the star, and demonstrate that higher modes cannot be neglected in the dense regime. We interpret the solutions in the dense regime as pseudo-breathers, and show that the life-time of such configurations is much smaller than any cosmological time scale.

astro-ph.CO↗

arXiv2017

Solar neutrinos at keV energies: thermal flux

The neutrino flux at Earth is dominated in the keV energy range by the neutrinos produced in the Sun through thermal processes, namely photo production, bremsstrahlung, plasmon decay, and emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. Such a component of the neutrino flux is conspicuously absent from popular analyses of the all-sources spectrum at Earth, whereas if detected it could be a source of information about solar physics. Moreover, it would be the relevant background for keV-mass sterile neutrino dark matter direct searches.

hep-ph↗

arXiv2017

Stellar Recipes for Axion Hunters

There are a number of observational hints from astrophysics which point to the existence of stellar energy losses beyond the ones accounted for by neutrino emission. These excessive energy losses may be explained by the existence of a new sub-keV mass pseudoscalar Nambu--Goldstone boson with tiny couplings to photons, electrons, and nucleons. An attractive possibility is to identify this particle with the axion -- the hypothetical pseudo Nambu--Goldstone boson predicted by the Peccei--Quinn solution to the strong CP problem. We explore this possibility in terms of a DFSZ-type axion and of a KSVZ-type axion/majoron, respectively. Both models allow a good global fit to the data, prefering an axion mass around 10 meV. We show that future axion experiments -- the fifth force experiment ARIADNE and the helioscope IAXO -- can attack the preferred mass range from the lower and higher end, respectively. An axion in this mass range can also be the main constituent of dark matter.

hep-ph↗

arXiv2017

Standard Model-Axion-Seesaw-Higgs Portal Inflation. Five problems of particle physics and cosmology solved in one stroke

We present a minimal extension of the Standard Model (SM) providing a consistent picture of particle physics from the electroweak scale to the Planck scale and of cosmology from inflation until today. Three right-handed neutrinos $N_i$, a new color triplet $Q$ and a complex SM-singlet scalar $σ$, whose vacuum expectation value $v_σ\sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously, are added to the SM. At low energies, the model reduces to the SM, augmented by seesaw generated neutrino masses and mixing, plus the axion. The latter solves the strong CP problem and accounts for the cold dark matter in the Universe. The inflaton is comprised by a mixture of $σ$ and the SM Higgs, and reheating of the Universe after inflation proceeds via the Higgs portal. Baryogenesis occurs via thermal leptogenesis. Thus, five fundamental problems of particle physics and cosmology are solved at one stroke in this unified Standard Model - Axion - seesaw - Higgs portal inflation (SMASH) model. It can be probed decisively by upcoming cosmic microwave background and axion dark matter experiments.

hep-ph↗

arXiv2017

Dielectric Haloscopes: A New Way to Detect Axion Dark Matter

We propose a new strategy to search for dark matter axions in the mass range of 40--400 $μ$eV by introducing dielectric haloscopes, which consist of dielectric disks placed in a magnetic field. The changing dielectric media cause discontinuities in the axion-induced electric field, leading to the generation of propagating electromagnetic waves to satisfy the continuity requirements at the interfaces. Large-area disks with adjustable distances boost the microwave signal (10--100 GHz) to an observable level and allow one to scan over a broad axion mass range. A sensitivity to QCD axion models is conceivable with 80 disks of 1 m$^2$ area contained in a $10$ Tesla field.

physics.ins-det↗

arXiv2017

Unifying inflation with the axion, dark matter, baryogenesis and the seesaw mechanism

A minimal extension of the Standard Model (SM) with a single new mass scale and providing a complete and consistent picture of particle physics and cosmology up to the Planck scale is presented. We add to the SM three right-handed SM-singlet neutrinos, a new vector-like color triplet fermion and a complex SM singlet scalar $σ$ that stabilises the Higgs potential and whose vacuum expectation value at $\sim 10^{11}$ GeV breaks lepton number and a Peccei-Quinn symmetry simultaneously. Primordial inflation is produced by a combination of $σ$ (non-minimally coupled to the scalar curvature) and the SM Higgs. Baryogenesis proceeds via thermal leptogenesis. At low energies, the model reduces to the SM, augmented by seesaw-generated neutrino masses, plus the axion, which solves the strong CP problem and accounts for the dark matter in the Universe. The model predicts a minimum value of the tensor-to-scalar ratio $r\simeq 0.004$, running of the scalar spectral index $α\simeq - 7\times 10^{-4}$, the axion mass $m_A\sim 100\,μ{\rm eV}$ and cosmic axion background radiation corresponding to an increase of the effective number of relativistic neutrinos of $\sim 0.03$. It can be probed decisively by the next generation of cosmic microwave background and axion dark matter experiments.

hep-ph↗

arXiv2017

Dielectric Haloscopes to Search for Axion Dark Matter: Theoretical Foundations

We study the underlying theory of dielectric haloscopes, a new way to detect dark matter axions. When an interface between different dielectric media is inside a magnetic field, the oscillating axion field acts as a source of electromagnetic waves, which emerge in both directions perpendicular to the surface. The emission rate can be boosted by multiple layers judiciously placed to achieve constructive interference and by a large transverse area. Starting from the axion-modified Maxwell equations, we calculate the efficiency of this new dielectric haloscope approach. This technique could potentially search the unexplored high-frequency range of 10--100 GHz (axion mass 40--400 $μ$eV), where traditional cavity resonators have difficulties reaching the required volume.

hep-ph↗

arXiv2016

MADMAX: A new Dark Matter Axion Search using a Dielectric Haloscope

The axion is an intriguing dark matter candidate emerging from the Peccei-Quinn solution to the strong CP problem. Current experimental searches for axion dark matter focus on the axion mass range below 40 $μ$eV. However, if the Peccei-Quinn symmetry is restored after inflation the observed dark matter density points to an axion mass around 100 $μ$eV. A new project based on axion-photon conversion at the transition between different dielectric media is presented. By using $\sim 80$ dielectric discs, the emitted power could be enhanced by a factor of $\sim 10^5$ over that from a single mirror (flat dish antenna). Within a 10 T magnetic field, this could be enough to detect $\sim 100 μ$eV axions with HEMT linear amplifiers. The design for an experiment is proposed. Results from noise, transmissivity and reflectivity measurements obtained in a prototype setup are presented. The expected sensitivity is shown.

astro-ph.IM↗

arXiv2016

Cool WISPs for stellar cooling excesses

Several stellar systems (white dwarfs, red giants, horizontal branch stars and possibly the neutron star in the supernova remnant Cassiopeia A) show a mild preference for a non-standard cooling mechanism when compared with theoretical models. This exotic cooling could be provided by Weakly Interacting Slim Particles (WISPs), produced in the hot cores and abandoning the star unimpeded, contributing directly to the energy loss. Taken individually, these excesses do not show a strong statistical weight. However, if one mechanism could consistently explain several of them, the hint could be significant. We analyze the hints in terms of neutrino anomalous magnetic moments, minicharged particles, hidden photons and axion-like particles (ALPs). Among them, the ALP or a massless HP represent the best solution. Interestingly, the hinted ALP parameter space is accessible to the next generation proposed ALP searches, such as ALPS II and IAXO and the massless HP requires a multi TeV energy scale of new physics that might be accessible at the LHC.

astro-ph.HE↗

arXiv2016

Hidden Photons in Aharonov-Bohm-Type Experiments

We discuss the Aharonov-Bohm effect in the presence of hidden photons kinetically mixed with the ordinary electromagnetic photons. The hidden photon field causes a slight phase shift in the observable interference pattern. It is then shown how the limited sensitivity of this experiment can be largely improved. The key observation is that the hidden photon field causes a leakage of the ordinary magnetic field into the supposedly field-free region. The direct measurement of this magnetic field can provide a sensitive experiment with a good discovery potential, particularly below the $\sim$ meV mass range for hidden photons.

hep-ph↗

arXiv2016

Axions at the International Axion Observatory

QCD axions with meV mass can be behind some stellar cooling anomalies and form all or part of the cold dark matter of the universe. We discuss on a proposed experiment to discover the solar flux of meV mass axions: the International AXion Observatory: IAXO.

hep-ph↗