Dark Matter Mass Research Articles

Simulating realistic self-interacting dark matter models including small and large-angle scattering

Dark matter (DM) self-interactions alter matter distribution on galactic scales and alleviate tensions with observations. A feature of the self-interaction cross section is its angular dependence, which influences offsets between galaxies and DM halos in merging galaxy clusters. While algorithms for modelling mostly forward-dominated or mostly large-angle scatterings exist, incorporating realistic angular dependencies within N-body simulations remains challenging. To efficiently simulate models with a realistic angle dependence, such as light mediator models, we developed, validated, and applied a novel method. We combined existing approaches to describe small- and large-angle scattering regimes within a hybrid scheme. Below a critical angle, the scheme uses the effective description of small-angle scattering via a drag force combined with transverse momentum diffusion, while above the angle, it samples the dependence explicitly. We first verified the scheme using a test set-up with known analytical solutions, and we checked that our results are insensitive to the choice of the critical angle within an expected range. Next, we demonstrated that our scheme speeds up the computations by multiple orders of magnitude for realistic light mediator models. Finally, we applied the method to galaxy cluster mergers. We discuss the sensitivity of the offset between galaxies and DM to the angle dependence of the cross section. Our scheme ensures accurate offsets for mediator mass m_ϕ and DM mass m_χ within the range $0.1v/c m_ϕ/m_χ v/c$, while for larger (smaller) mass ratios, the offsets obtained for isotropic (forward-dominated) self-scattering are approached. Here, v is the typical velocity scale. Equivalently, the upper condition can be expressed as $1.1 tot /σ_ T 10$ for the ratio of the total and momentum transfer cross sections, with the ratio being $1$ (∞) in the isotropic (forward-dominated) limits.

Light dark matter constraints from SuperCDMS HVeV detectors operated underground with an anticoincidence event selection

This article presents constraints on dark-matter-electron interactions obtained from the first underground data-taking campaign with multiple SuperCDMS HVeV detectors operated in the same housing. An exposure of 7.63 g−days is used to set upper limits on the dark-matter-electron scattering cross section for dark matter masses between 0.5 and 1000 MeV/c2, as well as upper limits on dark photon kinetic mixing and axionlike particle axioelectric coupling for masses between 1.2 and 23.3 eV/c2. Compared to an earlier HVeV search, sensitivity was improved as a result of an increased overburden of 225 meters of water equivalent, an anticoincidence event selection, and better pile-up rejection. In the case of dark-matter-electron scattering via a heavy mediator, an improvement by up to a factor of 25 in cross section sensitivity was achieved. Published by the American Physical Society 2025

First Direct Search for Light Dark Matter Using the NEON Experiment at a Nuclear Reactor

We report new results from the neutrino elastic scattering observation with NaI (NEON) experiment in the search for light dark matter (LDM) using 2636 kg·days of NaI(Tl) exposure. The experiment employs an array of NaI(Tl) crystals with a total mass of 16.7 kg, located 23.7 m away from a 2.8 GW thermal power nuclear reactor. We investigated LDM produced by the of dark photons, a well-motivated mechanism generated by high-flux photons during reactor operation. The energy spectra collected during reactor-on and reactor-off periods were compared within the LDM signal region of 1–10 keV. No signal consistent with LDM interaction with electrons was observed, allowing us to set 90% confidence level exclusion limits on the dark matter-electron scattering cross section (σe) across dark matter masses ranging from 1 to 1000 keV/c2. Our results set a 90% confidence level upper limit of σe=3.17×10−35 cm2 for a dark matter mass of 100 keV/c2, marking the best laboratory result in this mass range. Additionally, our search extends the coverage of LDM below 100 keV/c2 for the first time, assuming the specific of dark photons. Published by the American Physical Society 2025

Evaluating the Potential to Constrain Dark Matter Annihilation with Fermi-LAT Observations of Ultrafaint Compact Stellar Systems

Abstract Recent results from numerical simulations and models of galaxy formation suggest that recently discovered ultrafaint compact stellar systems (UFCSs) in the halo of the Milky Way (MW) may be some of the smallest and faintest galaxies. If this is the case, these systems would be attractive targets for indirect searches of weakly interacting massive particle dark matter (DM) annihilation due to their relative proximity and high expected DM content. In this study, we analyze 14.3 yr of γ-ray data collected by the Fermi-Large Area Telescope coincident with 26 UFCSs. No significant excess γ-ray emission is detected, and we present γ-ray flux upper limits for these systems. Assuming that the UFCSs are DM-dominated galaxies consistent with being among the faintest and least massive MW dwarf spheroidal (dSph) satellite galaxies, we derive the projected sensitivity for a DM annihilation signal. We find that observations of UFCSs have the potential to yield some of the most powerful constraints on DM annihilation, with sensitivity comparable to observations of known dSphs and the Galactic center. This result emphasizes the importance of precise kinematic studies of UFCSs to empirically determine their DM content.

Ultradiffuse Dwarf Galaxies Hosting Pseudobulges

Abstract By analyzing data from DESI Legacy Imaging Survey of the dwarf galaxies in the Arecibo Legacy Fast Alfa Survey, we have identified five ultradiffuse galaxies (UDGs) featuring central pseudobulges. These UDGs display blue pseudobulges with Sérsic indices n < 2.5 and effective radii spanning 300–700 pc, along with bluer thin stellar disks exhibiting low surface brightness and expansive effective radii that align with the UDG definition. The rotation velocities of these UDGs, determined using H i line widths and optical inclinations, exceed those of most dwarf galaxies of similar mass, suggesting the high halo spins or substantial dark matter halos. We propose that these UDGs likely formed through mergers of dwarf galaxies lacking old stars in their progenitors, resulting in the development of central bulge-like structures during starbursts triggered by the mergers while also enhancing their halo spin. Subsequent gas accretion facilitated the formation of extended stellar disks. It is also worth noting the possibility that these UDGs could alternatively represent “failed L ⋆ galaxies” with massive dark matter halos but reduced star formation efficiencies. If future high-resolution H i observations confirm the presence of massive halos around these UDGs, they may have formed due to intense AGN feedback in the early Universe and may be the descendants of “little red dots” observed by the James Webb Space Telescope, which are characterized by heightened central black hole masses and intensified accretion and feedback processes in the early Universe.

Implications of the Intriguing Constant Inner Mass Surface Density Observed in Dark Matter Halos

It has long been known that the observed mass surface density of cored dark matter (DM) halos is approximately constant, independently of the galaxy mass (i.e., ρcrc≃constant, with ρc and rc being the central volume density and the radius of the core, respectively). Here, we review the evidence supporting this empirical fact as well as its theoretical interpretation. It seems to be an emergent law resulting from the concentration–halo mass relation predicted by the current cosmological model, where the DM is made of collisionless cold DM particles (CDM). We argue that the prediction ρcrc≃constant is not specific to this particular model of DM but holds for any other DM model (e.g., self-interacting) or process (e.g., stellar or AGN feedback) that redistributes the DM within halos conserving its CDM mass. In addition, the fact that ρcrc≃constant is shown to allow the estimate of the core DM mass and baryon fraction from stellar photometry alone is particularly useful when the observationally expensive conventional spectroscopic techniques are unfeasible.

Minding the gap: Testing natural anomaly-mediated SUSY breaking at high luminosity LHC

While the minimal anomaly-mediated SUSY breaking model (mAMSB) seems ruled out by constraints on Higgs mass, naturalness and wino dark matter, a slightly generalized version dubbed natural AMSB (nAMSB) remains both viable and compelling. Like mAMSB, nAMSB features winos as the lightest gauginos, but unlike mAMSB, nAMSB allows a small μ parameter so that Higgsinos are the lightest of electroweakinos (EWinos). nAMSB spectra depend on the input value of gravitino mass m3/2, where the lower range of m3/2 is excluded by LHC gluino pair searches while a higher m3/2 band is excluded by LHC limits on wino pair production followed by boosted hadronic wino decays. A remaining intermediate gap in m3/2 values remains allowed by present LHC searches, but appears to be completely explorable by high luminosity upgrades of LHC (HL-LHC). We explore a variety of compelling discovery channels that may allow one to close the intermediate gap in m3/2 values: (1) same-sign diboson+ET (SSdB) production arising from wino pair production, leading to same-sign dileptons plus missing ET, (2) trilepton production arising from wino pair production and (3) soft dilepton plus jet events from Higgsino pair production, (4) top-squark pair production. From our signal-to-background analysis along a nAMSB model line, we expect HL-LHC to either discover or rule out the nAMSB model with 3000 fb−1 of integrated luminosity. Published by the American Physical Society 2025

Minimal decaying dark matter: from cosmological tensions to neutrino signatures

The invisible decay of cold dark matter into a slightly lighter dark sector particle on cosmological time-scales has been proposed as a solution to the S 8 tension. In this work we discuss the possible embedding of this scenario within a particle physics framework, and we investigate its phenomenology. We identify a minimal dark matter decay setup that addresses the S 8 tension, while avoiding the stringent constraints from indirect dark matter searches. In our scenario, the dark sector contains two singlet fermions N 1,2, quasi-degenerate in mass, and carrying lepton number so that the heaviest state (N 2) decays into the lightest (N 1) and two neutrinos via a higher-dimensional operator N 2 → N̅ 1νν . The conservation of lepton number, and the small phase-space available for the decay, forbids the decay channels into hadrons and strongly suppresses the decays into photons or charged leptons. We derive complementary constraints on the model parameters from neutrino detectors, freeze-in dark matter production via νν → N 1 N 2, collider experiments and blazar observations, and we show that the upcoming JUNO neutrino observatory could detect signals of dark matter decay for model parameters addressing the S 8 tension if the dark matter mass is below ≃ 1 GeV.

SIMP dark matter during reheating

Strongly interacting massive particle (SIMP) has become one of the promising dark matter (DM) candidates due to its capability of addressing the small-scale anomaly, where the final DM abundance is set via the freeze-out of 3→ 2 or 4→ 2 annihilation process involving solely the dark sector particles. In this work, we explore the freeze-out of SIMP DM during the inflationary reheating epoch. During reheating, the radiation energy density evolves differently based on the shape of inflaton potential and spin of its decay products than the standard radiation-dominated picture; as a result, in this scenario, the freeze-out temperature varies distinctly with DM mass compared to the standard case. Large entropy injection due to inflaton decay demands a smaller cross-section to satisfy the observed relic than the standard radiation-dominated freeze-out case. The required cross-section, satisfying the relic density constraint and the maximum allowed thermally averaged cross-section by the unitarity of the S-matrix, set an upper limit on the DM mass. The upper bound on the mass of the dark matter for 3→2 (4→2) is 1 GeV (7 MeV), assuming a radiation-dominated background. Interstingly, these limits get relaxed to 106 (104) GeV for 3→2 (4→2) SIMP dark matter for quadratic inflaton potential. We find that a small amount of DM parameter space survives for reheating with quadratic inflaton potential after considering the lower bound of reheating temperature, put by the latest CMB observation depending on the inflationary models. In the case of the quartic inflaton potential, the allowed DM parameter space gets reduced compared to the quadratic case.

Insights into dark matter direct detection experiments: decision trees versus deep learning

The detection of Dark Matter (DM) remains a significant challenge in particle physics. This study exploits advanced machine learning models to improve detection capabilities of liquid xenon time projection chamber experiments, utilizing state-of-the-art transformers alongside traditional methods like Multilayer Perceptrons and Convolutional Neural Networks. We evaluate various data representations and find that simplified feature representations, particularly corrected S1 and S2 signals as well as a few shape-related features including the time difference between signals, retain critical information for classification. Our results show that while transformers offer promising performance, simpler models like XGBoost can achieve comparable results with optimal data representations. We also derive exclusion limits in the cross-section versus DM mass parameter space, showing minimal differences between XGBoost and the best performing deep learning models. The comparative analysis of different machine learning approaches provides a valuable reference for future experiments by guiding the choice of models and data representations to maximize detection capabilities.

Spectroscopic confirmation of the galaxy clusters CARLA J0950+2743 at z = 2.363 and CARLA-Ser J0950+2743 at z = 2.243

Galaxy clusters are the largest gravitationally bound structures in the Universe and therefore are a powerful tool for studying mass assembly at different epochs. At z > 2, they provide the unique opportunity to place solid constraints not only on the growth of the dark matter halo, but also on the mechanisms of galaxy quenching and morphological transformation when the Universe was younger than 3.3 Gyr. However, the currently available sample of confirmed z > 2 clusters remains very limited. We present the spectroscopic confirmation of the galaxy cluster CARLA J0950+2743 at z = 2.363 ± 0.005 and a new serendipitously discovered cluster, CARLA-Ser J0950+2743 at z = 2.243 ± 0.008, in the same region. We confirm eight star-forming galaxies in the first and five in the second cluster by detecting [OII], [OIII], and Hα emission lines. The analysis of an archival X-ray Chandra dataset that covers the cluster position revealed a counterpart with a total luminosity of L0.5−5keV = 2.9 ± 0.6 × 1045 erg s−1. Because the depth of the X-ray observations is limited, we cannot distinguish the 1D profile of the source from a point spread function model, but our statistical analysis of the 2D profile favors an extended component that might be associated with a thermal contribution from the intracluster medium. If the extended X-ray emission is due to the hot intracluster medium, the total combined dark matter mass for the two clusters would be M200 ≈ 3.0−0.23(stat)+0.20 −0.85(sys)+1.13 × 1014 M⊙, assuming a ∼30% contribution from the active galactic nucleus. Our two clusters are therefore interesting targets for studies of the structure growth in the cosmological context. However, future investigation will require deeper high-resolution X-ray and spectroscopic observations to rule out the hypotheses that the emission is entirely due to the active galactic nucleus or that it originates from other contaminating radio galaxies and structures.

Constraints on the fuzzy dark matter mass window from high-redshift observables

Constraints on the fuzzy dark matter mass window from high-redshift observables

Ultralight dark matter detection with levitated ferromagnets

Levitated ferromagnets act as ultraprecise magnetometers, which can exhibit high quality factors due to their excellent isolation from the environment. These instruments can be utilized in searches for ultralight dark matter candidates, such as axionlike dark matter or dark-photon dark matter. In addition to being sensitive to an axion-photon coupling or kinetic mixing, which produce physical magnetic fields, ferromagnets are also sensitive to the effective magnetic field (or “axion wind”) produced by an axion-electron coupling. While the dynamics of a levitated ferromagnet in response to a dc magnetic field have been well studied, all of these couplings would produce ac fields. In this work, we study the response of a ferromagnet to an applied ac magnetic field and use these results to project their sensitivity to axion and dark-photon dark matter. We pay special attention to the direction of motion induced by an applied ac field, in particular, whether it precesses around the applied field (similar to an electron spin) or librates in the plane of the field (similar to a compass needle). We show that existing levitated ferromagnet setups can already have comparable sensitivity to an axion-electron coupling as comagnetometer or torsion balance experiments. In addition, future setups can become sensitive probes of axion-electron coupling, dark-photon kinetic mixing, and axion-photon coupling, for ultralight dark matter masses mDM≲feV. Published by the American Physical Society 2024

Resonant Conversion of Wave Dark Matter in the Ionosphere

We consider resonant wavelike dark matter conversion into low-frequency radio waves in the Earth’s ionosphere. Resonant conversion occurs when the dark matter mass and the plasma frequency coincide, defining a range mDM∼10−9–10−8 eV where this approach is best suited. Owing to the nonrelativistic nature of dark matter and the typical variational scale of the Earth’s ionosphere, the standard linearized approach to computing dark matter conversion is not suitable. We therefore solve a second-order boundary-value problem, effectively framing the ionosphere as a driven cavity filled with a positionally varying plasma. An electrically small dipole antenna targeting the generated radio waves can be orders of magnitude more sensitive to dark photon and axionlike particle dark matter in the relevant mass range. This Letter opens up a promising way of testing hitherto unexplored parameter space that could be further improved with a dedicated instrument. Published by the American Physical Society 2024

Attenuation of cosmic ray electron boosted dark matter

We consider a model of boosted dark matter (DM), where a fraction of DM is upscattered to relativistic energies by cosmic ray electrons. Such interactions responsible for boosting the DM also attenuate its flux at the Earth. Considering a simple model of constant interaction cross section, we make analytical estimates of the variation of the attenuation ceiling with the DM mass and confirm it numerically. We then extend our analysis to a Z′-mediated leptophilic DM model. We show that the attenuation ceiling remains nearly model independent for DM and mediator particles heavier than the electron, challenging some previous discussions on this topic. Using the XENONnT direct detection experiment, we illustrate how constraints based on energy-dependent scattering can significantly differ from those based on an assumed constant cross section. This highlights the importance of reevaluating these constraints in the context of specific models. Published by the American Physical Society 2024

Constraints on dark matter mass in an F(R) gravity model with an additional R2 correction term

Abstract The dominance of dark matter and dark energy presents one of the most significant challenges in cosmology. The chameleon mechanism in F(R) gravity offers a potential solution to this issue. However, many F(R) models encounter a problem known as the singularity problem, where the scalaron mass becomes too heavy to function as dark matter. This study aims to address the singularity problem within the Gogoi-Goswami F(R) model by incorporating an additional R 2 correction term. Assuming the scalaron functions as chameleonic dark matter, its mass must satisfy constraints across various scales, including the electroweak transition phase and galactic structures. By adopting a hierarchical scale with R 0 ≪ R c < m ¯ 2 , where R 0 is the Ricci scalar at late-time de Sitter space and m ¯ represents the inflaton mass scale in Starobinsky's model, and assuming R c ≃ 1 GeV2, the mass constraints during the electroweak transition can be satisfied with α ≃ 1.05. Nevertheless, meeting the required mass constraints on a galactic scale remains a challenge. Alternatively, if R c is considered relevant only in the current universe, such that R 0 ≪ R c ≪ m ¯ 2 , these dark matter mass constraints can be more easily met. For example, setting R c ≃ m φ 2 ( gal ) ≃ ( 1 0 − 32 ) 2 GeV 2 effectively satisfies these constraints.

The hot circumgalactic medium in the eROSITA All-Sky Survey. III. Star-forming and quiescent galaxies

The galaxy population shows a characteristic bimodal distribution based on the star formation activity and is sorted into star-forming or quiescent. These two subpopulations have a tendency to be located in different mass halos. The circumgalactic medium (CGM), as the gas repository for star formation, might contain the answer to the mystery of the formation of such bimodality. Here we consider the bimodality of the galaxy population and study the difference between the properties of the hot CGM around star-forming and quiescent galaxies. We used the X-ray data from the first four SRG/eROSITA all-sky surveys (eRASS:4). We selected central star-forming and quiescent galaxies from the Sloan Digital Sky Survey DR7 with stellar mass $10.0< or halo mass $11.5< 200m /M_ within spectroscopic redshift spec <0.2$, and we built approximately volume-limited galaxy samples. We stacked the X-ray emission around star-forming and quiescent galaxies, respectively. We masked detected point sources and carefully modeled the X-ray emission from unresolved active galaxy nuclei (AGN) and X-ray binaries (XRB) to detect the X-ray emission from the hot CGM. We measured the X-ray surface brightness ($S_ X, CGM $) profiles and integrated the X-ray emission from hot CGM within $R_ 500c $ ($L_ X, CGM $) to provide the scaling relations between $L_ X, CGM $ and galaxies' stellar or halo mass. We detect extended X-ray emission from the hot CGM around star-forming galaxies with $ and quiescent galaxies with $ extending out to 500c $. The $S_ X, CGM $ profile of quiescent galaxies follows a beta model with $ 0.4$, where beta quantifies the slope of the profile. Star-forming galaxies with median stellar masses $ *,med /M_ = 10.7, 11.1, 11.3$ have X, CGM erg/s$, while for quiescent galaxies with $ *,med /M_ X, CGM erg/s$. Notably, quiescent galaxies with $ *,med /M_ > 11.0$ exhibit brighter hot CGM than their star-forming counterparts. In halo mass bins, we detect similar X-ray emission around star-forming and quiescent galaxies with $ 200m /M_ > 12.5$, suggesting that galaxies in the same mass dark matter halos host equally bright hot CGM. We emphasize that the observed X, CGM - M_ 500c $ relations of star-forming and quiescent galaxies are sensitive to the stellar-to-halo mass relation (SHMR). A comparison with cosmological hydrodynamical simulations (EAGLE, TNG100, and SIMBA) reveals varying degrees of agreement, contingent on the simulation and the specific stellar or halo mass ranges considered. Either selected in stellar mass or halo mass, the star-forming galaxies do not host brighter stacked X-ray emission from the hot CGM than their quiescent counterparts at the same mass range. The result provides useful constraints on the extent of feedback's impacts as a mechanism for quenching star formation as implemented in current cosmological simulations.

The Large Magellanic Cloud: expanding the low-mass parameter space of dark matter direct detection

We investigate how the Large Magellanic Cloud (LMC) impacts the predicted signals in near-future direct detection experiments for non-standard dark matter (DM) interactions, using the Auriga cosmological simulations. We extract the local DM distribution of a simulated Milky Way-like halo that has an LMC analogue and study the expected signals in DarkSide-20k, SBC, DARWIN/XLZD, SuperCDMS, NEWS-G, and DarkSPHERE considering DM-nucleon effective interactions, as well as inelastic DM scattering. We find that the LMC causes substantial shifts in direct detection exclusion limits towards smaller cross sections and DM masses for all non-relativistic effective field theory (NREFT) operators, with the impact being highly pronounced for velocity-dependent operators at low DM masses. For inelastic DM, where the DM particle up-scatters to a heavier state, the LMC shifts the direct detection exclusion limits towards larger DM mass splitting and smaller cross sections. Thus, we show that the LMC significantly expands the parameter space that can be probed by direct detection experiments towards smaller DM-nucleon cross sections for all NREFT operators and larger values of mass splitting for inelastic DM.

Improved treatment of bosonic dark matter dynamics in neutron stars: consequences and constraints

It is conceivable that a bosonic dark matter (DM) with non-gravitational interactions with SM particles will be accumulated at the center of a neutron star (NS) and can lead to black hole formation. In contrast to previous works with a fixed NS temperature, we dynamically determine the formation of Bose-Einstein condensate (BEC) for a given set of DM parameters, namely the DM-neutron scattering cross-section (σχn), the thermal average of DM annihilation cross-section (⟨σv⟩) and the DM mass (mχ). For both non-annihilating and annihilating DM with ⟨σv⟩ ≲ 10-26 cm3 s-1, the BEC forms for mχ ≲ 10 TeV. In case of non-annihilating DM, observations of old NS allows σχn ≲ 10-52 cm2 for 10 MeV ≤ mχ ≲ 10 GeV (with BEC) and σχn ≲ 10-47 cm2 for 5 TeV ≲ mχ ≲ 30 PeV (without BEC). This analysis shows that the electroweak mass window, 10 GeV ≲ mχ ≲ 5 TeV is essentially unconstrained by NS observations and therefore is subject only to direct detection experiments. In the annihilating DM scenario, the exclusion limits on DM parameters become weaker and even vanish for typical WIMP annihilation cross-section. However, the late-time heating of the NS enables us to probe the region with σχn ≳ 10-47 cm2, using the James Webb Space Telescope in the foreseeable future. When our results are viewed in the context of indirect searches of DM, it provides a lower limit on the ⟨σv⟩, which is sensitive to the DM thermal state.

Large Dark Matter Content and Steep Metallicity Profile Predicted for Ultradiffuse Galaxies Formed in High-spin Halos

We study the stellar properties of a sample of simulated ultradiffuse galaxies (UDGs) with stellar mass M ⋆ = 107.5–109 M ⊙, selected from the TNG50 simulation, where UDGs form mainly in high-spin dwarf-mass halos. We divide our sample into star-forming and quenched UDGs, finding good agreement with the stellar assembly history measured in observations. Star-forming UDGs and quenched UDGs with M ⋆ ≥ 108 M ⊙ in our sample are particularly inefficient at forming stars, having 2–10 times less stellar mass than non-UDGs for the same virial mass halo. These results are consistent with recent mass inferences in UDG samples and suggest that the most inefficient UDGs arise from a late assembly of the dark matter mass followed by a stellar growth that is comparatively slower (for star-forming UDGs) or that was interrupted due to environmental removal of the gas (for quenched UDGs). Regardless of efficiency, UDGs are 60% poorer in [Fe/H] than the population of non-UDGs at a fixed stellar mass, with the most extreme objects having metal content consistent with the simulated mass–metallicity relation at z ∼ 2. Quenched UDGs stop their star formation in shorter timescales than non-UDGs of similar mass and are, as a consequence, alpha enhanced with respect to non-UDGs. We identify metallicity profiles in UDGs as a potential avenue to distinguish between different formation paths for these galaxies, where gentle formation as a result of high-spin halos would present well-defined declining metallicity radial profiles while powerful-outflows or tidal stripping formation models would lead to flatter or constant metallicity as a function of radius due to the inherent mixing of stellar orbits.