Direct Weakly Interacting Massive Particles Research Articles

Direct WIMP detection rates for transitions in isomeric nuclei

The direct detection of dark matter constituents, in particular the weakly interacting massive particles (WIMPs), is central to particle physics and cosmology. In this paper we study WIMP induced transitions from isomeric nuclear states for two possible isomeric candidates: Ta180 and Ho166. The experimental setup, which can measure the possible decay of Ta180 induced by WIMPs, was proposed. The corresponding estimates of the half-life of Ta180 are given in the sense that the WIMP-nucleon interaction can be interpreted as ordinary radioactive decay.

Can we overcome the neutrino floor at high masses?

The neutrino floor is a barrier in the parameter space of weakly interacting massive particles (WIMPs) below which discovery is impeded due to an almost irreducible background of neutrinos. Directional gas time projection chambers could discriminate against solar neutrinos, relevant for WIMP masses $\lesssim$10 GeV. At higher masses $\gtrsim$100 GeV the floor is set by the background of atmospheric neutrinos. Probing below this part of the floor would require very large target exposures. Since gas-based detectors would be prohibitively large at this scale, we instead reevaluate the prospects for liquid noble experiments to probe below the neutrino floor. We combine all potential methods of subtracting the neutrino background to determine how much of this difficult to reach, but well-motivated, parameter space it is feasible to reach. Most notably, we quantify whether a proposed directional signal in xenon and argon experiments called "columnar recombination" can help in this task. We find that even if the strength of this effect is amplified beyond current experimental results, the quantity of directional information contained in the recombination signal is too low to realistically discriminate against the atmospheric neutrino background. Instead, benefiting from the refined measurements of neutrino fluxes by experiments such as DUNE and JUNO will be the most practical means to push direct WIMP searches below the neutrino floor. For an ultimate global coordination of xenon and argon experiments, we show that the neutrino floor is a surmountable barrier. The direct detection of 100 GeV-scale supersymmetric WIMPs may, eventually, be within reach.

Neutralino dark matter in scenarios with early matter domination

We investigate the production of neutralino dark matter in a cosmological scenario featuring an early matter dominated era ending at a relatively low reheating temperature. In such scenarios different production mechanisms of weakly interacting massive particles (WIMPs), besides the well-studied thermal production, can be important. This opens up new regions of parameter space where the lightest neutralino, as the best-known supersymmetric (SUSY) WIMP, obtains the required relic abundance. Many of these new sets of parameters are also compatible with current limits from colliders as well as direct and indirect WIMP searches. In particular, in standard cosmology bino-like neutralinos, which emerge naturally as lightest neutralino in many models, can have the desired relic density only in some finetuned regions of parameter space where the effective annihilation cross section is enhanced by co-annihilation or an s-channel pole. In contrast, if the energy density of the universe was dominated by long-lived PeV-scale particles (e.g. moduli or Polonyi fields), bino-like neutralinos can obtain the required relic density over wide regions of supersymmetric parameter space. We identify the interesting ranges of mass and decay properties of the heavy long-lived particles, carefully treating the evolution of the temperature of the thermal background.

Anatomy of Eddington-like inversion methods in the context of dark matter searches

Irrespective of the dark matter (DM) candidate, several potentially observable signatures derive from the velocity distribution of DM in halos, in particular in the Milky Way (MW) halo. Examples include direct searches for weakly-interacting massive particles (WIMPs), p-wave suppressed or Sommerfeld-enhanced annihilation signals, microlensing events of primordial black holes (PBHs), etc. Most current predictions are based on the Maxwellian approximation which is not only theoretically inconsistent in bounded systems, but also not supported by cosmological simulations. A more consistent method sometimes used in calculations for direct WIMP searches relies on the so-called Eddington inversion method, which relates the DM phase-space distribution function (DF) to its mass density profile and the total gravitational potential of the system. Originally built upon the isotropy assumption, this method can be extended to anisotropic systems. We investigate these inversion methods in the context of Galactic DM searches, motivated by the fact that the MW is a strongly constrained system, and should be even more so with the ongoing Gaia survey. We still draw conclusions that apply to the general case. In particular, we illustrate how neglecting the radial boundary of the DM halo leads to theoretical inconsistencies. We also show that several realistic configurations of the DM halo and the MW baryonic content entail ill-defined DFs, significantly restricting the configuration space over which these inversion methods can apply. We propose consistent solutions to these issues. Finally, we compute several observables inferred from constrained Galactic mass models relevant to DM searches (WIMPs or PBHs), e.g. moments and inverse moments of the DM speed and relative speed distributions.

Evaluation of neutron background in cryogenic Germanium target for WIMP direct detection when using reactor neutrino detector as neutron veto

Abstract A direct WIMP (Weakly Interacting Massive Particle) detector with a neutron veto system is designed to better reject neutrons. An experimental configuration is studied in the present paper: 984 Ge modules are placed inside a reactor neutrino detector. In order to discriminate between nuclear and electron recoil, both ionization and heat signatures are measured using cryogenic germanium detectors in this detection. The neutrino detector is used as a neutron veto device. The neutron background for the experimental design has been estimated using the Geant4 simulation. The results show that the neutron background can decrease to O(0.01) events per year per tonne of high purity Germanium. We calculate the sensitivity to spin-independent WIMP–nucleon elastic scattering. An exposure of one tonne × year could reach a cross-section of about 2×10−11 pb.

Dark Coulomb binding of heavy neutrinos of fourth family

Direct dark matter searches put severe constraints on the weakly interacting massive particles (WIMPs). These constraints cause serious troubles for the model of stable neutrino of fourth generation with mass around 50[Formula: see text]GeV. Though the calculations of primordial abundance of these particles make them in the charge symmetric case a sparse subdominant component of the modern dark matter, their presence in the universe would exceed the current upper limits by several orders of the magnitude. However, if quarks and leptons of fourth generation possess their own Coulomb-like [Formula: see text]-interaction, recombination of pairs of heavy neutrinos and antineutrinos and their annihilation in the “neutrinium” atoms can play important role in their cosmological evolution, reducing their modern abundance far below the experimental upper limits. The model of stable fourth generation assumes that the dominant part of dark matter is explained by excessive [Formula: see text] antiquarks, forming [Formula: see text] charged clusters, bound with primordial helium in nuclear-interacting O-helium (OHe) dark atoms. The [Formula: see text] charge conservation implies generation of the same excess of fourth generation neutrinos, potentially dangerous WIMP component of this scenario. We show that due to [Formula: see text]-interaction recombination of fourth neutrinos with OHe hides these WIMPs from direct WIMP searches, leaving the negligible fraction of free neutrinos, what makes their existence compatible with the experimental constraints.

Theoretical direct WIMP detection rates for transitions to the first excited state inKr83

The recent WMAP and Planck data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Many extensions of the standard model provide dark matter candidates, in particular Weakly Interacting Massive Particles (WIMPs). Thus the direct dark matter detection is central to particle physics and cosmology. Most of the research on this issue has hitherto focused on the detection of the recoiling nucleus. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Examples considered previously were the first excited states of $^{127}$I and $^{129}$Xe. We examine here $^{83}$Kr, which offers some kinematical advantages and is currently considered as a possible target. We find appreciable branching ratios for the inelastic scattering mediated by the spin cross sections, with an inelastic event rate of $4.4\times 10^{-4}$kg$^{-1}$d$^{-1}$. So, the extra signature of the gamma ray following the de-excitation of these states can, in principle, be exploited experimentally. A brief discussion of the experimental feasibility is given

Evaluation of the neutron background in CsI target for WIMP direct detection when using a reactor neutrino detector as a neutron veto system

A direct WIMP (Weakly Interacting Massive Particle) detector with a neutron veto system is designed to better reject neutrons. An experimental configuration is studied in the present paper: a WIMP detectors with CsI(Na) target is placed inside a reactor neutrino detector. The neutrino detector is used as a neutron veto device. The neutron background for the experimental design has been estimated using the Geant4 simulation. The results show that the neutron background can decrease to O(0.01) events per year per tonne of CsI(Na). We calculate the sensitivity to spin-independent WIMP-nucleon elastic scattering. An exposure of one tonne $\times$ year could reach a cross-section of about 3$\times$$10^{-11}$ pb.

DarkSide-50, a background free experiment for dark matter searches

The existence of dark matter is inferred from gravitational effects, but its nature remains a deep mystery. One possibility, motivated by considerations in elementary particle physics, is that dark matter consists of elementary particles, such as the hypothesized Weakly Interacting Massive Particles (WIMPs), with mass ∼ 100 GeV and cross-section ∼ 10−47 cm2, that can be gravitationally trapped inside our galaxy and revealed by their scattering on nuclei. It should be possible to detect WIMPs directly, as the orbital motion of the WIMPs composing the dark matter halo pervading the galaxy should result in WIMP-nucleus collisions of sufficient energy to be observable in the laboratory. The DarkSide-50 experiment is a direct WIMP search using a Liquid Argon Time Projection Chamber (LAr-TPC) with an active mass of 50 kg with a high sensitivity and an ultra-low background detector.

Evaluation of the neutron background in an HPGe target for WIMP direct detection when using a reactor neutrino detector as a neutron veto system

A direct WIMP (Weakly Interacting Massive Particle) detector with a neutron veto system is designed to better reject neutrons. An experimental configuration is studied in the present paper: 984 Ge modules are placed inside a reactor neutrino detector. In order to discriminate between nuclear and electron recoil, both ionization and heat signatures are measured using cryogenic germanium detectors in this detection. The neutrino detector is used as a neutron veto device.The neutron background for the experimental design has been estimated using the Geant4 simulation. The results show that the neutron background can decrease to O(0.01) events per year per tonne of high purity Germanium. We calculate the sensitivity to spin-independent WIMP-nucleon elastic scattering. An exposure of one tonne $\times$ year could reach a cross-section of about 2$\times$$10^{-11}$ pb.

Theoretical direct WIMP detection rates for inelastic scattering to excited states

The recent WMAP and Planck data have confirmed that exotic dark matter together with the vacuum energy (cosmological constant) dominate in the flat Universe. Many extensions of the standard model provide dark matter candidates, in particular Weakly Interacting Massive Particles (WIMPs). Thus the direct dark matter detection is central to particle physics and cosmology. Most of the research on this issue has hitherto focused on the detection of the recoiling nucleus. In this paper we study transitions to the excited states, possible in some nuclei, which have sufficiently low lying excited states. Good examples are the first excited states of 127I and 129Xe. We find appreciable branching ratios for the inelastic scattering mediated by the spin cross sections. So, in principle, the extra signature of the gamma ray following the de-excitation of these states can, in principle, be exploited experimentally.

Evaluation of the neutron background in a direct WIMP detector with neutron vetosystem based on Gd-doped liquid scintillator

A direct WIMP (Weakly Interacting Massive Particle) detector with aneutron veto system is designed to better reject neutrons. Twoexperimental configurations are studied in the present paper: one isfor an Xe detector enclosed in a Gd-loaded scintillator and theother one is for an Xe detector placed inside a reactor neutrinodetector. The Gd-doped liquid scintillator (or the neutrinodetector) is used as a neutron veto device. The neutron backgroundsfor the two experimental designs have been estimated using Geant4simulations. The results show that the neutron backgrounds candecrease to O(0.1) events per year per tonne of liquid Xenon. Wecalculate the sensitivities to spin-independent WIMP-nucleon elasticscattering. An exposure of one tonne × year could reach across-section of about 6 × 10−11 pb.

Shedding light on the dark sector with direct WIMP production

A weakly interacting massive particle (WIMP) provides an attractive dark matter candidate, and should be within reach of the next generation of high-energy colliders. We consider the process of direct WIMP pair-production, accompanied by an initial-state radiation photon, in electron–positron collisions at the proposed International Linear Collider (ILC). We present a parametrization of the differential cross section for this process which conveniently separates the model-independent information provided by cosmology from the model-dependent inputs from particle physics. As an application, we consider two simple models, one supersymmetric and another of the ‘universal extra dimensions’ (UED) type. The discovery reach of the ILC and the expected precision of parameter measurements are studied in each model. In addition, for each of the two examples, we also investigate the ability of the ILC to distinguish between the two models through a shape-discrimination analysis of the photon energy spectrum. We show that with sufficient beam polarization the alternative model interpretation can be ruled out in a large part of the relevant parameter space.

Dark matter and the CACTUS gamma-ray excess from Draco

The CACTUS atmospheric Cherenkov telescope collaboration recently reporteda gamma-ray excess from the Draco dwarf spheroidal galaxy. Draco features avery low gas content and a large mass-to-light ratio, suggesting as a possibleexplanation annihilation of weakly interacting massive particles (WIMPs) in theDraco dark-matter halo. We show that with improved angular resolution, futuremeasurements can determine whether the halo is cored or cuspy, as well as its scale radius.We find the relevant WIMP masses and annihilation cross sections and showthat supersymmetric models can account for the required gamma-ray flux. Theannihilation cross section range is found to be not compatible with a standard thermalrelic dark-matter production. We compute for these supersymmetric models theresulting Draco gamma-ray flux in the GLAST energy range and the rates for directneutralino detection and for the flux of neutrinos from neutralino annihilationin the Sun. We also discuss the possibility that the bulk of the signal detectedby CACTUS comes from direct WIMP annihilation to two photons and pointout that a decaying-dark-matter scenario for Draco is not compatible with thegamma-ray flux from the Galactic centre and in the diffuse gamma-ray background.

CRESST-II: dark matter search with scintillating absorbers

In the CRESST-II experiment, scintillating CaWO4 crystals are used as absorbers for direct WIMP (weakly interacting massive particles) detection. Nuclear recoils can be discriminated against electron recoils by measuring phonons and scintillation light simultaneously. The absorber crystal and the silicon light detector are read out by tungsten superconducting phase transition thermometers (W-SPTs). Results on the sensitivity of the phonon and the light channel, radiopurity, the scintillation properties of CaWO4, and on the WIMP sensitivity are presented.

CRESST Detectors for Nonbaryonic Cold Dark Matter Particles

The CRESST experiment is set up for the direct detection of Weakly Interacting Massive Particles (WIMPs) which our Galactic dark matter halo possibly consists of. the employed detection method is elastic scattering by nuclei. the recoiling nucleus deposits most of its energy in the form of lattice vibrations in the detector. Cooling the detector to very low temperatures (mK) enhances the temperature rise due to the energy deposition. the crucial parameter for direct WIMP searches is the sensitivity to the WIMP interaction cross section in a certain range of possible WIMP masses. CRESST is now sensitive enough to explore the parameter space predicted by supersymmetric models.

Sensitivity plots for WIMP direct detection using the annual modulation signature

Annual modulation due to the Earth's motion around the Sun is a well-known signature of the expected weakly interacting massive particle (WIMP) signal induced in a solid state underground detector. In the present paper, we discuss the prospects of this technique on statistical grounds, introducing annual-modulation sensitivity plots for the WIMP–nucleon scalar cross-section for different materials and experimental conditions. The highest sensitivity to modulation is found in the WIMP mass interval 10≲ m W≲130 GeV, the actual upper limit depends on the choice of the astrophysical parameters, while the lowest values of the explorable WIMP–nucleon elastic cross-sections fall in most cases within one order of magnitude of the sensitivities of the present direct detection WIMP searches.