We propose a new axion dark matter detection strategy that employs optical readout of laser beam ellipticity modulations caused by axion-induced electric fields in a microwave cavity, using electro-optic (EO) crystals, enhanced by externally injected radio-frequency (rf) power. Building upon the variance-based probing method [Phys. Rev. D 107, 103005 (2023).], we extend this concept to the optical domain: A weak probe laser interacts with an EO crystal coupled to the resonant microwave cavity field at cryogenic temperatures, and the axion-induced electric field is revealed through induced ellipticity. The injected rf signal coherently interferes with that of the axion field, amplifying the optical response and significantly improving sensitivity. While our EO-based method employs a Fabry-Perot resonator, we do not require Michelson interferometers. Our method, hence, enables compact, high-frequency axion searches, across the 0.5-50 GHz range. Operating at cryogenic temperatures not only suppresses thermal backgrounds, but, critically, allows the probing method to mitigate the quantum noise. This approach offers a scalable path forward for axion detection over the (few-200) & micro;eV mass range-covering the preferred parameter space for the postinflationary Peccei-Quinn axion dark matter-using compact, tunable systems.

Monochromatic high-frequency gravitational waves (HFGWs) provide a distinctive probe of new physics scenarios, most notably axion clouds around rotating black holes formed via superradiance. We reanalyzed data from the CAPP-12T multicell axion haloscope experiment [Kim et al., Phys. Rev. Lett. 133, 051802 (2024)]. The study covers a continuous 2 MHz frequency span centered at 5.311 GHz. No rescan candidates were found, and we set 90% confidence-level exclusion limits on the gravitational-wave strain, reaching h0 approximate to 3.9 & times; 10-21 in the most sensitive regions of the sky. Interpreted in the context of black hole superradiance from axion clouds, the results exclude black holes with mass MBH similar or equal to 1.22 & times; 10-6M circle dot within distances of O(10-2) AU from Earth, under benchmark assumptions. This work demonstrates the potential of electromagnetic resonant cavities as novel detectors of monochromatic HFGWs and motivates future searches for both long-lived and transient signals.

We report a follow-up axion haloscope search near 1.036 GHz that completes and extends our previous work [Ahn et al. Phys. Rev. X 14, 031023 (2024)PRXHAE2160-330810.1103/PhysRevX.14.031023], in which a portion of the HEMT-based data could not be analyzed due to unrecorded experimental information. While recovering this dataset, we identified an excess near 1.036 GHz that satisfied our candidate-selection criteria, motivating dedicated validation studies, including independent cross-checks and reexamination with the original apparatus. The excess did not persist under these investigations and was not confirmed as an axion dark-matter signal. We subsequently extended the search over a 20-MHz band surrounding the candidate using a quantum-noise-limited amplifier, achieving sensitivity close to the Dine-Fischler-Srednicki-Zhitnitsky benchmark. In the absence of a confirmed signal, we set improved 90% confidence-level upper limits on the axion-photon coupling over the frequency range 1.026-1.045 GHz. This Letter highlights the importance of robust candidate-validation strategies as haloscope searches approach discovery-level sensitivity.

Axions and axion-like particles are compelling candidates for ultralight bosonic dark matter, forming coherent oscillating fields that can be probed by experiments known as haloscopes. A broad range of haloscope concepts has been developed, including resonant cavity haloscopes, lumped-element circuit detectors, and spin-based experiments, each sensitive to different axion couplings and mass ranges. Rather than attempting an exhaustive survey of all existing approaches, this comparative review provides a unified framework for the major haloscope classes, establishing a common language for the descriptions of signal generation, noise properties, analytical methodologies, and scanning strategies. Key properties of ultralight bosonic dark matter relevant for detection are summarized first, including coherence time, spectral linewidth, and stochasticity under the standard halo model. The discussion then compares cavity, Earth-scale, lumped-element, and spin haloscopes, focusing on expected signal shapes, dominant noise sources, and statistical frameworks for axion searches. Particular emphasis is placed on consistent definitions of signal-to-noise ratio and on how detector bandwidth, axion coherence, and noise characteristics determine optimal scan strategies. By systematically comparing operating principles and performance metrics across these detector families, this framework clarifies shared concepts as well as the essential differences that govern sensitivity in different mass and coupling regimes. The resulting perspective synthesizes current search methodologies and offers guidance for optimizing future haloscope experiments.

Josephson parametric amplifiers (JPAs) are used in a wide range of applications, including quantum sensing and axion dark matter searches, due to their near-quantum-limited noise performance. In this article, we present a novel amplifier configuration that increases the frequency scanning range for axion search experiments by combining six narrow-band, flux-driven JPAs. The design consists of two subsets, each comprising three JPAs connected in parallel and coupled to one of two circulators. These subsets are arranged in series. A single pump tone is split and distributed across all JPAs. We effectively mitigated challenges associated with frequency tuning and cross-talk arising from JPA band overlap while maintaining low noise performance. To validate this configuration, we implemented a JPA system spanning 1.2-1.5 GHz as the first-stage amplifier in an RF chain, where the total noise was measured to be approximately twice the standard quantum limit.

The proposed proton electric dipole moment (pEDM) experiment at Brookhaven National Laboratory (BNL), to be built inside the alternating gradient synchrotron (AGS) tunnel, aims to measure the proton's electric dipole moment with a sensitivity of 10-29 e cm. This paper presents the design of the injection line from the AGS booster to the pEDM storage ring, utilizing portions of the existing booster-to-AGS (BtA) transfer line. Building on the symmetric-hybrid lattice design [Z. Omarov et al., Comprehensive symmetric-hybrid ring design for a proton-EDM experiment at below 10-29 e cm, Phys. Rev. D 105, 032001 (2022)], our study emphasizes rigorous optics matching, detailed particle and spin tracking, and systematic error mitigation essential for achieving a target sensitivity of 10-29 e cm. This design preserves the proton's vertical spin orientation within +20 mrad, a critical requirement for the pEDM measurement. Particle and spin tracking simulations using the ray-tracing code Zgoubi [F. Meot, Zgoubi users' guide, Upton, NY, 2012] validate the design's performance, demonstrating its feasibility for this precision experiment. The simulation results demonstrate that both clockwise (CW) and counterclockwise (CCW) injection lines meet the stringent beam envelope and polarization requirements.

Axion haloscopes use radio-frequency cavities immersed in a magnetic field to search for dark-matter axions, which could resolve two central puzzles in fundamental physics: the strong charge-parity problem in quantum chromodynamics and the nature of dark matter. Multi-tesla fields trigger axion-to-photon conversion but induce severe vortex dissipation in standard superconductors, whereas copper cavities are limited by the anomalous skin effect (Q ≲ 10^5). Here, we overcome these barriers by introducing a pole-to-pole 3-dimensional cavity architecture constructed from strain-controlled, mechanically delaminated rare-earth barium copper oxide (REBCO) tapes. By selectively stripping the lossy metallic substrate while utilizing the copper stabilizer as a "conductive backing" we convert the longitudinal assembly gaps into waveguides below cutoff, effectively suppressing cross-seam RF leakage. Employing a two-track strategy, we first unveiled the intrinsic high-field potential of the material with a 5.4 GHz resonant cavity, achieving an unloaded quality-factor (Q_0) of 1.4 × 10^7 in an 8 T magnetic field, exceeding conventional copper baselines by two orders of magnitude. Second, prioritizing practical haloscope integration, we engineered a tunable, volume-maximized 2.3 GHz pathfinder cavity. Deployed in the Pilot Axion Cavity Experiment at the Center for Axion and Precision Physics Research (CAPP-PACE), this system achieved a 180 mK noise temperature and a 5-fold Q enhancement over copper, cumulatively delivering a ∼8.4-fold scan-rate acceleration.

We report on a search for a gravitationally bound solar axion halo using data from the global network of optical magnetometers for exotic physics searches (GNOME), a worldwide array of magnetically shielded atomic magnetometers with sensitivity to exotic spin couplings. Motivated by recent theoretical work suggesting that self-interacting ultralight axions can be captured by the Sun's gravitational field and thermalize into the ground state, we develop a signal model for the pseudomagnetic fields generated by axion-proton gradient couplings in such a halo. The analysis focuses on the fifth GNOME Science Run (69 days, 12 stations), employing a cross-correlation pipeline with time-shifted daily modulation templates to search for the global, direction-dependent, monochromatic signal expected from a solar axion halo. No statistically significant candidate signals are observed. We set 95% confidence-level upper limits on the amplitude of the axion-induced pseudomagnetic field over the frequency range approximate to 0.05-20 Hz, translating to constraints on the linear and quadratic axion-proton couplings for halo densities predicted by gravitational capture models and for the maximum overdensities allowed by planetary ephemerides. In the quadratic coupling case, our limits surpass existing astrophysical bounds by over two orders of magnitude across much of the accessible parameter space.

Precision measurements in storage rings are increasingly limited by the ability to monitor collective spin dynamics coherently over long time scales. Existing polarimetry techniques rely on destructive scattering processes that preclude continuous, non-intercepting tracking of spin evolution and constrain both statistical sensitivity and systematic control. Here we introduce a non-destructive, phase-coherent polarimetry method in which the stored beam polarization is treated as a continuous dynamical observable rather than a quantity inferred from scattering events. Spin-dependent electromagnetic fields generated by a polarized relativistic beam establish a symmetry-selected differential signal on pickup electrodes. This signal is transduced into a narrowband phase modulation of a high-Q resonator interrogated with a coherent probe, while dominant charge-induced backgrounds are rejected through geometric symmetry, helicity reversal, and synchronous demodulation. Controlled spin precession (spin-wheel operation) provides a stable phase reference enabling phase-coherent detection of slow spin evolution. Combined with optimized lattice symmetry and beam cooling, this approach can substantially extend the usable spin coherence time, with values approaching 10^5 s appearing realistic within existing accelerator technology. The resulting readout supports optimal slope-based estimation with T^-3/2 statistical scaling while eliminating the efficiency penalties inherent to scattering-based polarimetry. For storage-ring EDM experiments, this combination enables sensitivity approaching the level expected within the Standard Model. More broadly, the method establishes a general phase-coherent architecture for collective spin measurements in storage rings, adapting resonant sensing concepts from axion dark-matter searches to charged-particle precision experiments.

Conventional high-mass axion haloscopes based on the TM_010 mode lose detection volume as the resonant frequency increases. We report an extended axion search using a dielectric-restored TM_020 cavity haloscope with symmetry-preserving auxetic tuning based on a single-degree-of-freedom mechanical architecture. Using a near-quantum-limited microwave receiver, we searched a frequency range of 4.98-5.07 GHz and exclude axion-photon couplings with sensitivity approaching the KSVZ benchmark. Together with two earlier searches, the present scans extend a multi-scan program based on this architecture, yielding nearly 300 MHz of contiguous high-mass axion coverage over 4.98-5.27 GHz, the first broad search reported with a single higher-order-mode haloscope. This work establishes higher-order-mode cavities as a practical, scalable route beyond the TM_010 volume penalty.

We report on a search for axion dark matter in the frequency range near 5.9 GHz, conducted using the haloscope technique. The experiment employed an 8-cell microwave resonator designed to extend the accessible frequency range by a multifold factor relative to conventional single-cell configurations, while maintaining a large detection volume. To enhance sensitivity, a flux-driven Josephson parametric amplifier operating near the quantum noise limit was utilized, together with a sideband-summing method that coherently combines mirrored spectral components generated by the Josephson parametric amplifier. Data were acquired over the frequency range 5.83–5.94 GHz. With no statistically significant excess observed, we exclude axion-photon couplings g a γ γ down to 1.2 × 10 − 14 GeV − 1 at a 90% confidence level. The achieved sensitivity approaches the Kim-Shifman-Vainshtein-Zakharov benchmark prediction, setting the most stringent limits to date in this range.

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 Omega dark Omega visible. In this framework, the population of galactic axions with mass 10-6 eV ma 10-3 eV and velocity hvai 10-3c will be accompanied by axions with typical velocities hvai 0.6c emitted by AQNs. Furthermore, in this framework, it has also been argued that the AQN-induced axion daily modulation (in contrast with the conventional weakly interactive massive particle paradigm) could be as large as (10-20)%, representing 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.

Dark matter remains one of the most profound mysteries in modern physics, with axions, a hypothetical particle proposed to resolve the strong CP problem, standing as a compelling candidate. Among various experimental strategies, cavity haloscopes currently offer the most sensitive method to detect axions, though their searches have largely been confined to axion masses below 10 μeV. However, recent theoretical developments suggest that the axion mass lies beyond this range. Higher-order cavity modes have been explored as a methodological approach to expand the search range, albeit with limited success in achieving both high sensitivity and broad tunability. In this work, we present a sensitive search for axions with masses around 21 μeV, utilizing the TM_020 mode of a cylindrical cavity, which incorporated an innovative tuning mechanism. Our results reached 1.7 times the KSVZ sensitivity over 100 MHz, representing a significant improvement in this mass range and contributing to the experimental search for axion dark matter at higher masses.

We present the development of two complementary amplifier architectures for axion haloscope experiments, based on two types of Josephson Parametric Amplifiers (JPAs). The first employs a multi-chip module of flux-driven JPAs in a parallel–series configuration, enabling near quantum-limited amplification over an extended tunable range of between 1.2 and 1.5 GHz. The second design features a lumped-element JPA, offering continuous tunability across a wide frequency range from 2.4 to 4 GHz. Both approaches demonstrate near-quantum-limited noise performance and are compatible with operation in cryogenic environments. These amplifiers significantly enhance the sensitivity and frequency coverage of axion search experiments, and also provide new opportunities for broadband quantum sensing applications.

Dunkle Materie (DM) came from unexpected cosmological observations. Nowadays within our solar system, diverse observations also defy conventional explanations, like the main physical process(es) underlying the heating of the different solar atmospheric layers. Streaming DM offers a viable common scenario following gravitational focusing by the solar system bodies. This fits as the underlying process behind the solar cycle, which was the first signature suggesting a planetary dependency. The challenge, since 1859, is to find a remote planetary impact, beyond the extremely feeble planetary tidal force. We stress the possible involvement of an external impact by some overlooked "streaming invisible matter", which reconciles all investigated mysterious observations mimicking a not extant remote planetary force. Unexpected planetary relationships exist for both the dynamic Sun and Earth, reflecting multiple signatures for streaming DM. The local reasoning & agrave; la Zwicky is also suggestive for searches including puzzling biomedical phenomena. Favorite DM candidates are anti-quark-nuggets, magnetic monopoles, dark photons, or the composite "pearls". Then, anomalies within the solar system are the manifestation of the dark Universe. The tentative streaming DM scenario enhances spatiotemporally the DM flux favouring conditions for direct DM detection or extracting energy from the not-so-invisible as anticipated dark sector.

We propose a new axion dark matter detection strategy that employs optical readout of laser beam ellipticity modulations caused by axion-induced electric fields in a microwave cavity, using electro-optic (EO) crystals, enhanced by externally injected radio-frequency (RF) power. Building upon the variance-based probing method, PRD 107, 103005, (2023), we extend this concept to the optical domain: a weak probe laser interacts with an EO crystal placed inside a resonant microwave cavity at cryogenic temperatures, and the axion-induced electric field is revealed through induced ellipticity. The injected RF signal coherently interferes with that of the axion field, amplifying the optical response and significantly improving sensitivity. While our EO-based method employs a Fabry-Perot resonator, we do not require Michelson interferometers. Our method hence enables compact, high-frequency axion searches, across the 0.5-50 GHz range. Operating at cryogenic temperatures not only suppresses thermal backgrounds but, critically, allows the probing method to mitigate the laser quantum noise. This approach offers a scalable path forward for axion detection over the ∼ (few-200) μeV mass range – covering the preferred parameter space for the post-inflationary Peccei-Quinn axion dark matter – using compact, tunable systems.

The Proton EDM Experiment (pEDM) is the first direct search for the proton electric dipole moment (EDM) with the aim of being the first experiment to probe the Standard Model (SM) prediction of any particle EDM. Phase-I of pEDM will achieve 10^-29 e·cm, improving current indirect limits by four orders of magnitude. This will establish a new standard of precision in nucleon EDM searches and offer a unique sensitivity to better understand the Strong CP problem. The experiment is ideally positioned to explore physics beyond the Standard Model (BSM), with sensitivity to axionic dark matter via the signal of an oscillating proton EDM and across a wide mass range of BSM models from 𝒪(1GeV) to 𝒪(10^3TeV). Utilizing the frozen-spin technique in a highly symmetric storage ring that leverages existing infrastructure at Brookhaven National Laboratory (BNL), pEDM builds upon the technological foundation and experimental expertise of the highly successful Muon g-2 Experiments. With significant R&D and prototyping already underway, pEDM is preparing a conceptual design report (CDR) to offer a cost-effective, high-impact path to discovering new sources of CP violation and advancing our understanding of fundamental physics. It will play a vital role in complementing the physics goals of the next-generation collider while simultaneously contributing to sustaining particle physics research and training early-career researchers during gaps between major collider operations.

The axion quark nugget (AQN) model is an emerging candidate for cold dark matter, and proposes that dark matter consists of (anti)quarks in a color superconducting state enclosed by an axion domain wall. We performed the first dedicated AQN experiment using an axion haloscope, based on the scenario that antimatter AQNs could annihilate with Earth matter and release relativistic axions. This experiment employed a high-temperature superconducting microwave cavity that achieved a quality factor exceeding one million in a strong magnetic field, alongside a quantum-noise-limited Josephson parametric amplifier. Combined with an additional experiment using a large-volume copper cavity, our investigation focused on the range of axion rest mass between 1.9 mu eV and 9.3 mu eV, and attempted to detect the daily modulation of the signal predicted by the model. While no definitive signals were detected, this study establishes the initial groundwork for exploring broader parameter spaces in future experiments.

Axions, originally proposed to resolve the CP problem in the strong interaction, remain a leading dark matter candidate. While cavity haloscopes offer the most sensitive technique for detecting axions, searches have largely been limited to masses below 10  μeV. We report a sensitive search for axion dark matter with masses around 21  μeV, utilizing the TM_{020} mode of a cylindrical cavity equipped with an innovative tuning mechanism. Our search achieved a sensitivity of 1.7× the Kim-Shifman-Vainshtein-Zakharov benchmark over a 100-MHz range, representing a significant advance in this mass range. These results demonstrate that higher-order modes provide a viable strategy for extending haloscope searches into previously unexplored higher-mass regions.