arXiv subjects

Abaz Kryemadhi

Publications and source records attributed to Abaz Kryemadhi.

10 recordsLinked to original sources

arXiv2026

First limits on axion dark matter from a DALI prototype

We report a pilot dark matter search with a cryogenic, magnetized, scaled-down DALI prototype. An analysis of 36 hours of data reveals no statistically significant excess attributable to axionlike particles. We therefore set new exclusion limits in the 6.88691--6.91792 GHz band, reaching an axion-photon coupling sensitivity of $g_{aγγ}\lesssim 9.7\times10^{-12}\,\mathrm{GeV}^{-1}$ at $28.54\,μ\mathrm{eV}$. These results consolidate the DALI approach and motivate a next-stage haloscope to explore a broader mass range with upgraded instrumentation.

hep-ex↗

arXiv2026

Constraints on Galactic Dark Photons from a DALI Prototype

An analysis of 36 hours of data from a DALI haloscope reveals no statistically significant excess attributable to dark-photon dark matter. We therefore set new constraints in the 6.88691--6.91792 GHz band, reaching a dark-photon-to-photon kinetic mixing strength of $χ\lesssim 6.8\times10^{-14}$ at $28.54 \, μ\mathrm{eV}$. To our knowledge, this result established the strongest laboratory-based exclusion limit in this frequency range.

hep-ex↗

arXiv2026

The DALI Haloscope: A Magnetized Phased Array Coupled to a Semi-Open Fabry--Pérot Resonator

DALI is an axion haloscope consisting of a magnetized phased array backed by a conducting mirror and coupled in the near field to a semi-open Fabry--Pérot resonator. The applied static magnetic field makes both the dielectric interfaces and the conducting mirror sensitive to axion-induced electromagnetic conversion. Each interface acts as a radiating surface, and the resulting fields are projected onto the mode collected by the resonator and delivered to the receiver. We derive the detected power in terms of the power available from the magnetized mirror, the coherent contribution of the dielectric interfaces, the transverse mode overlap, the loaded quality factor, and the receiver-coupling coefficient. This formulation separates two distinct enhancement mechanisms. The dielectric-interface emissions may add coherently, producing a dielectric boost, while the semi-open Fabry--Pérot resonator provides enhancement through resonant storage of the coupled electromagnetic field. These contributions depend differently on the dielectric thicknesses, spacings, and resonant mode, and should therefore be evaluated independently. The same assembly can operate between the limits of a coherently boosted dielectric haloscope and a mirror-sourced, resonantly enhanced Fabry--Pérot haloscope. This combined architecture offers a flexible approach to resonant axion searches at frequencies for which conventional closed microwave cavities become increasingly limited in conversion volume.

hep-ex↗

arXiv2026

Search for a solar-bound axion halo using the Global Network of Optical Magnetometers for Exotic physics searches

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 pseudo-magnetic 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 pseudo-magnetic field over the frequency range $\approx 0.05-20$ 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.

physics.atom-ph↗

arXiv2025

The search for dark matter axions from neutron stars in the inner parsecs of the Milky Way with AtLAST

The magnetospheres of neutron stars in the Galactic Center provide an exceptional environment to search for dark matter axions through their resonant conversion into photons. The combination of extreme magnetic fields and high dark matter density in this region creates ideal conditions for axion-photon conversion across the centimetre-to-submillimetre wavelength range. Detecting the cumulative emission from these neutron star populations demands a facility with unprecedented sensitivity, spatial resolution, and broad frequency coverage in the submillimetre domain, capabilities essential to explore a previously inaccessible region of axion parameter space.

astro-ph.IM↗

arXiv2024

DALI sensitivity to streaming axion dark matter

Dark matter substructures emerge naturally in a scenario in which the axion angular field acquires propagating degrees of freedom in a post-inflationary Universe. The DALI experiment is a new generation wavy dark matters interferometer currently in prototyping. Although DALI's main objective is to explore the virialized DM in our Galaxy, to a large degree in this article we explore the prospect for detection of fine grained streams made of axions that would enter the Solar System, as suggested by previous work. We find that DALI will have a sensitivity to encounters with these coherent objects that fully spans the window defined by the coupling strength to photons of representative axion models over a stacked bandwidth of two decades in mass.

hep-ph↗

arXiv2023

Gravitational focusing effects on streaming dark matter as a new detection concept

Cosmological simulations for cold dark matter (DM) indicate that a large number of streams might exist in our Galaxy. The present work incorporates gravitational focusing (GF) effects on streaming DM constituents by the Sun and the Earth preceding their encounter with Earth bound detectors. For streaming DM, the GF gives rise to spatiotemporal flux enhancements of orders of magnitude above the nominal DM density. Remarkably, due to Earth's rotation the derived flux enhancements appear as transient signals lasting about 10 seconds repeating daily for days or weeks. This work presents a novel opportunity for DM signal detection and identification, and the present simulation can be applied to any kind of invisible matter entering the solar system.

astro-ph.IM↗

arXiv2023

A Hunt for Magnetic Signatures of Hidden-Photon and Axion Dark Matter in the Wilderness

Earth can act as a transducer to convert ultralight bosonic dark matter (axions and hidden photons) into an oscillating magnetic field with a characteristic pattern across its surface. Here we describe the first results of a dedicated experiment, the Search for Non-Interacting Particles Experimental Hunt (SNIPE Hunt), that aims to detect such dark-matter-induced magnetic-field patterns by performing correlated measurements with a network of magnetometers in relatively quiet magnetic environments (in the wilderness far from human-generated magnetic noise). Our experiment constrains parameter space describing hidden-photon and axion dark matter with Compton frequencies in the 0.5-5.0 Hz range. Limits on the kinetic-mixing parameter for hidden-photon dark matter represent the best experimental bounds to date in this frequency range.

hep-ph↗

arXiv2023

Searching for axion streams with the echo method

The axion dark matter echo technique, proposed in Ref. [1], aims to search for axion dark matter by detecting the electromagnetic echo coming from stimulated decay of ambient axion dark matter interacting with a radio-microwave outgoing beam. In this work we consider deviations from the standard halo model (SHM) in the form of fine grained streams that are present in the solar system and use them as a target for the axion echo method, which demonstrates to be very sensitive to particular local axion dark matter phase space distributions. We show that the extremely small dispersion of the streams works in favor of the echo method performance, improving its sensitivity in the axion-photon coupling up to two orders of magnitude, with respect to the isotropic SHM. We also discuss the possibility of targeting high density dark matter hairs formed when fine grained streams focus by the inner Earth's gravitational field.

hep-ph↗

arXiv2005

Search for CPT Violation with the FOCUS Experiment and Measurement of $Λ_b$ lifetime in the decay $Λ_b\to J/ψΛ$ with the DØExperiment

We have performed a search for CPT violation in neutral charm meson oscillations using data from the FOCUS Experiment. While flavor mixing in the charm sector is predicted to be small by the Standard Model, it is still possible to investigate CPT violation through a study of the proper time dependence of a CPT asymmetry in right-sign decay rates for $D^0\to K^-π^+$ and $\d0b\to K^+π^-$. This asymmetry is related to the CPT violating complex parameter $ξ$ and the mixing parameters $x$ and $y$: $A_{CPT}\propto{\rm Re} ξy-{\rm Im} ξx$. Our 95% confidence level limit is $-0.0068<{\rm Re} ξy-{\rm Im} ξx<0.0234$. Within the framework of the Standard Model Extension incorporating general CPT violation, we also find 95% confidence level limits for the expressions involving coefficients of Lorentz violation. We present measurements of the \lb lifetime in the exclusive decay channel \lbdec with $J/ψ\to μ^+ μ^-$ and $Λ\to p π^-$, the $B^0$ lifetime in the decay \bddecks with $J/ψ\to mu^+ μ^-$ and $K^0_{S} \to π^+ π^-$, and the ratio of these lifetimes. The analysis is based on approximately 225 pb$^{-1}$ of data recorded with the DØdetector in $p bar{p}$ collisions at $\sqrt{s} =1.96$ TeV. The \lb lifetime is determined to be $τ(Λ^0_b) = 1.36 \pm 0.3 ps$, the $B^0$ lifetime $τ(Λ^0_b) = 1.43 \pm 0.12 ps$, and the ratio $\fr ac{τ(Λ_b)}{τ(B_d)}=0.95\pm0.22$. In contrast with previous measurements using semileptonic decays, this is the first determination of the \lb lifetime based on a fully reconstructed decay channel.

hep-ex↗