Dark Matter Search Results from a One Ton-Year Exposure of XENON1T

Results on Low-Mass Weakly Interacting Massive Particles from an 11 kg d Target Exposure of DAMIC at SNOLAB

We present constraints on the existence of weakly interacting massive particles (WIMPs) from an 11 kg d target exposure of the DAMIC experiment at the SNOLAB underground laboratory. The observed energy spectrum and spatial distribution of ionization events with electron-equivalent energies >200  eV_{ee} in the DAMIC CCDs are consistent with backgrounds from natural radioactivity. An excess of ionization events is observed above the analysis threshold of 50  eV_{ee}. While the origin of this low-energy excess requires further investigation, our data exclude spin-independent WIMP-nucleon scattering cross sections σ_{χ-n} as low as 3×10^{-41}  cm^{2} for WIMPs with masses m_{χ} from 7 to 10  GeV c^{-2}. These results are the strongest constraints from a silicon target on the existence of WIMPs with m_{χ}<9  GeV c^{-2} and are directly relevant to any dark matter interpretation of the excess of nuclear-recoil events observed by the CDMS silicon experiment in 2013.

Towards a fundamental safe theory of composite Higgs and dark matter

We present a novel paradigm that allows to define a composite theory at the electroweak scale that is well defined all the way up to any energy by means of safety in the UV. The theory flows from a complete UV fixed point to an IR fixed point for the strong dynamics (which gives the desired walking) before generating a mass gap at the TeV scale. We discuss two models featuring a composite Higgs, Dark Matter and partial compositeness for all SM fermions. The UV theories can also be embedded in a Pati-Salam partial unification, thus removing the instability generated by the U ( 1 ) running. Finally, we find a Dark Matter candidate still allowed at masses of 260 GeV, or 1.5-2 TeV, where the latter mass range will be covered by next generation direct detection experiments.

What Is the Price of Abandoning Dark Matter? Cosmological Constraints on Alternative Gravity Theories

Any successful alternative gravity theory that obviates the need for dark matter must fit our cosmological observations. Measurements of microwave background polarization trace the large-scale baryon velocity field at recombination and show very strong O(1) baryon acoustic oscillations. Measurements of the large-scale structure of galaxies at low redshift show much weaker features in the spectrum. If the alternative gravity theory's dynamical equations for the growth rate of structure are linear, then the density field growth can be described by a Green's function: δ(x[over →],t)=δ(x[over →],t^{'})G(x,t,t^{'}). We show that the Green's function G(x,t,t^{'}) must have dramatic features that erase the initial baryon oscillations. This implies an acceleration law that changes sign on the ∼150  Mpc scale. On the other hand, if the alternative gravity theory has a large nonlinear term that couples modes on different scales, then the theory would predict large-scale non-Gaussian features in large-scale structure. These are not seen in the distribution of galaxies nor in the distribution of quasars. No proposed alternative gravity theory for dark matter seems to satisfy these constraints.

Precision Metrology Meets Cosmology: Improved Constraints on Ultralight Dark Matter from Atom-Cavity Frequency Comparisons

We conduct frequency comparisons between a state-of-the-art strontium optical lattice clock, a cryogenic crystalline silicon cavity, and a hydrogen maser to set new bounds on the coupling of ultralight dark matter to standard model particles and fields in the mass range of 10^{-16}-10^{-21}  eV. The key advantage of this two-part ratio comparison is the differential sensitivity to time variation of both the fine-structure constant and the electron mass, achieving a substantially improved limit on the moduli of ultralight dark matter, particularly at higher masses than typical atomic spectroscopic results. Furthermore, we demonstrate an extension of the search range to even higher masses by use of dynamical decoupling techniques. These results highlight the importance of using the best-performing atomic clocks for fundamental physics applications, as all-optical timescales are increasingly integrated with, and will eventually supplant, existing microwave timescales.

Search for Composite Dark Matter with Optically Levitated Sensors

Results are reported from a search for a class of composite dark matter models with feeble long-range interactions with normal matter. We search for impulses arising from passing dark matter particles by monitoring the mechanical motion of an optically levitated nanogram mass over the course of several days. Assuming such particles constitute the dominant component of dark matter, this search places upper limits on their interaction with neutrons of α_{n}≤1.2×10^{-7} at 95% confidence for dark matter masses between 1 and 10 TeV and mediator masses m_{ϕ}≤0.1  eV. Because of the large enhancement of the cross section for dark matter to coherently scatter from a nanogram mass (∼10^{29} times that for a single neutron) and the ability to detect momentum transfers as small as ∼200  MeV/c, these results provide sensitivity to certain classes of composite dark matter models that substantially exceeds existing searches, including those employing kilogram- or ton-scale targets. Extensions of these techniques can enable directionally sensitive searches for a broad class of previously inaccessible heavy dark matter candidates.

Explaining the XENON1T Excess with Luminous Dark Matter

We show that the excess in electron recoil events seen by the XENON1T experiment can be explained by a relatively low-mass luminous dark matter candidate. The dark matter scatters inelastically in the detector (or the surrounding rock) to produce a heavier dark state with a ∼2-3  keV mass splitting. This heavier state then decays within the detector, producing a peak in the electron recoil spectrum that is a good fit to the observed excess. We comment on the ability of future direct detection experiments to differentiate this model from other "beyond the standard model" scenarios and from possible tritium backgrounds, including the use of diurnal modulation, multichannel signals, etc., as possible distinguishing features of this scenario.

Filtered Dark Matter at a First Order Phase Transition

We describe a new mechanism of dark matter production. If dark matter particles acquire mass during a first order phase transition, it is energetically unfavorable for them to enter the expanding bubbles. Instead, most of them are reflected and quickly annihilate away. The bubbles eventually merge as the phase transition completes and only the dark matter particles that have entered the bubbles survive to constitute the observed dark matter today. This mechanism can produce dark matter with masses from the TeV scale to above the PeV scale, surpassing the Griest-Kamionkowski bound.

First Germanium-Based Constraints on Sub-MeV Dark Matter with the EDELWEISS Experiment

We present the first Ge-based constraints on sub-MeV/c^{2} dark matter (DM) particles interacting with electrons using a 33.4 g Ge cryogenic detector with a 0.53 electron-hole pair (rms) resolution, operated underground at the Laboratoire Souterrain de Modane. Competitive constraints are set on the DM-electron scattering cross section, as well as on the kinetic mixing parameter of dark photons down to 1  eV/c^{2}. In particular, the most stringent limits are set for dark photon DM in the 6 to 9  eV/c^{2} range. These results demonstrate the high relevance of Ge cryogenic detectors for the search of DM-induced eV-scale electron signals.

Cosmogenic Activation in Double Beta Decay Experiments

Double beta decay is a very rare nuclear process and, therefore, experiments intended to detect it must be operated deep underground and in ultra-low background conditions. Long-lived radioisotopes produced by the previous exposure of materials to cosmic rays on the Earth’s surface or even underground can become problematic for the required sensitivity. Here, the studies developed to quantify and reduce the activation yields in detectors and materials used in the set-up of these experiments will be reviewed, considering target materials like germanium, tellurium and xenon together with other ones commonly used like copper, lead, stainless steel or argon. Calculations following very different approaches and measurements from irradiation experiments using beams or directly cosmic rays will be considered for relevant radioisotopes. The effect of cosmogenic activation in present and future double beta decay projects based on different types of detectors will be analyzed too.

Higgs Boson Emerging from the Dark

We propose a new nonthermal mechanism of dark matter production based on vacuum misalignment. A global X-charge asymmetry is generated at high temperatures, under which both the will-be Higgs boson and the dark matter are charged. At lower energies, the vacuum changes alignment and breaks the U(1)_{X}, leading to the emergence of the Higgs bosonand of a fraction of charge asymmetry stored in the stable dark matter relic. This mechanism can be present in a wide variety of models based on vacuum misalignment, and we demonstrate it in a composite Higgs template model, where all the necessary ingredients are naturally present. A light pseudo-scalar η is always predicted, with interesting implications for cosmology, future supernova observations and exotic Z→γη decays.

Search for Dark Matter Induced Deexcitation of ^{180}Ta^{m}

Weak-scale dark matter particles, in collisions with nuclei, can mediate transitions between different nuclear energy levels. In particular, owing to sizeable momentum exchange, dark matter particles can enable de-excitation of nuclear isomers that are extremely long lived with respect to regular radioactive decays. In this Letter, we utilize data from a past experiment with ^{180}Ta^{m} to search for γ lines that would accompany dark matter induced de-excitation of this isomer. Nonobservation of such transitions above background yields the first direct constraint on the lifetime of ^{180}Ta^{m} against dark matter initiated transitions: T_{1/2}>1.3×10^{14} a at 90% credibility. Using this result, we derive novel constraints on dark matter models with strongly interacting relics and on models with inelastic dark matter particles. Existing constraints are strengthened by this independent new method. The obtained limits are also valid for the standard model γ-decay of ^{180}Ta^{m}.

Directly Detecting Signals from Absorption of Fermionic Dark Matter

We present a new class of direct detection signals; absorption of fermionic dark matter. We enumerate the operators through dimension six which lead to fermionic absorption, study their direct detection prospects, and summarize additional constraints on their suppression scale. Such dark matter is inherently unstable as there is no symmetry which prevents dark matter decays. Nevertheless, we show that fermionic dark matter absorption can be observed in direct detection and neutrino experiments while ensuring consistency with the observed dark matter abundance and required lifetime. For dark matter masses well below the GeV scale, dedicated searches for these signals at current and future experiments can probe orders of magnitude of unexplored parameter space.

Predictions and Outcomes for the Dynamics of Rotating Galaxies

A review is given of a priori predictions made for the dynamics of rotating galaxies. One theory—MOND—has had many predictions corroborated by subsequent observations. While it is sometimes possible to offer post hoc explanations for these observations in terms of dark matter, it is seldom possible to use dark matter to predict the same phenomena.

Thermal Relic Targets with Exponentially Small Couplings

If dark matter was produced in the early Universe by the decoupling of its annihilations into known particles, there is a sharp experimental target for the size of its coupling. We show that if dark matter was produced by inelastic scattering against a lighter particle from the thermal bath, then its coupling can be exponentially smaller than the coupling required for its production from annihilations. As an application, we demonstrate that dark matter produced by inelastic scattering against electrons provides new thermal relic targets for direct detection and fixed target experiments.

Natural Twin Neutralino Dark Matter

Supersymmetric twin Higgs models have a discrete symmetry for which each standard model particle and its supersymmetric partner have a corresponding state that transforms under a mirror standard model gauge group. This framework is able to accommodate the nondiscovery of new particles at the LHC with the naturalness of the electroweak scale. We point out that supersymmetric twin Higgs models also provide a natural dark matter candidate. We investigate the possibility that a twin binolike state is the lightest supersymmetric particle and find that its freeze-out abundance can explain the observed dark matter abundance without fine-tuning the mass spectrum of the theory. Most of the viable parameter space can be probed by future dark matter direct detection experiments, and the LHC searches for staus and Higgsinos which may involve displaced vertices.

Dark Matter Signals from Timing Spectra at Neutrino Experiments

We propose a novel strategy to search for new physics in timing spectra at low-energy neutrino experiments using a pulsed beam, envisioning the situation in which a new particle comes from the decay of its heavier partner with a finite particle width. The timing distribution of events induced by the dark matter (DM) candidate particle scattering at the detector may populate in a relatively narrow range, forming a "resonancelike" shape. Because of this structural feature, the signal may be isolated from the backgrounds, in particular when the backgrounds are uniformly distributed in energy and time. For proof of the principle, we investigate the discovery potential for DM from the decay of a dark photon in the ongoing COHERENT experiment and show the exciting prospects for exploring the associated parameter space with this experiment. We analyze the existing CsI detector data with a timing cut and an energy cut, and we find, for the first time, an excess in the timing distribution that can be explained by such DM. We compare the sensitivity to the kinetic mixing parameter (ε) for current and future COHERENT experiments with the projected limits from LDMX and DUNE.

Cornering Higgsinos Using Soft Displaced Tracks

Higgsino has been intensively searched for in the LHC experiments in recent years. Currently, there is an uncharted region beyond the LEP Higgsino mass limit where the mass splitting between the neutral and charged Higgsinos is around 0.3-1 GeV, which is unexplored by either the soft di-lepton or disappearing track searches. This region is, however, of great importance from a phenomenological point of view, as many supersymmetric models predict such a mass spectrum. In this Letter, we propose a possibility of filling this gap by using a soft microdisplaced track in addition to the monojet event selection, which allows us to discriminate a signature of the charged Higgsino decay from the standard model background. It is found that this new strategy is potentially sensitive to a Higgsino mass of ≲180(250)  GeV at the LHC Run2 (HL-LHC) for a charged-neutral mass splitting of ≃0.5  GeV.

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.

Rucio beyond ATLAS: experiences from Belle II, CMS, DUNE, EISCAT3D, LIGO/VIRGO, SKA, XENON

For many scientific projects, data management is an increasingly complicated challenge. The number of data-intensive instruments generating unprecedented volumes of data is growing and their accompanying workflows are becoming more complex. Their storage and computing resources are heterogeneous and are distributed at numerous geographical locations belonging to different administrative domains and organisations. These locations do not necessarily coincide with the places where data is produced nor where data is stored, analysed by researchers, or archived for safe long-term storage. To fulfil these needs, the data management system Rucio has been developed to allow the high-energy physics experiment ATLAS at LHC to manage its large volumes of data in an efficient and scalable way. But ATLAS is not alone, and several diverse scientific projects have started evaluating, adopting, and adapting the Rucio system for their own needs. As the Rucio community has grown, many improvements have been introduced, customisations have been added, and many bugs have been fixed. Additionally, new dataflows have been investigated and operational experiences have been documented. In this article we collect and compare the common successes, pitfalls, and oddities that arose in the evaluation efforts of multiple diverse experiments, and compare them with the ATLAS experience. This includes the high-energy physics experiments Belle II and CMS, the neutrino experiment DUNE, the scattering radar experiment EISCAT3D, the gravitational wave observatories LIGO and VIRGO, the SKA radio telescope, and the dark matter search experiment XENON.

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.

Light Dark Matter Search with Ionization Signals in XENON1T

We report constraints on light dark matter (DM) models using ionization signals in the XENON1T experiment. We mitigate backgrounds with strong event selections, rather than requiring a scintillation signal, leaving an effective exposure of (22±3) tonne day. Above ∼0.4  keV_{ee}, we observe <1  event/(tonne day keV_{ee}), which is more than 1000 times lower than in similar searches with other detectors. Despite observing a higher rate at lower energies, no DM or CEvNS detection may be claimed because we cannot model all of our backgrounds. We thus exclude new regions in the parameter spaces for DM-nucleus scattering for DM masses m_{χ} within 3-6  GeV/c^{2}, DM-electron scattering for m_{χ}>30  MeV/c^{2}, and absorption of dark photons and axionlike particles for m_{χ} within 0.186-1  keV/c^{2}.

Search for Light Dark Matter Interactions Enhanced by the Migdal Effect or Bremsstrahlung in XENON1T

Direct dark matter detection experiments based on a liquid xenon target are leading the search for dark matter particles with masses above ∼5  GeV/c^{2}, but have limited sensitivity to lighter masses because of the small momentum transfer in dark matter-nucleus elastic scattering. However, there is an irreducible contribution from inelastic processes accompanying the elastic scattering, which leads to the excitation and ionization of the recoiling atom (the Migdal effect) or the emission of a bremsstrahlung photon. In this Letter, we report on a probe of low-mass dark matter with masses down to about 85  MeV/c^{2} by looking for electronic recoils induced by the Migdal effect and bremsstrahlung using data from the XENON1T experiment. Besides the approach of detecting both scintillation and ionization signals, we exploit an approach that uses ionization signals only, which allows for a lower detection threshold. This analysis significantly enhances the sensitivity of XENON1T to light dark matter previously beyond its reach.

Low-Energy Physics Reach of Xenon Detectors for Nuclear-Recoil-Based Dark Matter and Neutrino Experiments

Dual-phase xenon detectors lead the search for keV-scale nuclear recoil signals expected from the scattering of weakly interacting massive particle (WIMP) dark matter, and can potentially be used to study the coherent nuclear scattering of MeV-scale neutrinos. New capabilities of such experiments can be enabled by extending their nuclear recoil searches down to the lowest measurable energy. The response of the liquid xenon target medium to nuclear recoils, however, is not well characterized below a few keV, leading to large uncertainties in projected sensitivities. In this work, we report a new measurement of ionization signals from nuclear recoils in liquid xenon down to the lowest energy reported to date. At 0.3 keV, we find that the average recoil produces approximately one ionization electron; this is the first measurement of nuclear recoil signals at the single-ionization-electron level, approaching the physical limit of liquid xenon ionization detectors. We discuss the implications of these measurements on the physics reach of xenon detectors for nuclear-recoil-based WIMP dark matter searches and the detection of coherent elastic neutrino-nucleus scattering.

Search for Light Weakly-Interacting-Massive-Particle Dark Matter by Annual Modulation Analysis with a Point-Contact Germanium Detector at the China Jinping Underground Laboratory

We present results on light weakly interacting massive particle (WIMP) searches with annual modulation (AM) analysis on data from a 1-kg mass p-type point-contact germanium detector of the CDEX-1B experiment at the China Jinping Underground Laboratory. Datasets with a total live time of 3.2 yr within a 4.2-yr span are analyzed with analysis threshold of 250 eVee. Limits on WIMP-nucleus (χ-N) spin-independent cross sections as function of WIMP mass (m_{χ}) at 90% confidence level (C.L.) are derived using the dark matter halo model. Within the context of the standard halo model, the 90% C.L. allowed regions implied by the DAMA/LIBRA and CoGeNT AM-based analysis are excluded at >99.99% and 98% C.L., respectively. These results correspond to the best sensitivity at m_{χ}<6  GeV/c^{2} among WIMP AM measurements to date.

Constraints on Light Dark Matter Particles Interacting with Electrons from DAMIC at SNOLAB

We report direct-detection constraints on light dark matter particles interacting with electrons. The results are based on a method that exploits the extremely low levels of leakage current of the DAMIC detector at SNOLAB of 2-6×10^{-22}  A cm^{-2}. We evaluate the charge distribution of pixels that collect <10e^{-} for contributions beyond the leakage current that may be attributed to dark matter interactions. Constraints are placed on so-far unexplored parameter space for dark matter masses between 0.6 and 100  MeV c^{-2}. We also present new constraints on hidden-photon dark matter with masses in the range 1.2-30  eV c^{-2}.

Constraints on Spin-Independent Nucleus Scattering with sub-GeV Weakly Interacting Massive Particle Dark Matter from the CDEX-1B Experiment at the China Jinping Underground Laboratory

We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses (m_{χ}) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg day exposure and 250 eVee threshold for AM analysis. The sensitive windows in m_{χ} are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on σ_{χN}^{SI} at 90% confidence level are derived as 2×10^{-32}∼7×10^{-35}  cm^{2} for TI analysis at m_{χ}∼50-180  MeV/c^{2}, and 3×10^{-32}∼9×10^{-38}  cm^{2} for AM analysis at m_{χ}∼75  MeV/c^{2}-3.0  GeV/c^{2}.