Explore the vast range of titles available.

The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole magnet, has searched for axions in the 19.74  μ eV to 22.47  μ eV mass range. The detection concept follows the Sikivie haloscope principle, where Dark Matter axions convert into photons within a resonator immersed in a magnetic field. The CAST-CAPP resonator is an array of four individual rectangular cavities inserted in a strong dipole magnet, phase-matched to maximize the detection sensitivity. Here we report on the data acquired for 4124 h from 2019 to 2021. Each cavity is equipped with a fast frequency tuning mechanism of 10 MHz/ min between 4.774 GHz and 5.434 GHz. In the present work, we exclude axion-photon couplings for virialized galactic axions down to g a γ γ  = 8 × 10 −14 GeV −1 at the 90% confidence level. The here implemented phase-matching technique also allows for future large-scale upgrades. Haloscopes aim at detecting axions by converting them into photons using high-quality resonant cavities, where the cavity resonance should be tuned with the unknown axion mass. Here, the authors improve exclusion limits using four phase-matched resonant cavities and a fast frequency scanning technique.

This article describes BabyIAXO, an intermediate experimental stage of the International Axion Observatory (IAXO), proposed to be sited at DESY. IAXO is a large-scale axion helioscope that will look for axions and axion-like particles (ALPs), produced in the Sun, with unprecedented sensitivity. BabyIAXO is conceived to test all IAXO subsystems (magnet, optics and detectors) at a relevant scale for the final system and thus serve as prototype for IAXO, but at the same time as a fully-fledged helioscope with relevant physics reach itself, and with potential for discovery. The BabyIAXO magnet will feature two 10 m long, 70 cm diameter bores, and will host two detection lines (optics and detector) of dimensions similar to the final ones foreseen for IAXO. BabyIAXO will detect or reject solar axions or ALPs with axion-photon couplings down to gaγ ∼ 1.5 × 10-11 GeV-1, and masses up to ma ∼ 0.25 eV. BabyIAXO will offer additional opportunities for axion research in view of IAXO, like the development of precision x-ray detectors to identify particular spectral features in the solar axion spectrum, and the implementation of radiofrequency-cavity-based axion dark matter setups.

Abstract We present a search for solar axions produced through the axion-electron coupling (g ae ) using data from a novel 7-GridPix detector installed at the CERN Axion Solar Telescope (CAST). The detector, featuring ultra-thin silicon nitride windows and multiple veto systems, collected approximately 160 hours of solar tracking data between 2017–2018. Using machine learning techniques and the veto systems, we achieved a background rate of 1.06 × 10 −5 keV −1 cm −2 s −1 at a signal efficiency of about 80% in the 0.2 to 8 keV range. Analysis of the data yielded no significant excess above background, allowing us to set a new upper limit on the product of the axion-electron and axion-photon couplings of g ae · g aγ < 7.35 × 10 −23 GeV −1 at 95% confidence level for axion masses below 10 meV. This result improves upon the previous best helioscope limit and demonstrates the potential of GridPix technology for rare event searches. Additionally, we derived a limit on the axion-photon coupling of g aγ < 9.0 × 10 −11 GeV −1 at 95% CL, which, while not surpassing CAST’s best limit, provides complementary constraints on axion models.

Background: we develop the concept of a Micromegas (MICRO-MEsh GAseous Structure) readout plane with an additional GEM (Gas Electron Multiplier) preamplification stage placed a few mm above it, to increase the maximum effective gain of the combined readout. We implement it and test it in realistic conditions for its application to low-background dark matter searches like the TREX-DM experiment. Methods: for this, we use a Micromegas of microbulk type, built with radiopure materials. A small test chamber allowing for systematic scanning of voltages and pressures is used. In addition, a TREX-DM full-scale set-up has also been built and tested, featuring a replica of the fully-patterned TREX-DM microbulk readout. Results: we report on GEM effective extra gain factors of about 90, 50 and 20 in 1, 4 and 10 bar of Ar-1%iC\\(_4\\)H\\(_10\\). Conclusions: the results here obtained show promise to lower the threshold of the experiment down to 50 eV\\(_ee\\), corresponding to substantially enhanced sensitivity to low-mass WIMPs (Weakly Interacting Massive Particles).

It has been previously advocated that the presence of the daily and annual modulations of the axion flux on the Earth's surface may dramatically change the strategy of the axion searches. The arguments were based on the so-called Axion Quark Nugget (AQN) dark matter model which was originally put forward to explain the similarity of the dark and visible cosmological matter densities \\(_ dark _ visible\\). In this framework, the population of galactic axions with mass \\( 10^-6 eV m_a 10^-3 eV\\) and velocity \\( v_a 10^-3 c\\) will be accompanied by axions with typical velocities \\( v_a 0.6 c\\) emitted by AQNs. Furthermore, in this framework, it has also been argued that the AQN-induced axion daily modulation (in contrast with the conventional WIMP paradigm) could be as large as \\((10-20)\\%\\), which represents the main motivation for the present investigation. We argue that the daily modulations along with the broadband detection strategy can be very useful tools for the discovery of such relativistic axions. The data from the CAST-CAPP detector have been used following such arguments. Unfortunately, due to the dependence of the amplifier chain on temperature-dependent gain drifts and other factors, we could not conclusively show the presence or absence of a dark sector-originated daily modulation. However, this proof of principle analysis procedure can serve as a reference for future studies.

Hypothetical axions provide a compelling explanation for dark matter and could be emitted from the hot solar interior. The CERN Axion Solar Telescope (CAST) has been searching for solar axions via their back conversion to X-ray photons in a 9-T 10-m long magnet directed towards the Sun. We report on an extended run with the IAXO (International Axion Observatory) pathfinder detector, doubling the previous exposure time. The detector was operated with a xenon-based gas mixture for part of the new run, providing technical insights for future detector configurations in IAXO. No counts are detected in the 95% signal-encircling region during the new run, while 0.75 are expected. The new data improve the axion-photon coupling limit to 5.8\\(\\times 10^{-11}\\,\\)GeV\\(^{-1}\\) at 95% C.L. (for \\(m_a \\lesssim 0.02\\) eV), the most restrictive experimental limit to date.

Rare event searches require extreme radiopurity in all detector components. This includes the active medium, which in the case of gaseous detectors, is the operating gas. The gases used typically include noble gas mixtures with molecular quenchers. Purification of these gases is required to achieve the desired detector performance, however, purifiers are known to emanate 222 Rn, which is a potential source of background. Several purifiers are studied for their O 2 and H 2 O purification efficiency and Rn emanation rates, aiming to identify the lowest-Rn options. Furthermore, the absorption of quenchers by the purifiers is assessed when used in a recirculating closed-loop gas system.

We report on the successful implementation of an \\(^{37}\\)Ar calibration source in the TREX-DM detector, a high-pressure time projection chamber designed for low-mass dark matter searches. The \\(^{37}\\)Ar source was produced through fast neutron activation of CaO powder at the HiSPANoS facility of Centro Nacional de Aceleradores (CNA) in Spain, yielding \\(O(1)\\) kBq of activity. Using a novel combined GEM-Micromegas readout system, we successfully detected both characteristic emissions from \\(^{37}\\)Ar decay (2.82 keV and 270 eV) and achieved unprecedented energy threshold performance in TREX-DM, approaching the single-electron ionization energy of argon.

The spatial resolution of the Micromegas prototype developed for the BabyIAXO experiment was evaluated using a low-energy X-ray beam at the SOLEIL synchrotron facility. BabyIAXO, currently under construction, aims to search for hypothetical solar axions. A key component of the experiment is a low-background X-ray detector with high efficiency in the 1-10 keV energy range and stringent background rejection capabilities. Achieving a spatial resolution on the order of, or better than, 1 mm is critical for accurately reconstructing signal shapes and positions, and for effectively discriminating between signal and background events. Therefore, a precise characterization of the detector's spatial resolution is essential to validate its suitability for the experiment. This study involved scanning the IAXO-D1 Micromegas detector under various beam energies, positions, and drift field configurations to evaluate their influence on spatial resolution. A resolution of approximately 100 \\(\\mu\\)m at 6 keV was achieved, confirming the strong potential of this technology for application in the final BabyIAXO setup.

The CAST-CAPP axion haloscope, operating at CERN inside the CAST dipole magnet, has searched for axions in the 19.74 \\(\\mu\\)eV to 22.47 \\(\\mu\\)eV mass range. The detection concept follows the Sikivie haloscope principle, where Dark Matter axions convert into photons within a resonator immersed in a magnetic field. The CAST-CAPP resonator is an array of four individual rectangular cavities inserted in a strong dipole magnet, phase-matched to maximize the detection sensitivity. Here we report on the data acquired for 4124 h from 2019 to 2021. Each cavity is equipped with a fast frequency tuning mechanism of 10 MHz/min between 4.774 GHz and 5.434 GHz. In the present work, we exclude axion-photon couplings for virialized galactic axions down to \\(g_{a{\\gamma}{\\gamma}} = 8 \\times {10^{-14}}\\) \\(GeV^{-1}\\) at the 90% confidence level. The here implemented phase-matching technique also allows for future large-scale upgrades.