Dark Matter Detection Research Articles

What surfaces in the operation of noble liquids dark matter detectors

Though noble element dual-phase detectors have a long application history in dark matter searches, some uncertainties and differences in backgrounds persist. We compare effects caused by unextracted electrons on the liquid-gas interface in Xe and Ar dual-phase detectors with a large family of phenomena at the liquid helium surface. We pose that electron and ion accumulation on the liquid surface in detectors can lead to the formation of ordered surface states, charged liquid surface instabilities in an electric field, electrospraying, interactions with surface waves, and other effects. Not only delayed electron emission signals can be generated, but the extraction efficiency for electrons produced below the liquid surface can be altered by the presence of surface charges. Several factors lead to surface electron accumulation, and problems can become more severe with the increased detector size. We discuss possible experiments to reveal surface electron effects and design changes to alleviate electron accumulation. We conclude that studies of these effects are desirable before making final design decisions for the new multi-ton liquid Xe dark matter detector projects like DARWIN, XLZD, and large Ar dual-phase detectors.

Directional direct detection of light dark matter up-scattered by cosmic rays from direction of the Galactic center

Dark matter with MeV scale mass is difficult to detect with standard direct search detectors. However, they can be searched for by considering the up-scattering of kinetic energies by cosmic rays. Because the dark matter density is higher in the central region of the Galaxy, the up-scattered dark matter will arrive at Earth from the direction of the Galactic center. Once the dark matter is detected, we can expect to recognize this feature by directional direct detection experiments. In this study, we simulate the nuclear recoils of the up-scattered dark matter and quantitatively reveal that a large amount of this type of dark matter is arriving from the direction of the Galactic center. Also, we have shown that the characteristic signatures of the up-scattered dark matter can be verified with more than 5σ confidence levels for the assumed target atoms and future upgrades to directional detectors.

Validation of electrodeposited 241Am alpha-particle sources for use in liquified gas detectors at cryogenic temperatures

This paper describes a procedure for the validation of alpha-particle sources (exempt unsealed sources) to be used in experimental setups with liquefied gases at cryogenic temperatures (down to −196 °C) and high vacuum. These setups are of interest for the development and characterization of neutrino and dark matter detectors based on liquid argon, among others. Due to the high purity requirements, the sources have to withstand high vacuum and cryogenic temperatures for extended periods. The validation procedure has been applied to 241Am sources produced by electrodeposition.

Enhancing strontium clock atom interferometry using quantum optimal control

Strontium clock atom interferometry is a promising new technology, with multiple experiments under development around the world to explore its potential for dark matter and gravitational wave detection. In these detectors, large momentum transfer using sequences of many laser pulses is necessary, and thus high-fidelity pulses are important since small errors become magnified. Quantum optimal control (QOC) is a framework for developing control pulse waveforms that achieve high fidelity and are robust against experimental imperfections. Resonant single-photon transitions using the narrow clock transition of strontium involve significantly different quantum dynamics than more established atom interferometry methods based on far-detuned two-photon Raman or Bragg transitions, which leads to new opportunities and challenges when applying QOC. Here, we study in simulation QOC pulses for strontium clock interferometry and demonstrate their advantage over basic square pulses (primitive pulses) and composite pulses in terms of robustness against multiple noise channels. This could improve the scale of large momentum transfer in Sr clock interferometers, paving the way to achieving these scientific goals.

Suppression of accidental backgrounds with deep neural networks in the PandaX-II experiment

The PandaX dark matter detection project searches for dark matter particles using the technology of dual phase xenon time projection chamber. The low expected rate of the signal events makes the control of backgrounds crucial for the experiment success. In addition to reducing external and internal backgrounds during the construction and operation of the detector, special techniques are employed to suppress the background events during the data analysis. In this article, we demonstrate the use of deep neural networks (DNNs) for suppressing the accidental backgrounds, as an alternative to the boosted-decision-tree method used in previous analysis of PandaX-II. A new data preparation approach is proposed to enhance the stability of the machine learning algorithms to be run and ultimately the sensitivity of the final data analysis.

Tremaine-Gunn limit with mass-varying particles

General classical arguments on the time evolution of the phase-space density can be used to derive constraints on the mass of particle candidates for the cosmological dark matter (DM). The resulting Tremaine-Gunn limit is extremely useful in constraining particle DM models. In certain models, however, the DM particle mass varies appreciably over time. In this work, we generalize the phase-space limits on possible DM particle masses to these scenarios. We then examine the ensuing cosmological implications on the effective DM equation of state and indirect DM detection.

Different Detection Methods for Dark Matter

Dark matter has been proposed to fulfill the missing mass from Astro-observation. Many theories have been raised to explain dark matter, and weakly interacting massive particles (WIMPs) are one of them. In recent decades, dark matter detection sensitivity has improved significantly. However, solid evidence for their existence has not come yet. This paper outlines some methods for detecting dark matter, including direct detections, collider searches with the ATLAS detector at LHC, and collider searches with CEPC.

Lepton-flavoured scalar dark matter in Dark Minimal Flavour Violation

We study a simplified model of lepton-flavoured complex scalar dark matter set up in the Dark Minimal Flavour Violation framework. In this model the Standard Model is extended by a scalar dark matter flavour triplet and a charged fermionic mediator, through which dark matter couples to the right-handed charged leptons of the Standard Model. This interaction is parameterized by a new 3 × 3 coupling matrix λ. Consistent with the field content of the model, also the Standard Model’s approximate flavour symmetry is extended to include an additional global U(3) associated with the dark matter flavour triplet. In addition to the Standard Model Yukawa couplings, the new coupling matrix λ is assumed to constitute the only source that violates this extended symmetry. We analyse the parameter space of this model by investigating constraints from collider searches, lepton flavour violating decays, the observed dark matter relic density, and direct as well as indirect dark matter detection experiments. By performing a combined analysis of all constraints we find that restrictions from lepton flavour violating decays, the observed relic density and dark matter nucleon scattering are dominant. The combination of the latter two renders limits from collider searches irrelevant while indirect detection constraints are weak due to a p-wave suppression of the annihilation rate. We conclude that lepton-flavoured scalar dark matter has a rich phenomenology and is a viable dark matter candidate.

Characterization of two SiPM arrays from Hamamatsu and Onsemi for liquid argon detector

Silicon photomultiplier is considered a substitute for traditional photomultiplier tube in the next generation of dark matter and neutrino detectors, especially in noble gas detectors like liquid argon. For seeking more choices operating in a cryogenic environment, two SiPM array candidates from Hamamatsu and Onsemi were selected to verify their feasibility and effectiveness in liquid argon temperature. In this work, by inheriting the circuit DarkSide Collaboration designed earlier, we developed a cryogenic electronics read-out system that connects and works with 1-inch 4 × 4 SiPM arrays at 87 K. The amplifier’s power dissipation is around 10 μW/mm2. Furthermore, multiple significant characteristics of both types of SiPM arrays were measured at liquid argon temperature, such as the breakdown voltage, the dark count rate, the single photoelectron performance, the signal-to-noise ratio, and the correlated signal probability.

The Proposed Analytical Model and Detection Scenarios for Axion and Wimps

Contemporarily, the detection of dark matter is still an unsolved issue for modern physics. Among all the candidates of the dark matter models, the axion and Weakly interacting massive particles (WIMPs) are the most two appealing cases for realizing detection. On this basis, this paper investigates the analytical model construction of the axion and WIMPs based on the concepts of standard model. Subsequently, the detection mechanisms as well as the state-of-art facilities are demonstrated, respectively. Eventually, guideline for future detection and improvement scheme are proposed in order to find the dark matter mass region. Overall, these results shed light on future dark matter detection and model construction.

The neutrino floor: a data-driven analysis

We reconsider the discovery limit of multi-ton direct detection dark matter experiments in the light of recent measurements of the coherent elastic neutrino-nucleus scattering process. Assuming the cross section to be a parameter entirely determined by data, rather than using its Standard Model prediction, we use the COHERENT CsI and LAr data sets to determine WIMP discovery limits. Being based on a data-driven approach, the results are thus free from theoretical assumptions and fall within the WIMP mass regions where XENONnT and DARWIN have best expected sensitivities. We further determine the impact of subleading nuclear form factor and weak mixing angle uncertainties effects on WIMP discovery limits. We point out that these effects, albeit small, should be taken into account. Moreover, to quantify the impact of new physics effects in the neutrino background, we revisit WIMP discovery limits assuming light vector and scalar mediators as well as neutrino magnetic moments/transitions. We stress that the presence of new interactions in the neutrino sector, in general, tend to worsen the WIMP discovery limit.

Search for leptophilic dark matter at the LHeC

The Large Hadron electron Collider (LHeC) has been designed to push the field of deep inelastic scattering to the high energy and intensity frontier using an intense electron beam with a proton beam from the High Luminosity–Large Hadron Collider. However, LHeC is also a great laboratory for new physics. In this work, we propose a search for dark matter that couples with leptons. This may yield and signals that can be potentially observed through simple missing-energy cuts that suppress the Standard Model background. Considering direct dark matter detection and LHC constraints, we show that LHeC offers a complementary probe for a weak scale dark matter fermion for masses up to 350 GeV, which reproduces the correct relic density, and has interesting implications for lepton flavor violation.

Weakly interacting massive particle cross section limits from LOFAR observations of dwarf spheroidal galaxies

Context. Weakly interacting massive particles (WIMPs) can self-annihilate, thus providing us with a way to indirectly detect dark matter (DM). Dwarf spheroidal (dSph) galaxies are excellent places to search for annihilation signals because they are rich in DM and background emission is low. If O(0.1–10 μG) magnetic fields in dSph galaxies exist, the particles produced in DM annihilation emit synchrotron radiation in the radio band. Aims. We used the non-detection of 150 MHz radio continuum emission from dSph galaxies with the LOw Frequency ARray (LOFAR) to derive constraints on the annihilation cross section of WIMPs in electron–positron pairs. Our main underlying assumption is that the transport of the cosmic rays can be described by the diffusion approximation, which necessitates the existence of magnetic fields. Methods. We used observations of six dSph galaxies in the LOFAR Two-metre Sky Survey (LoTSS). The data were reimaged, and a radial profile was generated for each galaxy. We also used stacking to increase the sensitivity. In order to derive upper limits on the WIMP cross section, we injected fake Gaussian sources into the data, which were then detected with 2σ significance in the radial profile. These sources represent the lowest emission we would have been able to detect. Results. We present limits from the observations of individual galaxies as well as from stacking. We explored the uncertainty due to the choice of diffusion and magnetic field parameters by constructing three different model scenarios: optimistic (OPT), intermediate (INT), and pessimistic (PES). Assuming monochromatic annihilation into electron–positron pairs, the limits from the INT scenario exclude thermal WIMPs (⟨σv⟩≈2.2 × 10−26 cm3 s−1) below 20 GeV, and the limits from the OPT scenario even exclude thermal WIMPs below 70 GeV. The INT limits can compete with limits set by Fermi-LAT using γ-ray observations of multiple dwarf galaxies, and they are especially strong for low WIMP masses.

Directional detection of light dark matter in superconductors

Superconducting detectors have been proposed as outstanding targets for the direct detection of light dark matter scattering at masses as low as a keV. We study the prospects for directional detection of dark matter in isotropic superconducting targets from the angular distribution of excitations produced in the material. We find that dark matter scattering produces initial excitations with an anisotropic distribution, and further show that this directional information can be preserved as the initial excitations relax. Our results demonstrate that directional detection is possible for a wide range of dark matter masses, and they pave the way for light dark matter discovery with bulk superconducting targets.

W-boson mass anomaly and vacuum structure in vector dark matter model with a singlet scalar mediator

Motivated by the deviation of the [Formula: see text]-boson mass reported by the CDF collaboration, we study an extension of the Standard Model (SM) including a vector dark matter (VDM) candidate and a scalar mediator. In the model, the one-loop corrections induced by the new scalar shift the [Formula: see text]-boson mass. We identify the parameter space of the model consistent with dark matter (DM) relic abundance, [Formula: see text]-mass boson anomaly, invisible Higgs decay at LHC, and direct detection of DM. It is shown that the [Formula: see text]-mass anomaly can be explained for the large part of parameter space of VDM mass and scalar mediator mass between 100[Formula: see text]GeV and 124[Formula: see text]GeV by the model. We also investigate the renormalization group equations (RGEs) at one-loop order for the model. We show that the contribution of new scalar mediator to RGE guarantees positivity and vacuum stability of SM Higgs up to Planck scale.

Halo-independent dark matter electron scattering analysis with in-medium effects

Dark matter (DM)-electron scattering is a prime target of a number of direct DM detection experiments and constitutes a promising avenue for exploring interactions of DM in the sub-GeV mass-range, challenging to probe with nuclear recoils. We extend the recently proposed halo-independent analysis method for DM-electron scattering, which allows to infer the local DM halo properties without any additional assumptions about them, to include in-medium effects through dielectric functions of the target material. We show that in-medium effects could significantly affect halo-independent analysis response functions for germanium and silicon and thus are essential for proper inference of local DM halo characteristics from direct DM detection data.

Celestial objects as strongly-interacting nonannihilating dark matter detectors

Nonannihilating dark matter particles, owing to their interactions with ordinary baryonic matter, can efficiently accumulate inside celestial objects. For heavy mass, they gravitate toward the core of the celestial objects, thermalize in a small core region, and eventually form tiny black holes via core collapse, resulting destruction of the host objects. We demonstrate that the existence of a variety of celestial objects provides stringent constraints on strongly interacting heavy dark matter, a blind spot for the terrestrial dark matter detectors as well as for the cosmological probes. Celestial objects with larger sizes and lower core temperatures, such as Jupiter, are the most optimal detectors to probe the strongly interacting heavy nonannihilating dark matter.

Enhanced prospects for direct detection of inelastic dark matter from a non-galactic diffuse component

In some scenarios, the dark matter particle predominantly scatters inelastically with the target, producing a heavier neutral particle in the final state. In this class of scenarios, the reach in parameter space of direct detection experiments is limited by the velocity of the dark matter particle, usually taken as the escape velocity from the Milky Way. On the other hand, it has been argued that a fraction of the dark matter particles in the Solar System could be bound to the envelope of the Local Group or to the Virgo Supercluster, and not to our Galaxy, and therefore could carry velocities larger than the escape velocity from the Milky Way. In this paper we estimate the enhancement in sensitivity of current direct detection experiments to inelastic dark matter scatterings with nucleons or electrons due to the non-galactic diffuse components, and we discuss the implications for some well motivated models.

Energy resolution of the LZ detector for high-energy electronic recoils

The LUX-ZEPLIN (LZ) detector is a dual-phase liquid xenon time projection chamber (TPC) installed at the Sanford Underground Research Facility (Lead, South Dakota) at a depth of 1478 meters. Although the main objective of LZ is the direct detection of dark matter, its low background environment allows for the search of other rare processes, such as the neutrinoless double beta decay of xenon isotopes 134Xe and 136Xe with the respective Q-values of 826 keV and 2458 keV. The sensitivity of the detector to these decays is directly determined by the energy resolution, which, in turn, is degraded by non-uniformities in detector response. In this work, we present a novel method to correct, in the data, the non-uniformity of the light collected by an array of photosensors in a scintillation detector. This method is based on the knowledge of the light response functions of individual photosensors. With these techniques, we report, at a very early phase of the detector operations, a state-of-the-art energy resolution (σ/μ) of (0.67 ± 0.01)% at 2614 keV for the fiducial volume of 5.6 tonnes of liquid xenon.

Measurement of the Compton scattering in germanium with a p-type point-contact germanium detector for dark matter detection

Low-energy background through Compton scattering from the ambient γ rays can be contaminated in direct dark matter search experiments. In this paper, we report comparable measurements on low-energy spectra via Compton scattering from several γ-ray sources with a p-type point-contact germanium detector. The spectra between 500 eV and 18 keV have been measured and analyzed. Moreover, the features of the electron binding effect, particularly at the edges of the K- and L-shells in the germanium atom, were observed with different gamma sources and were consistent with the models in the Geant4 simulation. An empirical background model is proposed that provides insights into understanding the low-energy background in germanium for direct dark matter experiments.