Dark Matter Detection Research Articles

The data acquisition system of the LZ dark matter detector: FADR

The Data Acquisition System (DAQ) for the LUX-ZEPLIN (LZ) dark matter detector is described. The signals from 745 PMTs, distributed across three subsystems, are sampled with 100-MHz 32-channel digitizers (DDC-32s). A basic waveform analysis is carried out on the on-board Field Programmable Gate Arrays (FPGAs) to extract information about the observed scintillation and electroluminescence signals. This information is used to determine if the digitized waveforms should be preserved for offline analysis.The system is designed around the Kintex-7 FPGA. In addition to digitizing the PMT signals and providing basic event selection in real time, the flexibility provided by the use of FPGAs allows us to monitor the performance of the detector and the DAQ in parallel to normal data acquisition.The hardware and software/firmware of this FPGA-based Architecture for Data acquisition and Realtime monitoring (FADR) are discussed and performance measurements are described.

Exploring hidden signal: Fine-tuning ResNet-50 for dark matter detection

In pursuit of detecting dark matter signals, the Large Hadron Collider (LHC) at CERN has conducted proton-proton collisions to probe for these elusive particles, whose existence has been supported by astronomical observations. Despite extensive efforts by the CMS and ATLAS experiments, the direct detection of dark matter signals remains elusive. The current approaches employed for analyzing dark matter signatures utilize the cut-and-count method based on conventional techniques. This study introduces an alternative method for exploring dark matter signatures by utilizing fine-tuning of pre-trained models, such as ResNet-50, on 2D histograms generated from a combination of signal + background samples and background-only samples. By utilizing various signal-to-background ratios as benchmarks, an accuracy of about 90% for a signal-to-background ratio of 0.008 is achieved. This approach not only offers a more refined search for dark matter signals but also presents an efficient and effective means of analysis using machine learning techniques.

Dark sink enhances the direct detection of freeze-in dark matter

We describe a simple dark sector structure which, if present, has implications for the direct detection of dark matter (DM); . A dark sink transports energy density from the DM into light dark-sector states that do not appreciably contribute to the DM density. As an example, we consider a light, neutral fermion ψ which interacts solely with DM χ via the exchange of a heavy scalar Φ. We illustrate the impact of a dark sink by adding one to a DM freeze-in model in which χ couples to a light dark photon γ′ which kinetically mixes with the Standard Model (SM) photon. This freeze-in model (absent the sink) is itself a benchmark for ongoing experiments. In some cases, the literature for this benchmark has contained errors; we correct the predictions and provide them as a public code. We then analyze how the dark sink modifies this benchmark, solving coupled Boltzmann equations for the dark-sector energy density and DM yield. We check the contribution of the dark sink ψ’s to dark radiation; consistency with existing data limits the maximum attainable cross section. For DM with a mass between MeV−O(10 GeV), adding the dark sink can increase predictions for the direct detection cross section all the way up to the current limits. Published by the American Physical Society 2024

Deepest sensitivity to wavelike dark photon dark matter with superconducting radio frequency cavities

Wavelike, bosonic dark matter candidates like axions and dark photons can be detected using microwave cavities known as haloscopes. Traditionally, haloscopes consist of tunable copper cavities operating in the TM010 mode, but ohmic losses have limited their performance. In contrast, superconducting radio frequency (SRF) cavities can achieve quality factors of ∼1010, perhaps 5 orders of magnitude better than copper cavities, leading to more sensitive dark matter detectors. In this paper, we first derive that the scan rate of a haloscope experiment is proportional to the loaded quality factor QL, even if the cavity bandwidth is much narrower than the dark matter halo line shape. We then present a proof-of-concept search for dark photon dark matter using a nontunable ultrahigh-quality SRF cavity. We exclude dark photon dark matter with kinetic mixing strengths of χ>1.5×10−16 for a dark photon mass of mA′=5.35 μeV, achieving the deepest exclusion to wavelike dark photons by almost an order of magnitude. Published by the American Physical Society 2024

Investigating higgsino dark matter in the semi-constrained NMSSM* *Supported by the National Natural Science Foundation of China (12275066, 11605123)

In this study, we explored the characteristics of higgsino-dominated dark matter (DM) within the semi-constrained Next-to-Minimal Supersymmetric Standard Model (scNMSSM), covering a mass range from hundreds of GeV to several TeV. We carefully analyzed the parameter space under existing theoretical and experimental constraints to confirm the viability of higgsino-dominated lightest supersymmetric particles (LSPs) with masses between 100 GeV and 4 TeV. Our study examined various DM annihilation mechanisms, emphasizing the significant role of coannihilation with the next-to-lightest supersymmetric particle (NLSP), which includes other higgsino-dominated particles such as and . We categorize the annihilation processes into three main classes: coannihilation, Higgs funnel annihilation, and coannihilation. Each class combines interactions with . Our results indicate that achieving the correct relic density in heavier higgsino LSPs requires a combination of coannihilation and Higgs funnel mechanisms. We also assessed the potential of future experiments, such as XENONnT, LUX-ZEPLIN (LZ), PandaX-xT, and the Cherenkov Telescope Array (CTA), to probe these DM scenarios through direct and indirect detections. In particular, future spin-independent DM detections may cover all samples with the correct DM relic density for GeV. Furthermore, future colliders such as the International Linear Collider (ILC) and Compact Linear Collider (CLIC) are expected to exceed the detection capabilities of current hadron colliders, especially for higher mass NLSPs. Notably, CLIC, which will operate at 3000 GeV, is anticipated to enable thorough investigation of all samples with insufficient DM relic density for GeV.

Constraints on Ultraheavy Dark Matter Properties from Dwarf Spheroidal Galaxies with LHAASO Observations.

In this Letter we try to search for signals generated by ultraheavy dark matter at the Large High Altitude Air Shower Observatory (LHAASO) data. We look for possible γ rays by dark matter annihilation or decay from 16 dwarf spheroidal galaxies in the field of view of the LHAASO. Dwarf spheroidal galaxies are among the most promising targets for indirect detection of dark matter that have low fluxes of astrophysical γ-ray background while having large amount of dark matter. By analyzing more than 700days of observational data at LHAASO, no significant dark matter signal from 1TeV to 1EeV is detected. Accordingly we derive the most stringent constraints on the ultraheavy dark matter annihilation cross section up to EeV. The constraints on the lifetime of dark matter in decay mode are also derived.

Optomechanical dark matter instrument for direct detection

We propose the Optomechanical Dark-matter Instrument (ODIN), based on a new method for the direct detection of low-mass dark matter. We consider dark matter interacting with superfluid helium in an optomechanical cavity. Using an effective field theory, we calculate the rate at which dark matter scatters off phonons in a highly populated, driven acoustic mode of the cavity. This scattering process deposits a phonon into a second acoustic mode in its ground state. The deposited phonon (μeV range) is then converted to a photon (eV range) via an optomechanical interaction with a pump laser. This photon can be efficiently detected, providing a means to sensitively probe keV scale dark matter. We provide realistic estimates of the backgrounds and discuss the technical challenges associated with such an experiment. We calculate projected limits on dark matter–nucleon interactions for dark matter masses ranging from 0.5 to 300 keV and estimate that a future device could probe cross sections as low as O(10−32) cm2. Published by the American Physical Society 2024

Radiative corrections to aid the direct detection of the Higgsino-like neutralino dark matter: Spin-independent interactions

The lightest neutralino (χ˜10) is a good dark matter (DM) candidate in the R-parity conserving minimal supersymmetric Standard Model. In this work, we consider the light Higgsino-like neutralino as the lightest stable particle, thanks to a rather small Higgsino mass parameter μ. We then estimate the prominent radiative corrections to the neutralino-neutralino-Higgs boson vertices. We show that for Higgsino-like χ˜10, these corrections can significantly influence the spin-independent direct detection cross section, even contributing close to 100% in certain regions of the parameter space. These corrections, therefore, play an important role in deducing constraints on the mass of the Higgsino-like lightest neutralino DM, and thus the μ parameter. Published by the American Physical Society 2024

First measurement of Gallium Arsenide as a low-temperature calorimeter

In the quest for direct dark matter detection, innovative approaches to lower the detection threshold and explore the sub-GeV mass range, have gained high relevance in the last decade. This study presents the pioneering use of Gallium Arsenide (GaAs) as a low-temperature calorimeter for probing dark matter-electron interactions within the DAREDEVIL (DARk-mattEr DEVIces for Low energy detection) project. Our experimental setup features a GaAs crystal at an ultralow temperature of 15 mK, coupled with a Neutron Transmutation Doped Germanium (NTD-Ge) thermal sensor for precise energy estimation. This configuration is the first step towards detecting single electrons scattered by dark matter particles within the GaAs crystal, to improve the sensitivity to low-mass dark matter candidates significantly. Taking advantage of the production of optical phonons in polar materials such as GaAs gives the possibility to study the scattering of sub-MeV dark matter. This paper presents a detailed analysis of the detector’s response, using a calibration spectrum using α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} particles and X-ray events. While the results do not meet the ambitious eV scale threshold yet, they establish a solid benchmark for assessing the detector’s current performance and sensitivity. This work not only highlights the detector’s potential but also sets the stage for future enhancements aimed at achieving the eV threshold, underscoring the promising direction of this detector technology. These findings demonstrate the feasibility of using GaAs as a cryogenic calorimeter and hence open new avenues for investigating the elusive nature of dark matter through innovative direct detection techniques.

Overview of dark matter detection

Dark matter is a perplexing and hard-to-find form of matter that governs the gravitational dynamics of the universe. This paper presents an overview of the existing comprehension of dark matter discovery, with emphasis on its theoretical structure, detection techniques, and future possibilities. The standard model of particle physics, even though effective in detailing recognized particles and forces, falls short in describing dark matter. Various theories and models, such as the Cold Dark Matter and Weakly Interacting Massive Particles models, have been proposed to explain the character of dark matter. Direct and indirect detection methods, including underground experiments, cosmic microwave background studies and collider experiments, are used to find dark matter. Despite extensive efforts, the direct detection of dark matter particles remains elusive. The detection of dark matter poses various challenges such as weak interactions and the requirement for highly sensitive detectors. Progress in dark matter detection will depend on advancements in detector technology, addressing open questions, and theoretical developments, which will offer insights into the fundamental laws of nature and the structure of the universe.

Probing black holes in a dark matter spike of M87 using quasinormal modes

Dark matter density can be significantly enhanced by the supermassive black hole at the galactic center, leading to a structure called dark matter spike. Dark matter spike may change the spacetime properties of black holes that constitute deviations from GR black holes. Based on these interesting background, we construct a set of solutions of black holes in a dark matter spike under the Newtonian approximation and full relativity. Combining the mass model of M87, we study the quasinormal modes of black holes in the scalar field and axial gravitational perturbation, then compared them with Schwarzschild black hole. Besides, the impacts of dark matter on the quasinormal mode of black holes have been studied in depth. In particular, in the axial gravitational perturbation, our results show that the impacts of dark matter spike on the quasinormal mode of black holes can reach up to 10-4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{-4}$$\\end{document}. These new features from quasinormal mode of black holes under the Newtonian approximation and full relativity may provide some help for the establishment of the final dark matter model, and provide a new thought for the indirect detection of dark matter.

Model for bubble nucleation efficiency of low-energy nuclear recoils in bubble chambers for dark matter detection

Bubble chambers are promising technologies for detecting low-energy nuclear recoils from the elastic scattering of dark matter particle candidates. Bubble nucleation occurs when the energy deposition exceeds a specific threshold defined traditionally by the “heat-spike” Seitz threshold. In this paper, we report on a physical model that can account for observed discrepancies between the current Seitz model and the measured nucleation efficiency of low-energy nuclear recoils, which is necessary for interpreting dark matter signals. In our work, we combine molecular dynamics and Monte Carlo simulations together with the Lindhard model to predict bubble nucleation efficiency and energy thresholds for C3F8, CF3I, and xenon with enhanced accuracy over the Seitz model when compared to existing experimental data. We use our model to determine the effect on cross-section limits for spin-dependent and spin-independent interactions and compare it to the current PICO dark matter experiment. Our technique can also be applied to estimate the efficiency of future target fluids where no experimental data are available. As an example, we predict the nucleation efficiency, the energy threshold, and the cross-section limits in the spin-independent channel for the Scintillating Bubble Chamber experiment filled with superheated liquid argon. Published by the American Physical Society 2024

Deep probabilistic direction prediction in 3D with applications to directional dark matter detectors

We present the first method to probabilistically predict 3D direction in a deep neural network model. The probabilistic predictions are modeled as a heteroscedastic von Mises-Fisher distribution on the sphere S2 , giving a simple way to quantify aleatoric uncertainty. This approach generalizes the cosine distance loss which is a special case of our loss function when the uncertainty is assumed to be uniform across samples. We develop approximations required to make the likelihood function and gradient calculations stable. The method is applied to the task of predicting the 3D directions of electrons, the most complex signal in a class of experimental particle physics detectors designed to demonstrate the particle nature of dark matter and study solar neutrinos. Using simulated Monte Carlo data, the initial direction of recoiling electrons is inferred from their tortuous trajectories, as captured by the 3D detectors. For 40 keV electrons in a 70% He 30% CO2 gas mixture at STP, the new approach achieves a mean cosine distance of 0.104 (26∘) compared to 0.556 (64∘) achieved by a non-machine learning algorithm. We show that the model is well-calibrated and accuracy can be increased further by removing samples with high predicted uncertainty. This advancement in probabilistic 3D directional learning could increase the sensitivity of directional dark matter detectors.

Probing earth-bound dark matter with nuclear reactors

Strongly-interacting dark matter can be accumulated in large quantities inside the Earth, and for dark matter particles in a few GeV mass range, it can exist in large quantities near the Earth’s surface. We investigate the constraints imposed on such dark matter properties by its upscattering by fast neutrons in nuclear reactors with subsequent scattering in nearby well-shielded dark matter detectors, schemes which are already used for searches of the coherent reactor neutrino scattering. We find that the existing experiments cover new parameter space on the spin-dependent interaction between dark matter and the nucleon. Similar experiments performed with research reactors, and lesser amount of shielding, may provide additional sensitivity to strongly-interacting dark matter.

Measurement of the sodium and iodine scintillation quenching factors across multiple NaI(Tl) detectors to identify systematics

The amount of light produced by nuclear recoils in scintillating targets is strongly quenched compared to that produced by electrons. A precise understanding of the quenching factor is particularly interesting for weakly interacting massive particles (WIMP) searches and coherent elastic neutrino-nucleus scattering (CEνNS) measurements since both rely on nuclear recoils, whereas energy calibrations are more readily accessible from electron recoils. There is a wide variation among the current measurements of the quenching factor in sodium iodide (NaI) crystals, especially below 10 keV, the energy region of interest for dark matter and CEνNS studies. A better understanding of the quenching factor in NaI(Tl) is of particular interest for resolving the decades-old puzzle in the field of dark matter between the null results of most WIMP searches and the claim for dark matter detection by the DAMA/LIBRA collaboration. In this work, we measured sodium and iodine quenching factors for five small NaI(Tl) crystals grown with similar thallium concentrations and growth procedures. Unlike previous experiments, multiple crystals were tested, with measurements made in the same experimental setup to control systematic effects. The quenching factors agree in all crystals we investigated, and both sodium and iodine quenching factors are smaller than those reported by DAMA/LIBRA. The dominant systematic effect was due to the electron equivalent energy calibration originating from the nonproportional behavior of the NaI(Tl) light yield at lower energies, potentially the cause for the discrepancies among the previous measurements. Published by the American Physical Society 2024

Quantum Enhancement in Dark Matter Detection with Quantum Computation.

We propose a novel method to significantly enhance the signal rate in qubit-based dark matter detection experiments with the help of quantum interference. Various quantum sensors possess ideal properties for detecting wavelike dark matter, and qubits, commonly employed in quantum computers, are excellent candidates for dark matter detectors. We demonstrate that, by designing an appropriate quantum circuit to manipulate the qubits, the signal rate scales proportionally to n_{q}^{2}, with n_{q} being the number of sensor qubits, rather than linearly with n_{q}. Consequently, in the dark matter detection with a substantial number of sensor qubits, a significant increase in the signal rate can be expected. We provide a specific example of a quantum circuit that achieves this enhancement by coherently combining the phase evolution in each individual qubit due to its interaction with dark matter. We also demonstrate that the circuit is fault tolerant to dephasing noises, a critical quantum noise source in quantum computers. The enhancement mechanism proposed here is applicable to various modalities for quantum computers, provided that the quantum operations relevant to enhancing the dark matter signal can be applied to these devices.

Higgs portal dark matter freeze-in at stronger coupling: observational benchmarks

We study freeze-in production of Higgs portal dark matter (DM) at temperatures far below the dark matter mass. The temperature of the Standard Model (SM) thermal bath may have never been high such that dark matter production via thermal emission has been Boltzmann-suppressed. This allows for a significant coupling between the Higgs field and DM, which is being probed by the direct DM detection experiments and invisible Higgs decay searches at the LHC. We delineate the corresponding parameter space in the Higgs portal framework with dark matter of spin 0, 1/2 and 1.

Sensitivity to sub-GeV dark matter from cosmic-ray scattering with very-high-energy gamma-ray observatories

Huge efforts have been deployed to detect dark matter (DM) in the GeV-TeV mass range involving various detection techniques, and led to strong constraints in the available parameter space. We compute here the sensitivity to sub-GeV DM that can be probed from the inevitable cosmic-ray scattering onto DM particles populating the Milky Way halo. Inelastic scattering of energetic cosmic rays off DM would produce high-energy gamma rays in the final state, providing a new avenue to probe the poorly-constrained so far sub-GeV dark matter mass range. In this work we derivesensitivity forecasts for the inelastic cosmic-ray proton-DM cross section for current and future very-high-energy gamma-ray observatories such as H.E.S.S., LHAASO, CTA and SWGO in the 100 eV to 100 MeV mass range. These inelastic cross section constraints are converted to the elastic proton-DM cross sectionto highlight further complementarity with cosmological, collider and direct detection searches.The sensitivity computed at 95% confidence level on the elastic cross section reaches ∼2 × 10-32 cm2 for a 100 keV DM mass for H.E.S.S.-like and ∼7 × 10-34 cm2 for a ∼1 keV DM mass for LHAASO. The sensitivity prospects for CTA and a strawman SWGO model reach ∼6 × 10-34 cm2 and ∼4 × 10-35 cm2, for DM masses of 10 keV and 1 keV, respectively. The sensitivity reach of the gamma-ray observatories considered here enables to probe an uncharted region of the DM mass-cross section parameter space.

Radon removal commissioning of the PandaX-4T cryogenic distillation system

The PandaX-4T distillation system, designed for the removal of krypton and radon from xenon, is evaluated for its radon removal efficiency using a 222Rn source during the online distillation process. The PandaX-4T dark matter detector is employed to monitor the temporal evolution of radon activity. To determine the radon reduction factor, the experimental data of radon atoms introduced into and bypassed the distillation system is compared. The results indicate that the PandaX-4T distillation system achieves a radon reduction factor exceeding 190 at the flow rate of 10 slpm and the reflux ratio of 1.44. Gas-only online distillation process of a flow rate of 20 slpm is also conducted without observing significant reduction of radon levels in the detector. This observation suggests that the migration flow of radon atoms from the liquid phase to the gas phase is limited, and the flow rate of gas circulation and duration of the process are insignificant compared to the total xenon mass of 5.6 tons in the detector. This study provides the experimental data to support the efficient removal of radon at ∼Bq level using the PandaX-4T distillation system, which is the prerequisite of the radon background control in the detector. The further operation with higher flow rate will be applied for the upcoming science run in PandaX-4T.

Earth-catalyzed detection of magnetic inelastic dark matter with photons in large underground detectors

Inelastic dark matter with moderate splittings, O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(few to 150) keV, can upscatter to an excited state in the Earth, with the excited state subsequently decaying, leaving a distinctive monoenergetic photon signal in large underground detectors. The photon signal can exhibit sidereal-daily modulation, providing excellent separation from backgrounds. Using a detailed numerical simulation, we examine this process as a search strategy for magnetic inelastic dark matter with the dark matter mass near the weak scale, where the upscatter to the excited state and decay proceed through the same magnetic dipole transition operator. At lower inelastic splittings, the scattering is dominated by moderate mass elements in the Earth with high spin, especially 27Al, while at larger splittings, 56Fe becomes the dominant target. We show that the proposed large volume gaseous detector CYGNUS will have excellent sensitivity to this signal. Xenon detectors also provide excellent sensitivity through the inelastic nuclear recoil signal, and if a future signal is seen, we show that the synergy among both types of detection can provide strong evidence for magnetic inelastic dark matter. In the course we have calculated nuclear response functions for elements relevant for scattering in the Earth, which are publicly available on GitHub.