Novel Direct Detection Constraints on Light Dark Matter

Prospects for Light Dark Matter Searches at Large-Volume Neutrino Detectors

We propose a new approach to search for light dark matter (DM), with keV-GeV mass, via inelastic nucleus scattering at large-volume neutrino detectors such as Borexino, DUNE, Super-K, Hyper-K, and JUNO. The approach uses inelastic nuclear scattering of cosmic-ray boosted DM, enabling a low-background search for DM in these experiments. Large neutrino detectors, with higher thresholds than dark matter detectors, can be used, since the nuclear deexcitation lines are O(10)  MeV. Using a hadrophilic dark-gauge-boson-portal model as a benchmark, we show that the nuclear inelastic channels generally provide better sensitivity than the elastic scattering for a large region of light DM parameter space.

Supernova-Neutrino-Boosted Dark Matter from All Galaxies

It has been recently proposed that the boosted dark matter (BDM) by supernova neutrinos (SNν) from SN1987a or from the next Galactic supernova (SN) can serve as a novel component to probe nonvanishing interaction between dark matter (DM) and the standard model leptons [Y.-H. Lin et al., Phys. Rev. Lett. 130, 111002 (2023)PRLTAO0031-900710.1103/PhysRevLett.130.111002 and Y.-H. Lin et al., Phys. Rev. D 108, 083013 (2023)PRVDAQ2470-001010.1103/PhysRevD.108.083013]. In this Letter, we extend this concept and evaluate the present-day diffuse flux of SNν BDM originated from all galaxies at higher redshifts. We show that by considering this diffuse BDM (DBDM) component, the best sensitivity on the product of the energy-independent DM-ν and DM-electron cross sections, sqrt[σ_{χν}σ_{χe}]≃O(10^{-37})  cm^{2} for sub-MeV DM, can be obtained with large-size neutrino experiments such as Super-Kamiokande or Hyper-Kamiokande, surpassing the estimated SNν BDM bound from SN1987a. We also examine the impact due to the presence of DM spikes around the supermassive black holes in galaxies on SNν BDM and DBDM. Our results suggest that both the DBDM and the SNν BDM probes are robust to the uncertain properties of DM spikes, unless the next Galactic SN happens to occur at a location extremely close to or right behind the Galactic Center along the SN line of sight.

Search for Cosmic-Ray Boosted Sub-MeV Dark-Matter-Electron Scattering in PandaX-4T

We report the first search for the elastic scatterings between cosmic-ray boosted sub-MeV dark matter (DM) and electrons in the PandaX-4T liquid xenon experiment. Sub-MeV DM particles can be accelerated by scattering with electrons in the cosmic rays and produce detectable electron recoil signals in the detector. Using the commissioning data from PandaX-4T of 0.63  tonne·year exposure, we set new constraints on DM-electron scattering cross sections for DM masses ranging from 10  eV/c^{2} to 3  keV/c^{2}.

Experimental Limits on Solar Reflected Dark Matter with a New Approach on Accelerated-Dark-Matter-Electron Analysis in Semiconductors

Recently a dark matter-electron (DM-electron) paradigm has drawn much attention. Models beyond the standard halo model describing DM accelerated by high energy celestial bodies are under intense examination as well. In this Letter, a velocity components analysis (VCA) method dedicated to swift analysis of accelerated DM-electron interactions via semiconductor detectors is proposed and the first HPGe detector-based accelerated DM-electron analysis is realized. Utilizing the method, the first germanium based constraint on sub-GeV solar reflected DM-electron interaction is presented with the 205.4  kg·day dataset from the CDEX-10 experiment. In the heavy mediator scenario, our result excels in the mass range of 5-15  keV/c^{2}, achieving a 3 orders of magnitude improvement comparing with previous semiconductor experiments. In the light mediator scenario, the strongest laboratory constraint for DM lighter than 0.1  MeV/c^{2} is presented. The result proves the feasibility and demonstrates the vast potential of the VCA technique in future accelerated DM-electron analyses with semiconductor detectors.

Search for Boosted Dark Matter in COSINE-100

We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using the COSINE-100 array of NaI(Tl) crystal detectors at the Yangyang Underground Laboratory. The signal would be an excess of events with energies above 4 MeV over the well-understood background. Because no excess of events are observed in a 97.7  kg·yr exposure, we set limits on BDM interactions under a variety of hypotheses. Notably, we explored the dark photon parameter space, leading to competitive limits compared to direct dark photon search experiments, particularly for dark photon masses below 4 MeV and considering the invisible decay mode. Furthermore, by comparing our results with a previous BDM search conducted by the Super-Kamionkande experiment, we found that the COSINE-100 detector has advantages in searching for low-mass dark matter. This analysis demonstrates the potential of the COSINE-100 detector to search for MeV electron recoil signals produced by the dark sector particle interactions.

Starburst Galactic Nuclei as Light Dark Matter Laboratories

Starburst galaxies are well-motivated astrophysical emitters of high-energy gamma rays. They are well-known cosmic-ray "reservoirs," thanks to their expected large magnetic field turbulence which confine high-energy protons for ∼10^{5}  years. Over such long times, cosmic-ray transport can be significantly affected by scatterings with sub-GeV dark matter. Here we point out that this scattering distorts the cosmic-ray spectrum, and the distortion can be indirectly observed by measuring the gamma rays produced by cosmic rays via hadronic collisions. Present gamma-ray data show no sign of such a distortion, leading to stringent bounds on the cross section between protons and dark matter. These are highly complementary with current bounds and have large room for improvement with the future gamma-ray measurements in the 0.1-10 TeV range from the Cherenkov Telescope Array, which can strengthen the limits by as much as 2 orders of magnitude.

Search for Light Dark Matter from the Atmosphere in PandaX-4T

We report a search for light dark matter produced through the cascading decay of η mesons, which are created as a result of inelastic collisions between cosmic rays and Earth's atmosphere. We introduce a new and general framework, publicly accessible, designed to address boosted dark matter specifically, with which a full and dedicated simulation including both elastic and quasielastic processes of Earth attenuation effect on the dark matter particles arriving at the detector is performed. In the PandaX-4T commissioning data of 0.63  tonne·year exposure, no significant excess over background is observed. The first constraints on the interaction between light dark matter generated in the atmosphere and nucleus through a light scalar mediator are obtained. The lowest excluded cross section is set at 5.9×10^{-37}  cm^{2} for a dark matter mass of 0.1  MeV/c^{2} and mediator mass of 300  MeV/c^{2}. The lowest upper limit of η to the dark matter decay branching ratio is 1.6×10^{-7}.

Analytic Approach to Light Dark Matter Propagation

If dark matter interacts too strongly with nuclei, it could be slowed to undetectable speeds in Earth's crust or atmosphere before reaching a detector. For sub-GeV dark matter, approximations appropriate for heavier dark matter fail, necessitating the use of computationally expensive simulations. We present a new, analytic approximation for modeling attenuation of light dark matter in Earth. We show that our approach agrees well with Monte Carlo results, and can be much faster at large cross sections. We use this method to reanalyze constraints on subdominant dark matter.

Searching for Afterglow: Light Dark Matter Boosted by Supernova Neutrinos

A novel analysis is performed, incorporating time-of-flight (TOF) information to study the interactions of dark matter (DM) with standard model particles. After supernova (SN) explosions, DM with mass m_{χ}≲O(MeV) in the halo can be boosted by SN neutrinos (SNν) to relativistic speed. The SNν boosted DM (BDM) arrives on Earth with TOF which depends only on m_{χ} and is independent of the cross section. These BDMs can interact with detector targets in low-background experiments and manifest as afterglow events after the arrival of SNν. The characteristic TOF spectra of the BDM events can lead to large background suppression and unique determination of m_{χ}. New cross section constraints on sqrt[σ_{χe}σ_{χν}] are derived from SN1987a in the Large Magellanic Cloud with data from the Kamiokande and Super-Kamiokande experiments. Potential sensitivities for the next galactic SN with Hyper-Kamiokande are projected. This analysis extends the existing bounds on sqrt[σ_{χe}σ_{χν}] over a broad range of r_{χ}=σ_{χν}/σ_{χe}. In particular, the improvement is by 1-3 orders of magnitude for m_{χ}<O(100  keV) for σ_{χe}∼σ_{χν}. Prospects of exploiting TOF information in other astrophysical systems to probe exotic physics with other DM candidates are discussed.

Blazar Constraints on Neutrino-Dark Matter Scattering

Neutrino emission in coincidence with gamma rays has been observed from the blazar TXS 0506+056 by the IceCube telescope. Neutrinos from the blazar had to pass through a dense spike of dark matter (DM) surrounding the central black hole. The observation of such a neutrino implies new upper bounds on the neutrino-DM scattering cross section as a function of DM mass. The constraint is stronger than existing ones for a range of DM masses, if the cross section rises linearly with energy. For constant cross sections, competitive bounds are also possible, depending on details of the DM spike.

Search for Cosmic-Ray Boosted Sub-GeV Dark Matter Using Recoil Protons at Super-Kamiokande

We report a search for cosmic-ray boosted dark matter with protons using the 0.37  megaton×years data collected at Super-Kamiokande experiment during the 1996-2018 period (SKI-IV phase). We searched for an excess of proton recoils above the atmospheric neutrino background from the vicinity of the Galactic Center. No such excess is observed, and limits are calculated for two reference models of dark matter with either a constant interaction cross section or through a scalar mediator. This is the first experimental search for boosted dark matter with hadrons using directional information. The results present the most stringent limits on cosmic-ray boosted dark matter and exclude the dark matter-nucleon elastic scattering cross section between 10^{-33}cm^{2} and 10^{-27}cm^{2} for dark matter mass from 1  MeV/c^{2} to 300  MeV/c^{2}.

Maximizing Direct Detection with Highly Interactive Particle Relic Dark Matter

We estimate the maximum direct detection cross section for sub-GeV dark matter (DM) scattering off nucleons. For DM masses in the range 10 keV-100 MeV, cross sections greater than 10^{-36}-10^{-30}  cm^{2} seem implausible. We present a DM candidate which realizes this maximum cross section: highly interactive particle relics (HYPERs). After HYPERs freeze-in, a dark sector phase transition decreases the mediator's mass. This increases the HYPER's direct detection cross section without impacting its abundance or measurements of big bang nucleosynthesis and the cosmic microwave background.

Scattering Searches for Dark Matter in Subhalos: Neutron Stars, Cosmic Rays, and Old Rocks

In many cosmologies dark matter clusters on subkiloparsec scales and forms compact subhalos, in which the majority of Galactic dark matter could reside. Null results in direct detection experiments since their advent four decades ago could then be the result of extremely rare encounters between the Earth and these subhalos. We investigate alternative and promising means to identify subhalo dark matter interacting with standard model particles: (1) subhalo collisions with old neutron stars can transfer kinetic energy and brighten the latter to luminosities within the reach of imminent infrared, optical, and ultraviolet telescopes; we identify new detection strategies involving single-star measurements and Galactic disk surveys, and obtain the first bounds on self-interacting dark matter in subhalos from the coldest known pulsar, PSR J2144-3933; (2) subhalo dark matter scattering with cosmic rays results in detectable effects; (3) historic Earth-subhalo encounters can leave dark matter tracks in Paleolithic minerals deep underground. These searches could discover dark matter subhalos weighing between gigaton and solar masses, with corresponding dark matter cross sections and masses spanning tens of orders of magnitude.

Direct Detection Constraints on Blazar-Boosted Dark Matter

We explore the possibility that relativistic protons in the extremely powerful jets of blazars may boost via elastic collisions the dark matter particles in the surroundings of the source to high energies. We concentrate on two sample blazars, TXS 0506+056, towards which IceCube recently reported evidence for a high-energy neutrino flux, and BL Lacertae, a representative nearby blazar. We find that the dark matter flux at Earth induced by these sources may be sizable, larger than the flux associated with the analogous process of dark matter boosted by galactic cosmic rays, and relevant to access direct detection for dark matter particle masses lighter than 1 GeV. From the null detection of a signal by XENON1T, MiniBooNE, and Borexino, we derive limits on dark matter-nucleus spin-independent and spin-dependent cross sections which, depending on the modelization of the source, improve on other currently available bounds for light dark matter candidates of 1 up to 5 orders of magnitude.

Search for Cosmic-Ray Boosted Sub-GeV Dark Matter at the PandaX-II Experiment

We report a novel search for the cosmic-ray boosted dark matter using the 100  tonne·day full dataset of the PandaX-II detector located at the China Jinping Underground Laboratory. With the extra energy gained from the cosmic rays, sub-GeV dark matter particles can produce visible recoil signals in the detector. The diurnal modulations in rate and energy spectrum are utilized to further enhance the signal sensitivity. Our result excludes the dark matter-nucleon elastic scattering cross section between 10^{-31} and 10^{-28}  cm^{2} for dark matter masses from 0.1  MeV/c^{2} to 0.1  GeV/c^{2}, with a large parameter space previously unexplored by experimental collaborations.

Limits on the Light Dark Matter-Proton Cross Section from Cosmic Large-Scale Structure

We set the strongest limits to date on the velocity-independent dark matter (DM)-proton cross section σ for DM masses m=10  keV to 100 GeV, using large-scale structure traced by the Lyman-alpha forest: e.g., a 95% lower limit σ<6×10^{-30}  cm^{2}, for m=100  keV. Our results complement direct detection, which has limited sensitivity to sub-GeV DM. We use an emulator of cosmological simulations, combined with data from the smallest cosmological scales used to date, to model and search for the imprint of primordial DM-proton collisions. Cosmological bounds are improved by up to a factor of 25.

Coherent Scattering of Low Mass Dark Matter from Optically Trapped Sensors

We propose a search for low mass dark matter particles through momentum recoils caused by their scattering from trapped, nanometer-scale objects. Our projections show that even with a modest array of femtogram-mass sensors, parameter space beyond the reach of existing experiments can be explored. The case of smaller, attogram-mass sensors is also analyzed-where dark matter can coherently scatter from the entire sensor-enabling a large enhancement in the scattering cross-section relative to interactions with single nuclei. Large arrays of such sensors have the potential to investigate new parameter space down to dark matter masses as low as 10 keV. If recoils from dark matter are detected by such sensors, their inherent directional sensitivity would allow an unambiguous identification of a dark matter signal.

Stellar Shocks from Dark Matter Asteroid Impacts

Macroscopic dark matter is almost unconstrained over a wide "asteroidlike" mass range, where it could scatter on baryonic matter with geometric cross section. We show that when such an object travels through a star, it produces shock waves that reach the stellar surface, leading to a distinctive transient optical, UV, and x-ray emission. This signature can be searched for on a variety of stellar types and locations. In a dense globular cluster, such events occur far more often than flare backgrounds, and an existing UV telescope could probe orders of magnitude in dark matter mass in one week of dedicated observation.

Exoplanets as Sub-GeV Dark Matter Detectors

We present exoplanets as new targets to discover dark matter (DM). Throughout the Milky Way, DM can scatter, become captured, deposit annihilation energy, and increase the heat flow within exoplanets. We estimate upcoming infrared telescope sensitivity to this scenario, finding actionable discovery or exclusion searches. We find that DM with masses above about an MeV can be probed with exoplanets, with DM-proton and DM-electron scattering cross sections down to about 10^{-37}  cm^{2}, stronger than existing limits by up to six orders of magnitude. Supporting evidence of a DM origin can be identified through DM-induced exoplanet heating correlated with galactic position, and hence DM density. This provides new motivation to measure the temperature of the billions of brown dwarfs, rogue planets, and gas giants peppered throughout our Galaxy.

Prospects for beyond the Standard Model physics searches at the Deep Underground Neutrino Experiment: DUNE Collaboration

The Deep Underground Neutrino Experiment (DUNE) will be a powerful tool for a variety of physics topics. The high-intensity proton beams provide a large neutrino flux, sampled by a near detector system consisting of a combination of capable precision detectors, and by the massive far detector system located deep underground. This configuration sets up DUNE as a machine for discovery, as it enables opportunities not only to perform precision neutrino measurements that may uncover deviations from the present three-flavor mixing paradigm, but also to discover new particles and unveil new interactions and symmetries beyond those predicted in the Standard Model (SM). Of the many potential beyond the Standard Model (BSM) topics DUNE will probe, this paper presents a selection of studies quantifying DUNE's sensitivities to sterile neutrino mixing, heavy neutral leptons, non-standard interactions, CPT symmetry violation, Lorentz invariance violation, neutrino trident production, dark matter from both beam induced and cosmogenic sources, baryon number violation, and other new physics topics that complement those at high-energy colliders and significantly extend the present reach.

Constraints on Dark Matter Properties from Observations of Milky Way Satellite Galaxies

We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and marginalizes over uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk. Our results are consistent with the cold, collisionless DM paradigm and yield the strongest cosmological constraints to date on particle models of warm, interacting, and fuzzy dark matter. At 95% confidence, we report limits on (i) the mass of thermal relic warm DM, m_{WDM}>6.5  keV (free-streaming length, λ_{fs}≲10h^{-1}  kpc), (ii) the velocity-independent DM-proton scattering cross section, σ_{0}<8.8×10^{-29}  cm^{2} for a 100 MeV DM particle mass [DM-proton coupling, c_{p}≲(0.3  GeV)^{-2}], and (iii) the mass of fuzzy DM, m_{ϕ}>2.9×10^{-21}  eV (de Broglie wavelength, λ_{dB}≲0.5  kpc). These constraints are complementary to other observational and laboratory constraints on DM properties.

Diurnal Effect of Sub-GeV Dark Matter Boosted by Cosmic Rays

We point out a new type of diurnal effect for the cosmic ray boosted dark matter (DM). The DM-nucleon interactions not only allow the direct detection of DM with nuclear recoils but also allow cosmic rays to scatter with and boost the nonrelativistic DM to higher energies. If the DM-nuclei scattering cross sections are sufficiently large, the DM flux is attenuated as it propagates through the Earth, leading to a strong diurnal modulation. This diurnal modulation provides another prominent signature for the direct detection of boosted sub-GeV DM, in addition to signals with higher recoil energy.

Shedding new light on sterile neutrinos from XENON1T experiment

The XENON1T collaboration recently reported the excess of events from recoil electrons, possibly giving an insight into new area beyond the Standard Model (SM) of particle physics. We try to explain this excess by considering effective interactions between the sterile neutrinos and the SM particles. In this paper, we present an effective model based on one-particle-irreducible interaction vertices at low energies that are induced from the SM gauge symmetric four-fermion operators at high energies. The effective interaction strength is constrained by the SM precision measurements, astrophysical and cosmological observations. We introduce a novel effective electromagnetic interaction between sterile neutrinos and SM neutrinos, which can successfully explain the XENON1T event rate through inelastic scattering of the sterile neutrino dark matter from Xenon electrons. We find that sterile neutrinos with masses around 90 keV and specific effective coupling can fit well with the XENON1T data where the best fit points preserving DM constraints and possibly describe the anomalies in other experiments.

New Physics of Strong Interaction and Dark Universe

The history of dark universe physics can be traced from processes in the very early universe to the modern dominance of dark matter and energy. Here, we review the possible nontrivial role of strong interactions in cosmological effects of new physics. In the case of ordinary QCD interaction, the existence of new stable colored particles such as new stable quarks leads to new exotic forms of matter, some of which can be candidates for dark matter. New QCD-like strong interactions lead to new stable composite candidates bound by QCD-like confinement. We put special emphasis on the effects of interaction between new stable hadrons and ordinary matter, formation of anomalous forms of cosmic rays and exotic forms of matter, like stable fractionally charged particles. The possible correlation of these effects with high energy neutrino and cosmic ray signatures opens the way to study new physics of strong interactions by its indirect multi-messenger astrophysical probes.

New Freezeout Mechanism for Strongly Interacting Dark Matter

We present a new mechanism for thermally produced dark matter, based on a semi-annihilation-like process, χ+χ+SM→χ+SM, with intriguing consequences for the properties of dark matter. First, its mass is low, ≲1  GeV (but ≳5  keV to avoid structure-formation constraints). Second, it is strongly interacting, leading to kinetic equilibrium between the dark and visible sectors, avoiding the structure-formation problems of χ+χ+χ→χ+χ models. Third, in the 3→2 process, one dark matter particle is consumed, giving the standard-model particle a monoenergetic recoil. We show that this new scenario is presently allowed, which is surprising (perhaps a "minor miracle"). However, it can be systematically tested by novel analyses in present and near-term experiments. In particular, the Co-SIMP model for thermal-relic dark matter can explain the XENON1T excess.

Finite-Size Dark Matter and its Effect on Small-Scale Structure

If dark matter has a finite size that is larger than its Compton wavelength, the corresponding self-interaction cross section decreases with the velocity. We investigate the implications of this puffy dark matter for addressing the small-scale problems of the Λ cold dark matter model and show that the way the nonrelativistic cross section varies with the velocity is largely independent of the dark matter internal structure. Even in the presence of a light particle mediating self-interactions, we find that the finite-size effect may dominate the velocity dependence. We present an explicit example in the context of a QCD-like theory and discuss possible ways to differentiate puffy dark matter from the usual light-mediator scenarios. Particularly relevant for this are low-threshold direct-detection experiments and indirect signatures associated with the internal structure of dark matter.

Relation between the Migdal Effect and Dark Matter-Electron Scattering in Isolated Atoms and Semiconductors

A key strategy for sub-GeV dark matter direct detection is searches for small ionization signals that arise from dark matter-electron scattering or from the "Migdal" effect in dark matter-nucleus scattering. We show that the theoretical description of both processes is closely related, allowing for a principal mapping between them. We explore this for noble-liquid targets and, for the first time, estimate the Migdal effect in semiconductors using a crystal form factor. We present new constraints using XENON10, XENON100, and SENSEI data, and give projections for proposed experiments.

Detecting Light Dark Matter via Inelastic Cosmic Ray Collisions

Direct detection experiments relying on nuclear recoil signatures lose sensitivity to sub-GeV dark matter for typical galactic velocities. This sensitivity is recovered if there exists another source of flux with higher momenta. Such an energetic flux of light dark matter could originate from the decay of mesons produced in inelastic cosmic ray collisions. We compute this novel production mechanism-a cosmic beam dump experiment-and estimate the resulting limits from XENON1T and LZ. We find that the dark matter flux from inelastic cosmic rays colliding with atmospheric nuclei can dominate over the flux from elastic collisions with relic dark matter. The limits that we obtain for hadrophilic scalar mediator models are competitive with those from MiniBoone for light MeV-scale mediator masses.