Dark Matter Direct Detection Research Articles

The impact of the Large Magellanic Cloud on dark matter direct detection signals

We study the effect of the Large Magellanic Cloud (LMC) on the dark matter (DM) distribution in the Solar neighborhood, utilizing the Auriga magneto-hydrodynamical simulations of Milky Way (MW) analogues that have an LMC-like system. We extract the local DM velocity distribution at different times during the orbit of the LMC around the MW in the simulations. As found in previous idealized simulations of the MW-LMC system, we find that the DM particles in the Solar neighborhood originating from the LMC analogue dominate the high speed tail of the local DM speed distribution. Furthermore, the native DM particles of the MW in the Solar region are boosted to higher speeds as a result of a response to the LMC's motion.We simulate the signals expected in near future xenon, germanium, and silicon direct detection experiments, considering DM interactions with target nuclei or electrons. We find that the presence of the LMC causes a considerable shift in the expected direct detection exclusion limits towards smaller cross sections and DM masses, with the effect being more prominent for low mass DM. Hence, our study shows, for the first time, that the LMC's influence on the local DM distribution is significant even in fully cosmological MW analogues.

Direct detection of finite-size dark matter via electron recoil

In direct dark matter (DM) detection via scattering off the electrons, the momentum transfer plays a crucial role. Previous work showed that for self-interacting DM, if the DM particle has a size (the so-called puffy DM), the radius effect could dominate the momentum transfer and become another source of velocity dependence for self-scattering cross-section. In this work, we investigate the direct detection of puffy DM particles with different radii through electron recoil. We find that comparing with the available experimental exclusion limits dominated by the mediator effect for XENON10, XENON100 and XENON1T, the constraints on the puffy DM-electron scattering cross-section become much weaker for large radius DM particles. For small-radius DM particles, the constraints remain similar to the point-like DM case.

Simulation and background characterisation of the SABRE South experiment

SABRE (Sodium iodide with Active Background REjection) is a direct detection dark matter experiment based on arrays of radio-pure NaI(Tl) crystals. The experiment aims at achieving an ultra-low background rate and its primary goal is to confirm or refute the results from the DAMA/LIBRA experiment. The SABRE Proof-of-Principle phase was carried out in 2020–2021 at the Gran Sasso National Laboratory (LNGS), in Italy. The next phase consists of two full-scale experiments: SABRE South at the Stawell Underground Physics Laboratory, in Australia, and SABRE North at LNGS. This paper focuses on SABRE South and presents a detailed simulation of the detector, which is used to characterise the background for dark matter searches including DAMA/LIBRA-like modulation. We estimate an overall background of 0.72 cpd/kg/hbox {keV}_{hbox {{ee}}} in the energy range 1–6 hbox {keV}_{hbox {{ee}}} primarily due to radioactive contamination in the crystals. Given this level of background and considering that the SABRE South has a target mass of 50 kg, we expect to exclude (confirm) DAMA/LIBRA modulation at 4~(5)sigma within 2.5 years of data taking.

Direct detection of electroweak dark matter

TeV-scale dark matter is well motivated by notions of naturalness as the new physics threshold is expected to emerge in the TeV regime. We generalise the Standard Model by including an arbitrary SU(2) multiplet of dark matter particles in non-chiral representation. The pseudo-real representations can be viable DM candidates if one considers a higher-dimensional operator which induces mass-splitting, and avoids the tree-level inelastic scattering through Z-boson exchange. These effective operators give rise to sizable contributions from Higgs mediated dark matter interactions with quarks and gluons. A linear combination of the effective couplings named lambda is identified as the critical parameter in determining the magnitude of the cross-section. When lambda is smaller than the critical value, the theory behaves similar to the known renormalisable model, and the scattering rate stays below the current experimental reach. Nevertheless, above the criticality, the contribution from the higher-dimensional operators significantly changes the phenomenology. The scattering amplitude of pseudo-real models will be coherently enhanced, so that it would be possible for next generation large-exposure experiments to fully probe these multiplets. We studied the parameter space of the theory, taking into account both indirect astrophysical and direct search constraints. It is inferred that multi-TeV mass scale remains a viable region, quite promising for forthcoming dark matter experiments.

High-resolution Chemical Abundances of the Nyx Stream

Nyx is a nearby, prograde, and high-eccentricity stellar stream physically contained in the thick disk, but its origin is unknown. Nyx could be the remnant of a disrupted dwarf galaxy, in which case the associated dark matter substructure could affect terrestrial dark matter direct-detection experiments. Alternatively, Nyx could be a signature of the Milky Way’s disk formation and evolution. To determine the origin of Nyx, we obtained high-resolution spectroscopy of 34 Nyx stars using Keck/HIRES and Magellan/MIKE. A differential chemical abundance analysis shows that most Nyx stars reside in a metal-rich ([Fe/H] > −1) high-α component that is chemically indistinguishable from the thick disk. This rules out the originally suggested scenario that Nyx is the remnant of a single massive dwarf galaxy merger. However, we also identify 5 substantially more metal-poor stars ([Fe/H] ∼ −2.0) whose chemical abundances are similar to those of the metal-weak thick disk. It remains unclear how stars that are chemically identical to the thick disk can be on such prograde, high-eccentricity orbits. We suggest two most likely scenarios: that Nyx is the result of an early minor dwarf galaxy merger, or that it is a record of the early spin-up of the Milky Way disk—although neither perfectly reproduces the chemodynamic observations. The most likely formation scenarios suggest that future spectroscopic surveys should find Nyx-like structures outside of the solar neighborhood.

Cryogenic phonon-detector model with solid argon for detecting dark matter* *This work is supported by the National Key Research and Development Program of China (2017YFA0402203) and the National Natural Science Foundation of China (12075161)

Over the past few years, phonon detectors have emerged as a prevailing technology for detecting low-mass dark matter due to their low thresholds and high resolution. These detectors, which employ either dual-phase detectors combining phonon-light or phonon-electron interactions, have significantly advanced direct dark matter detection efforts. Argon, as a low-background and high-reserve detection medium, has also played a crucial role in this field. Both liquid-argon single-phase detectors and gas-liquid two-phase time projection chambers (TPCs) have contributed substantially to the direct detection of high-mass dark matter. By integrating these distinct detector types, the upper limits of the corresponding mass cross-section in dark matter detection can be lowered. We propose a phonon detector utilizing solid argon as the absorber, which combines the advantages of both aforementioned detector types. However, due to the requirement for an ultra-low temperature environment in the tens of millikelvin (mK) range, experimental investigations of solid argon phonon detector performance are currently constrained by technical limitations. Therefore, the performance analysis of the solid argon phonon detector presented in this study is only based on sapphire phonon detectors. Although there may be discrepancies between this approximation and the actual performance, the intrinsic characteristics of phonon detectors permit a qualitative evaluation of the solid argon phonon detector's potential capabilities.

Probing light DM via the Migdal effect with spherical proportional counter* *Supported by the National Natural Science Foundation of China (12275134, 12275232, 12335005, 12147228), and the Natural Science Foundation of Shandong Province, China (ZR2018QA007)

Owing to its low electronic noise and flexible target materials, the Spherical Proportional Counter (SPC) with a single electron detection threshold can be utilized to search for sub-GeV dark matter (DM). In this study, we investigate the prospects for light DM direct detection via the DM-nucleus Migdal effect in the DARKSPHERE detector. We consider different DM velocity distributions and momentum-transfer effects. For Xenon and Neon targets, we find that the DM mass can be probed down to as low as (10) MeV, and the derived bounds on the DM-nucleus scattering cross section are sensitive to the high-velocity tails of the DM velocity distribution, which can be altered by orders of magnitude for the different DM velocity distributions in the region MeV.

Direct detection of cosmic ray-boosted puffy dark matter

For the light relativistic dark matter (DM) boosted by high energy cosmic ray, its scattering cross section with the nucleon is sensitively dependent on the momentum-transfer and such an dependence is caused by the mediator in the scattering. For puffy DM particle with a size, the momentum-transfer dependence can also arise from the DM radius effect. All these momentum-transfer dependences should be considered. In this note we study the direct detection limits on the cosmic ray-boosted puffy DM for a simplified model with a light mediator. For comparison, we first re-derive the direct detection limits on the cosmic ray-boosted point-like DM. We display the limits on various planes of parameters and find that the limits for the cosmic ray-boosted puffy DM are stronger than for the point-like DM.

Indirect detection of Dark Matter annihilating into Dark Glueballs

We examine indirect detection of dark matter that annihilates into dark glueballs, which in turn decay into the Standard Model via a range of portals. This arises if the dark matter candidate couples to a confining gauge force without light flavours, representative of many possible complex dark sectors. Such Hidden Valley scenarios are being increasingly considered due to non-detection of minimal models as well as theoretical motivations such as the Twin Higgs solution to the little hierarchy problem. Study of dark glueballs in indirect detection has previously been hampered by the difficulty of modeling their production in dark showers. We use the recent GlueShower code to produce the first constraints on dark matter annihilating via dark glueballs into the Standard Model across photon, antiproton, and positron channels. We also fit the Galactic Centre Excess and use this observation, combined with other astrophysical constraints, to show how multi-channel observations can constrain UV and IR details of the theory, namely the exact decay portal and hadronization behaviour respectively. This provides unique complementary discovery and diagnostic potential to Hidden Valley searches at colliders. It is interesting to note that thermal WIMPs annihilating to 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}(10 GeV) dark glueballs and then the SM via the Twin-Higgs-like decay portal can account for the GCE while respecting other constraints.

The CYGNO experiment: a directional Dark Matter detector with optical readout

We are going to discuss the R&D and the prospects for the CYGNO project, towards the development of an innovative, high precision 3D tracking Time Projection Chamber with optical readout using He:CF4 gas at 1 bar. CYGNO uses a stack of triple thin GEMs for charge multiplication, this induces scintillation in CF4 gas, which is readout by PMTs and sCMOS cameras. High granularity and low readout noise of sCMOS along with high sampling of PMT allows CYGNO to have 3D tracking with head tail capability and particle identification down to O(keV) energy for directional Dark Matter searches and solar neutrino spectroscopy. We will present the most recent R&D results from the CYGNO project, and in particular the overground commissioning of the largest prototype developed so far, LIME with a 33×33 cm2 readout plane and 50 cm of drift length, for a total of 50 litres active volume. We will illustrate the LIME response characterisation between 3.7 keV and 44 keV by means of multiple X-ray sources, and the data Monte-Carlo comparison of simulated sCMOS images in this energy range. Furthermore, we will present current LIME installation, operation and data taking at underground Laboratori Nazionali del Gran Sasso (LNGS), serving as demonstrator for the development of a 0.4 m3 CYGNO detector. We will conclude by mentioning the technical choices and the prospects of the 0.4 m3 detector, as laid out in the Technical Design Report (TDR) recently produced by our collaboration.

Skipper-CCD sensors for the Oscura experiment: requirements and preliminary tests

Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark matter (DM) direct detection search that will reach unprecedented sensitivity to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is planning to operate at SNOLAB with 2070 m overburden, and aims to reach a background goal of less than one event in each electron bin in the 2–10 electron ionization-signal region for the full 30 kg-year exposure, with a radiation background rate of 0.01 dru.[1 dru (differential rate unit) corresponds to 1 event/kg/day/keV.] In order to achieve this goal, Oscura must address each potential source of background events, including instrumental backgrounds. In this work, we discuss the main instrumental background sources and the strategy to control them, establishing a set of constraints on the sensors' performance parameters. We present results from the tests of the first fabricated Oscura prototype sensors, evaluate their performance in the context of the established constraints and estimate the Oscura instrumental background based on these results.

Non-perturbative effects for dark sectors with QCD portals

In this work, we consider a class of dark matter (DM) models where the DM does not directly interact with the Standard Model (SM) particles at the tree-level. Therefore, the coannihilation mechanism is crucial in achieving the correct DM relic abundance, which in turn requires the coannihilating partner to be close in mass to the actual DM particle. In our systematisation of the models’ class, the mediator and the coannihilation partner are assumed to be charged under QCD interactions. This last feature calls for a scrutiny of non-perturbative effects, namely Sommerfeld factors and bound-state formation, on the annihilations of the colored partner. Such non-perturbative effects are illustrated with an example model comprising a scalar leptoquark mediator, a Dirac vector-like fermion coannihilation partner, and a singlet DM fermion. Phenomenological features of this model, namely DM direct and indirect detection prospects, collider implications, and impact on the muon anomalous magnetic moment, are discussed.

Higgs portal majorana fermionic dark matter with the freeze-in mechanism

Abstract We consider a minimal model of fermionic dark matter (DM), in which the Majorana fermion DM χ couples with the Standard Model (SM) Higgs field H through a higher-dimensional term $-{\cal L}\supset H^\dagger H \bar{\chi }\chi /\Lambda$, where Λ is the cutoff scale. We assume that Λ is sufficiently large that DM particles are not in thermal equilibrium with the SM particles throughout the history of the universe. Hence, DM particles are produced only by the freeze-in mechanism. Through a numerical analysis of the freeze-in mechanism, we show contour plots of the DM relic abundance for various values of the DM mass, reheating temperature, and the cutoff scale. We obtain an upper bound of the DM mass and cutoff scale from contour plots on the (mχ, Λ)-plane. We also consider direct DM detection for the parameter regions where the DM relic abundance is consistent with the experimental values. We find that the spin-independent cross section for the elastic scattering with a nucleon is below the current experimental upper bound.

Probing generalized neutrino interactions with the DUNE Near Detector

We explore the prospects of constraining general non standard interactions involving light mediators through elastic neutrino-electron scattering events at the DUNE Near Detector (ND). We furthermore consider the special cases of light vector mediators in motivated models such as U(1)B−L, textrm{U}{(1)}_{L_{mu }-{L}_{tau }} , E6 and left-right symmetry. The present analysis is based on detailed Monte Carlo simulations of the expected DUNE-ND signal taking into account detector resolution effects, realistic backgrounds as well as On-Axis and Off-Axis neutrino spectra. We show that the high intensity neutrino beam available at Fermilab can place competitive constraints surpassing those of low-energy neutrino searches and direct detection dark matter experiments.

Investigation of light dark matter with 2beta decay experiments

Nuclei that are unstable with respect to double beta decay are investigated in this work for a novel dark matter (DM) direct detection approach. In particular, the diagram responsible for the neutrinoless double beta decay can be considered for the possible detection technique of a Majorana DM fermion inelastically scattering on a double beta unstable nucleus, stimulating its decay. The exothermic nature of the stimulated double beta decay would allow the direct detection also of a light DM fermion, a class of DM candidates that are difficult or impossible to investigate with the traditional elastic scattering techniques. The expected signal distribution for different DM masses and the upper limits on the nucleus scattering cross sections, are shown and compared with the existing data for the case of ^{136}Xe nucleus.

Directional detection of dark matter with anisotropic response functions

Directional detection of dark matter with anisotropic response functions

Photomultiplier characterisation and its impact on background for SABRE South

SABRE (Sodium iodide with Active Background REjection) South is a NaI(Tl) based dark matter direct detection experiment located at the Stawell Underground Physics Laboratory (SUPL) [J. Phys. Conf. Ser. 2156, 012064 (2021), arXiv:2205.13849]. It is designed to detect an annual modulation of WIMP recoils as an independent replication of the long-standing DAMA/LIBRA modulation signal. SABRE South will have a low energy threshold of 1 keV in the NaI(Tl) crystal detector and a low experimental background. This requires precise characterisation of the photomultipliers used to understand both their sensitivity at low thresholds and their contribution to the background. We report on the photomultiplier characterisation test bench developed for the crystal detector photomultipliers including studies of the single photon response, transit time, and dark noise. A specific focus is on estimating the contribution to the experimental background of coincident photomultiplier noise due to its predominance at low energy and inability to be modelled using traditional MC simulation.

Global fits of Dirac dark matter effective field theories

In this proceeding, we present results from a global fit of Dirac fermion dark matter (DM) effective field theory (EFT) based on arXiv:2106.02056 using the GAMBIT framework. Here we show results only for the dimension-6 operators that describe the interactions between a gauge-singlet Dirac fermion and Standard Model quarks. Our global fit combines the latest constraints from Planck, direct and indirect DM detection, and the LHC. For DM mass below 100 GeV, it is impossible to simultaneously satisfy all constraints while maintaining the EFT validity at high energies. For higher masses, however, large regions of parameter space remain viable where the EFT is valid and saturates the observed DM abundance.

RemoTES: A new design for the cryogenic NaI detectors of the COSINUS experiment

The increasing statistical significance of the DAMA/LIBRA annual modulation signal is a cause for tension in the field of dark matter direct detection. The COSINUS experiment aims at a model-independent cross-check of the DAMA/LIBRA signal claim, using NaI crystals operated as cryogenic scintillating calorimeters at millikelvin temperatures. Such a setup enables measurement of phonon and scintillation light signals via Transition Edge Sensors (TESs) and allows particle discrimination on an event-by-event basis. The non-standard properties of NaI cause an obstacle when attaching a TES directly onto the surface of the crystal. This can be overcome with the "remoTES" design, where the TES is attached to an external wafer crystal. We present the results from a first successful operation of NaI and other crystals as cryogenic calorimeters with the remoTES design.

Signatures and detection prospects for sub-GeV dark matter with superfluid helium

We explore the possibility of using superfluid helium for direct detection of sub-GeV dark matter (DM). We discuss the relevant phenomenology resulting from the scattering of an incident dark matter particle on a Helium nucleus. Rather than directly exciting quasi-particles, DM in this mass range will interact with a single He atom, triggering an atomic cascade which eventually also includes emission and thermalization of quasi-particles. We present in detail the analytical framework needed for modeling these processes and determining the resulting flux of quasi-particles. We propose a novel method for detecting this flux with modern force-sensitive devices, such as nanoelectro-mechanical system (NEMS) oscillators, and derive the sensitivity projections for a generic sub-GeV DM detection experiment using such sensors.