Haut PDF Dark Matter Direct Detection using Cryogenic Detectors

Dark Matter Direct Detection using Cryogenic Detectors

Dark Matter Direct Detection using Cryogenic Detectors

picobarn, and therefore ∼ 4 orders of magnitude above that of the discrimi- nating cryogenic experiments. 8.3 The Tokyo LiF bolometer experiment The Tokyo group [72,114] has used lithium fluoride bolometers at a temper- ature of ∼ 10 mK to take advantage of the excellent axial WIMP-nucleon cross-sections of the fluoride nucleus [115] and, to a lesser extent, of the lithium nucleus. After an initial experiment in a shallow laboratory, close to surface, which used a set of 8 × 21 g LiF detectors [72], a second experi- ment was performed in the Kamiokande underground laboratory to benefit from the reduced cosmic-ray induced background [114]. Surprisingly enough, the Kamiokande measurements have not led until now to improvements in background performances and the sensitivity reached by the Tokyo LiF de- tectors still falls short by nearly three orders of magnitude of the sensitiv- ity required to sample the most optimistic SUSY models. While this ex- periment provides an illustration of the fact that a large variety of target materials can be used in bolometers, it also confirms that most of these detectors, lacking background discrimination capabilities, are unable to pro- vide sensitivities comparable to indirect detection experiments such as Su- perkamiokande [116] and Amanda [117]. These experiments, searching for high-energy neutrinos from the core of the Sun, provide much more stringent constraints for spin-dependent WIMP-nucleon couplings than those obtained by these non-discriminating experiments [118].
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The Direct Detection of Boosted Dark Matter at High Energies and PeV events at IceCube

The Direct Detection of Boosted Dark Matter at High Energies and PeV events at IceCube

Abstract. We study the possibility of detecting dark matter directly via a small but energetic component that is allowed within present-day constraints. Drawing closely upon the fact that neutral current neutrino nucleon interactions are indistinguishable from DM-nucleon interactions at low energies, we extend this feature to high energies for a small, non-thermal but highly energetic population of DM particle χ, created via the decay of a significantly more massive and long-lived non-thermal relic φ, which forms the bulk of DM. If χ interacts with nucleons, its cross-section, like the neutrino-nucleus coherent cross-section, can rise sharply with energy leading to deep inelastic scattering, similar to neutral current neutrino-nucleon interactions at high energies. Thus, its direct detection may be possible via cascades in very large neutrino detectors. As a specific example, we apply this notion to the recently reported three ultra-high energy PeV cascade events clustered around 1 − 2 PeV at IceCube (IC). We discuss the features which may help discriminate this scenario from one in which only astrophysical neutrinos constitute the event sample in detectors like IC.
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Composite dark matter and direct-search experiments

Composite dark matter and direct-search experiments

naive way in underground detectors. To go further with this idea, one could even imagine that dark particles are not elementary but consist of structures made of exotic particles, that we could generically call “composite dark matter”. This com- posite dark matter could either saturate the dark matter density, or be reduced to a fraction of it, the one which produces the signals of direct detection, while the rest would be made of inert particles that act like CDM without producing any recoil, i.e. a particular case of WIMPs that do not interact with standard particles except gravitationally. Of course, we can expect that, if such composite structures exist, they interact with each other and form a kind of self-interacting dark matter which evolves in a complex dark sector with a rich phenomenology and which has common characteristics with ours. Actually, self-interacting dark matter can pro- vide a solution to some small-scale problems of CDM, such as the core/cusp [29, 30] and the missing-satellite problems. It is a viable candidate if it represents only a subdominant part of dark matter, but its self-interactions should be reduced in the case where it is dominant in order to be consistent with the stringent constraints on self-interacting dark matter [31, 32, 33, 34, 35]. The models that will be presented in this work present all these features and all aim at solving the discrepancies between direct-search experiments when they are interpreted in terms of WIMPs.
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Status and Perspectives of Direct Dark Matter Searches

Status and Perspectives of Direct Dark Matter Searches

6. Conclusions WIMP direct detection experiments are finally reaching sensitivities allow- ing to sample SUSY models compatible with accelerator constraints. The first WIMP candidate proposed in 2000 by the DAMA experiment is now clearly excluded by the EDELWEISS result, without any background sub- traction and independently of galactic WIMP models unless unconventional interaction models are used. Over the next few years, a second generation of discriminating experiments, CDMS–II, EDELWEISS–II, CRESST–II and ZEPLIN–II, using mass targets in the 10-30 kg range, intend to reach the
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Complementarity of dark matter detectors in light of the neutrino background

Complementarity of dark matter detectors in light of the neutrino background

As the exposures of direct dark matter detection experi- ments continue to improve, they will soon have enough sensitivity to detect neutrinos from several astrophysical sources such as the Sun, the atmosphere, and diffuse supernovae [4 –9] . For example, a 1 keV threshold Xe based experiment with a 1 ton-year exposure will detect about 100 8 B solar neutrino events via coherent neutrino- nucleus scattering (CNS). In fact for some WIMP masses, such neutrino backgrounds can almost perfectly mimic a WIMP signal. It has been shown in Ref. [10] that the CNS background leads to a strong reduction of the discovery potential of upcoming experiments. Therefore, though neither coherent neutrino scattering nor the WIMP-nucleus interaction have conclusively been observed yet, the search for discrimination methods to disentangle WIMPs from neutrino events is a necessity.
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Tools for model-independent bounds in direct dark matter searches

Tools for model-independent bounds in direct dark matter searches

4.2 Cdms-Ge The Cryogenic Dark Matter Search (Cdms II) experiment is located at the Soudan Un- derground Laboratory in Minnesota. 19 Germanium and 11 Silicon detectors measure the energy deposited by incident particles in the form of phonons and ionization. The ratio between these two signals provides event-by-event rejection of electron recoils produced by incident electrons and photons. Due to the reduced ionization collection in the external part of the detectors, electron recoils occurring near the surface (‘surface events’) are more likely to be misidentified as nuclear recoils; however, these events can be discriminated and rejected using phonon pulse timing, further lowering the background from electromagnetic events.
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Searching for dark matter with superheated liquid detectors

Searching for dark matter with superheated liquid detectors

One of the most prominent questions in the fields of particle physics and cosmol- ogy is the nature of dark matter which comprises 85% of the total mass of the universe. The PICASSO and PICO experiments are both direct detection experiments situated at SNOLAB that use the superheated liquid or bubble chamber technique to search for dark matter. The PICASSO collaboration pioneered the use of this technique for dark mat- ter searches, and moreover, discovered an important background suppression feature: the acoustic alpha-neutron discrimination. The last PICASSO result was published in 2017 and still holds to this day the best spin-dependent cross-section limit of 7 ×10 −2 pb (90% C.L.) for weakly interacting dark matter candidates (WIMPs) with a mass of 4 GeV/c 2 [1]. Since the merger of PICASSO and COUPP into PICO, PICO holds the world best limit on WIMP cross sections with the most stringent spin-dependent limit of 2.5 ×10 −5 pb (90% C.L) at 25 GeV/c 2 set by the recent PICO60 detector result [2]. The PICO collaboration is currently building a new detector called PICO40L with a sig- nificantly improved design which will allow to substantially decrease the neutron back- ground by a factor of ∼50, and pave the way forward for the next stage, PICO500, which will contain approximately 500L of superheated liquid.
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Broadband and Resonant Approaches to Axion Dark Matter Detection

Broadband and Resonant Approaches to Axion Dark Matter Detection

Our proposed design is shown schematically in Fig. 1 . The static magnetic field B 0 is generated by a constant current in a superconducting wire wrapping a toroid, and the axion effective current is detected with a superconduct- ing pickup loop in the toroid hole. In the absence of axion DM (or noise), there is no magnetic flux through the pickup loop. With axion DM, there will be an oscillating magnetic flux through the pickup loop proportional to p ffiffiffiffiffiffiffiffiffi ρDM . This design is inspired by cryogenic current comparators (CCCs) [21] , which are used for measuring real currents. The key difference here is the static external field B 0 , which generates an effective electric current in the presence of axion DM instead of the real current in the case of the CCC. In a real implementation of both designs, the signal flux is actually sourced by a Meissner current which returns along the outside surface of a gapped toroid. The size of the gap is not crucial for our analysis, but must be sufficiently large that parasitic capacitance effects do not generate a displacement current, which might shunt the Meissner return current and reduce the induced signal B field. For wires of diameter 1 mm and a meter-sized toroid, a gap of a few millimeters allows unscreened currents up to the frequency at which the magnetoquasistatic approximation breaks down and displacement currents are unavoidable. In what follows, we will estimate our sensitivity using the axion effective current which is correct up to Oð1Þ geometric factors.
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Atomic ionization by sterile-to-active neutrino conversion and constraints on dark matter sterile neutrinos with germanium detectors

Atomic ionization by sterile-to-active neutrino conversion and constraints on dark matter sterile neutrinos with germanium detectors

The transition magnetic moment of a sterile neutrino can give rise to its conversion to an active neutrino through radiative decay or nonstandard interaction (NSI) with matter. For sterile neutrinos of keV-mass as dark matter candidates, their decay signals are actively searched for in cosmic x-ray spectra. In this work, we consider the NSI that leads to atomic ionization, which can be detected by direct dark matter experiments. It is found that this inelastic scattering process for a nonrelativistic sterile neutrino has a pronounced enhancement in the differential cross section at energy transfer about half of its mass, manifesting experimentally as peaks in the measurable energy spectra. The enhancement effects gradually smear out as the sterile neutrino becomes relativistic. Using data taken with low-threshold low-background germanium detectors, constraints on sterile neutrino mass and its transition magnetic moment are derived and compared with those from astrophysical observations.
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Neutralino Dark Matter beyond CMSSM Universality

Neutralino Dark Matter beyond CMSSM Universality

large neutralino annihilation cross section σ A χ−χ (important for its relic density and for indirect detection) and to large neutralino–proton scalar and spin dependent elastic cross sections (important for direct and indirect detection). In this paper, using the same tools as previously [6, 8], we shall relax some universality hypotheses and examine whether more favourable models for relic density and detections (both direct and neutrino telescopes) can be found, and establish that models detectable by neutrino telescopes are more generic than the “focus point” region of a typical (m 0 , m 1/2 ) CMSSM plane, offering a less constrained framework for detection. We
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Study of the single electron charge signals in the XENON100 direct Dark Matter search experiment

Study of the single electron charge signals in the XENON100 direct Dark Matter search experiment

been recently assembled: the DarkSide experiment [95] in LNGS and the ArDM [96] experiment in Canfranc, and have started to acquire data for dark matter seach. Argon single phase detectors The detection process in single phase noble gas chamber is similar to dual phase, with the exception that no drift field is applied. As a consequence, all the electrons released by the ion- isation of atoms during the nuclear recoil will recombine. As for dual phase experiment, two excited states of the argon atoms will be produced: the singlet and triplet state. Each of them will have its own relaxation time. An advantage of the argon with respect to xenon is that the time difference between the two relaxation times is three order times larger for the former noble gas than for the latter, leading to a clear second scintillation signal few micro-seconds after the first one, such as presented in Section 2.3.3.1. Moreover, the two excited states will be created with different proportion for electronic and nuclear recoils. As a results the proportion between these two scintillation signals that will be used for background rejection. Thus, in order to maxi- mize the light collection, single phase noble gas chambers have usually a spherical geometry, with Photo-Multipliers Tubes (PMTs) installed all around, since scintillation is in this case the only one available signal.
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Coherent neutrino scattering in dark matter detectors

Coherent neutrino scattering in dark matter detectors

A. Detection at a ton-scale dark matter experiment Next, we consider one of the nuclear targets mentioned above ( 76 Ge) in more detail. GEODM is a proposed ton- scale dark matter detector [ 27 ] based on the cryogenic Ge crystal technology used in the CDMS experiment [ 31 ]. The target design for GEODM is an array of 300  5 kg Ge crystals operated at 40 mK with a total target mass of 1500 kg. Interaction events in an individual crystal pro- duce populations of athermal phonons and electron-hole pairs which are measured by various phonon and ionization sensors lithographically patterned on the crystal surfaces. The ratio of ionization to phonon signals for an event is a powerful discriminator between electron and nuclear re- coils. The signals also enable precise determination of the position and energy of each event, which allow volume and energy cuts. This information is used to set the number of electron recoils that can pass the cuts and pose as nuclear recoils. This electron recoil ‘‘leakage’’ into the nuclear recoil band constitutes one source of background events. There is also a background from muon- and radiogenic- induced neutrons, which is controlled through the use of radio-pure materials and passive and active shields to be <0:15 events=ton=year.
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Dark matter effective field theory scattering in direct detection experiments

Dark matter effective field theory scattering in direct detection experiments

To examine the effects of the different possible interactions for experiments with similar fiducial masses, we also plot the event rate per time per target mass (Fig. 8 , bottom). Here, we see that both Ge and Si SuperCDMS detectors operating in high-voltage mode are more sensitive to low-mass WIMPs because of their lower thresholds. In particular, the germanium high- voltage rate per kg day (light blue) is nearly an order of magnitude larger than the standard germanium iZIP rate (blue) for certain operators. For higher masses, the rates for xenon (black) and germanium are comparable within an order of magnitude, but the nuclear properties of silicon (red) make it less sensitive to these interactions. In addition, SuperCDMS Ge sees a modest enhancement to the overall event rate at high WIMP masses where the distribution of events extends beyond the assumed 30 keV nr upper limit for LZ. This effect is most promi- nent for operators such as O 3 and O 15 , which have a q 2 dependence that suppresses the rate at low energies, though it is not enough to overcome the effects of LZ ’s larger target mass in the total number of events.
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High Purity Germanium: from gamma-ray detection to dark matter Subterranean detectors

High Purity Germanium: from gamma-ray detection to dark matter Subterranean detectors

6. Conclusion This short review provides an overview of HPGe detectors and their applications in physics [23] [45] and outside it. The future of such detectors depends on the availability of other materials that would match the resolution performance of HPGe at 77K, while operating at room temperature. Segmentation of the detectors provides a way to reduce carrier collection lengths and hence to mitigate the effects of electrically active deep defects. With integrated microelectronics the noise can be as low as a few tens of electrons. With on detectors CMOS chips and low capacitance detectors the electronic noise can be reduced to less than 100 e-h pairs. With equal to 4.5 eV (GaAs,CdTe) , this corresponds to a resolution of the order of 450 eV. This could also be applied to HPGe detectors that are being used for double beta decay or Dark Matter experiments. The multi-electrode scheme that is implemented in EDELWEISS III [46] is a first step towards a time-projection chamber HPGe detector allowing an improved discrimination ability. Each electrode could be a separate channel, which would be easy for the detector operated at low field and low voltage. It seems clear that the use in more routine applications such as for instance high- precision radioactive material characterization and radioactive material tracing to avoid nuclear dissemination will remain a field where HPGe is the most competitive, despite the need for LN2 cryogenic installations. Development of cryogenic cooling fridges will eliminate this specific constraint. In scientific applications, HPGe, being one of the chemically purest materials ever fabricated, will remain to be needed.
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Effective theory of self-interacting dark matter

Effective theory of self-interacting dark matter

These features hint at a possible link between the cosmological properties of dm and the mechanism for electroweak symmetry breaking. In principle, wimp annihilations should still occur today in dense regions of our galaxy. The potential for this type of indirect detection has gained attention recently due to possible anomalies in the positron fluxes measured by pamela [1], Fermi [2] and ams-02 [3], and the gamma ray spectrum measured by Fermi [4–8]. Such signals, however, require the total wimp annihilation cross section to be well in excess of the thermal value. Nevertheless, there are mechanisms to boost the annihilation rate to the level of experimental sensitivity without spoiling the relic abundance. One possibility is that dm has long range self-interactions mediated by a light force carrier. If this exchange of particles produces an attractive self-interaction, it can e↵ectively increase the annihilation cross section because of Sommerfeld enhancement or resonance scattering [9–15]. The annihilation cross section is thus enhanced by a boost factor, S 0 , with S 1, where 0 is the
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Dark matter dynamics in Abell 3827: new data consistent with standard cold dark matter

Dark matter dynamics in Abell 3827: new data consistent with standard cold dark matter

Accepted —. Received —; in original form 16 August 2017. ABSTRACT We present integral field spectroscopy of galaxy cluster Abell 3827, using ALMA and VLT/MUSE. It reveals an unusual configuration of strong gravitational lensing in the cluster core, with at least seven lensed images of a single background spiral galaxy. Lens modelling based on HST imaging had suggested that the dark matter associated with one of the cluster’s central galaxies may be offset. The new spectro- scopic data enable better subtraction of foreground light, and better identification of multiple background images. The inferred distribution of dark matter is consistent with being centered on the galaxies, as expected by ΛCDM. Each galaxy’s dark mat- ter also appears to be symmetric. Whilst we do not find an offset between mass and light (suggestive of self-interacting dark matter) as previously reported, the numeri- cal simulations that have been performed to calibrate Abell 3827 indicate that offsets and asymmetry are still worth looking for in collisions with particular geometries. Meanwhile, ALMA proves exceptionally useful for strong lens image identifications. Key words: dark matter — astroparticle physics — galaxies: clusters: individual: Abell 3827 — gravitational lensing: strong
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About dark matter and gravitation

About dark matter and gravitation

4 More detailed considerations about spiral galaxies and clus- ters. 4.1 About galaxies. A first obvious remark is that we do not have (and probably will never have) any tool to study the global dynamical evolution of a given galaxy, including our milky way. Local considera- tions about speed distribution at a given time (or studied during one century, which is about the same compared to the time unit of 10 8 years corresponding to the minimal time to wait before anything significative may happen) do not give any global information on the dynam- ics. So to guess the dynamics, we need to compare different galaxies, and to bet that their dynamics are comparable, which is not at all a certitude, especially considering the previously recalled limits of our observation span. The observations of Vera Rubin, her colleagues and the followers, led to think that a halo of exotic dark matter surrounds all galaxies (or at least spiral galaxies) until the discovery of two galaxies for which this hypothesis is not necessary (cf.e.g. https://earthsky.org/space/galaxies-lacking-dark-matter-df2-udg). The conclusion of some specialists, against the most elementary common sense, is that exotic dark matter exists, because this absence contradicts MOND theory which they consider as the sole alternative solution. I would like to emphasize here that in all sciences except mathematics, each effect has (and will keep forever) an infinity of possible causes, for two reasons:
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Crack detection in crystalline silicon solar cells using dark-field imaging

Crack detection in crystalline silicon solar cells using dark-field imaging

State-of-the-art technologies for crack detection in silicon materials include: photoluminescence (PL) [9], optical transmission [10,11], infrared (IR) lock-in thermography (LIT) [12], scanning acoustic microscopy (SAM) [13], and dark-field IR scattering [14]. Although all these techniques are suitable for detecting cracks within the wafer, they have several disadvantages for detecting edge cracks; especially cracks with less than a few millimetres in length. In particular, PL has difficulty detecting edge cracks since the technique is based on measuring the reduction in minority carrier lifetimes, yet at early stages in cell fabrication, the edges themselves reduce the local lifetime [9]. Optical transmission is challenging because it relies on reduced transmission when a crack is present; thus, the method inherently has a low signal-to-noise ratio (SNR) [10,11]. LIT is a powerful technique that utilizes IR photons to generate a specific temperature pattern, but only cracks with tiny tips and a triangular shape at the surface can be detected [12]. In SAM, the image is generated due to acoustic impedance mismatch caused by micro-cracks, but only cracks 5 – 10 µm can be detected, neglecting larger cracks [13].
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Dark Matter, what is it?

Dark Matter, what is it?

predicted, or they don’t exist at all. However, the idea that Dark Matter is made up of some sort of particle is still the most popular among scientists, so there are plans to make an even bigger detector, containing 7 tonnes of xenon. Experience so far suggests that patience will be an important component in this search. How long will it take to produce a credible negative result? Since the idea that Dark Matter is made up of particles is largely in agreement with our current understanding of particle physics, this is the most widely accepted idea. If these detectors don’t find any WIMPS or other Dark Matter particles, how long will it take to establish a solid negative result? If no WIMPS turn up, our ideas about the nature of space and the dynamics of the universe could be in for another upset. Is there something wrong with our understanding of gravity? Stay tuned!
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Indirect Search for Dark Matter

Indirect Search for Dark Matter

Dark Matter: indirect detection 1 its on the density of these objects in the galactic halo were discussed in [5]. Proposed extensions of the Standard Model or Su- persymmetric (SUSY) theories lead naturally to a series of candidates, which may be point-like or not. In the former case examples are sneutrinos, axinos, gravitinos, photinos, neutralinos, while in the latter, Q-balls are one interesting possibility [7,8], since their self-interaction cross section may be of the order of 20 mb or larger. These values are required for self-interacting dark mat- ter halo models, in order to remove the central density cusp predicted by simulations, but not seen in the rota- tion curve of luminous galaxies [9]. Superheavy particles
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