Low-mass WIMPs Research Articles

First results on low-mass WIMPs from the CDEX-1 experiment at the China Jinping underground laboratory

The China Dark matter Experiment collaboration reports the first experimental limit on WIMP dark matter from 14.6 kg-day of data taken with a 994 g p-type point-contact germanium detector at the China Jinping underground Laboratory where the rock overburden is more than 2400 m. The energy threshold achieved was 400 eVee. According to the 14.6 kg-day live data, we placed the limit of N= 1.75 * 10^{-40} cm^{2} at 90% confidence level on the spin-independent cross-section at WIMP mass of 7 GeV before differentiating bulk signals from the surface backgrounds.

DARK MATTER SEARCH WITH SUB-keV GERMANIUM DETECTORS AT THE CHINA JINPING UNDERGROUND LABORATORY

Germanium detectors with sub-keV sensitivities open a window to search for low-mass WIMP dark matter. The CDEX-TEXONO Collaboration is conducting the first research program at the new China Jinping Underground Laboratory with this approach. The status and plans of the laboratory and the experiment are discussed.

Connection of gamma rays, dark matter, and Higgs boson searches at the LHC

Motivated by the upcoming Higgs analyzes we investigate the importance of the complementarity of the Higgs boson chase on the low mass WIMP search in direct detection experiments and the gamma-ray emission from the Galactic Center measured by the Fermi-LAT telescope in the context of the $SU(3)_c\otimes SU(3)_L\otimes U(1)_N$. We obtain the relic abundance, thermal cross section, the WIMP-nucleon cross section in the low mass regime and network them with the branching ratios of the Higgs boson in the model. We conclude that the Higgs boson search has a profound connection to the dark matter problem in our model, in particular for the case that ($M_{WIMP} < 60$ GeV) the BR($H \rightarrow 2$ WIMPs) $\gtrsim 90%$. This scenario could explain this plateau of any mild excess regarding the Higgs search as well as explain the gamma-ray emission from the galactic center through the $b\bar{b}$ channel with a WIMP in the mass range of 25-45 GeV, while still being consistent with the current limits from XENON100 and CDMSII. However, if the recent modest excesses measured at LHC and TEVATRON are confirmed and consistent with a standard model Higgs boson this would imply that $ M_{WIMP} > 60 $ GeV, consequently ruling out any attempt to explain the Fermi-LAT observations.

Search for low-mass WIMPs with EDELWEISS-II heat-and-ionization detectors

We report on a search for low-energy (E < 20 keV) WIMP-induced nuclear recoils using data collected in 2009 - 2010 by EDELWEISS from four germanium detectors equipped with thermal sensors and an electrode design (ID) which allows to efficiently reject several sources of background. The data indicate no evidence for an exponential distribution of low-energy nuclear recoils that could be attributed to WIMP elastic scattering after an exposure of 113 kg.d. For WIMPs of mass 10 GeV, the observation of one event in the WIMP search region results in a 90% CL limit of 1.0x10^-5 pb on the spin-independent WIMP-nucleon scattering cross-section, which constrains the parameter space associated with the findings reported by the CoGeNT, DAMA and CRESST experiments.

Dark Matter Search with sub-keV Germanium Detectors at the China Jinping Underground Laboratory

Germanium detectors with sub-keV sensitivities open a window to search for low-mass WIMP dark matter. The CDEX-TEXONO Collaboration is conducting the first research program at the new China Jinping Underground Laboratory with this approach. The status and plans of the laboratory and the experiment are discussed.

Neutrinos from WIMP annihilation in the Sun: Implications of a self-consistent model of the Milky Way’s dark matter halo

Upper limits on the spin-independent (SI) as well as spin-dependent (SD) elastic scattering cross sections of WIMPs with protons, imposed by the Super-Kamiokande (S-K) upper limit on the neutrino flux from WIMP annihilation in the Sun, and their compatibility with the "DAMA-compatible" regions of the WIMP parameter space within which the annual modulation signal observed by the DAMA/LIBRA experiment is compatible with the null results of other direct detection experiments, are studied within the frame work of a self-consistent model of the finite-size dark matter (DM) halo of the Galaxy, the parameters of which are determined by a fit to the rotation curve data of the Galaxy. We find that the S-K implied upper limits on the WIMP-proton elastic cross section as a function of WIMP mass impose stringent restrictions on the branching fractions of the various WIMP annihilation channels. For SI interaction, while the S-K upper limits are consistent with the DAMA-compatible region of the WIMP parameter space if the WIMPs annihilate dominantly to $\bbarb$\ and/or $\cbarc$, portions of the DAMA-compatible region can be excluded if WIMP annihilations to $\tautau$ and $\nu\anu$ occur at larger than ~ 10% and 0.1% levels, respectively. For SD interaction, the restrictions on the possible annihilation channels are much more stringent, essentially ruling out the DAMA-compatible region of the WIMP parameter space if the relatively low-mass ($\sim$ 2 -- 20 GeV) WIMPs under consideration annihilate predominantly to any mixture of $\bbarb$, \ $\cbarc$, \ $\tautau$, \ and $\nu\anu$ final states.

Low-Mass WIMP Sensitivity and Statistical Discrimination of Electron and Nuclear Recoils by Varying Luke-Neganov Phonon Gain in Semiconductor Detectors

Amplifying the phonon signal in a semiconductor dark matter detector can be accomplished by operating at high voltage bias and converting the electrostatic potential energy into Luke-Neganov phonons. This amplification method has been validated at up to |E|=40V/cm without producing leakage in CDMSII Ge detectors, allowing sensitivity to a benchmark WIMP with mass = 8GeV and cross section 1.8e-42cm^2 assuming flat electronic recoil backgrounds near threshold. Furthermore, for the first time we show that differences in Luke-Neganov gain for nuclear and electronic recoils can be used to discriminate statistically between low-energy background and a hypothetical WIMP signal by operating at two distinct voltage biases. Specifically, 99% of events have p-value<1e-8 for a simulated 20kg-day experiment with a benchmark WIMP signal with mass =8GeV and cross section =3.3e-41cm^2.

The Directional Dark Matter Detector (D3)

Gas-filled Time Projection Chambers (TPCs) with Gas Electron Multipliers (GEMs) and pixels appear suitable for direction-sensitive WIMP dark matter searches. We present the background and motivation for our work on this technology, past and ongoing prototype work, and a development path towards an affordable, 1-$\rm m^3$-scale directional dark matter detector, \dcube. Such a detector may be particularly suitable for low-mass WIMP searches, and perhaps sufficiently sensitive to clearly determine whether the signals seen by DAMA, CoGeNT, and CRESST-II are due to low-mass WIMPs or background.

Simulation of the Directional Dark Matter Detector (D3) and Directional Neutron Observer (DiNO)

Preliminary simulation and optimization studies of the Directional Dark Matter Detector and the Directional Neutron Observer are presented. These studies show that the neutron interaction with the gas-target in these detectors is treated correctly by GEANT4 and that by lowering the pressure, the sensitivity to low-mass WIMP candidates is increased. The use of negative ion drift might allow us to search the WIMP mass region suggested by the results of the non-directional experiments DAMA/LIBRA, CoGeNT and CRESST-II.

THE SEARCH FOR DARK MATTER (WIMPs): AT LOW MASS AND WITH NEW METHODS

We briefly review the constraints on the search for low mass WIMPs (&lt;15 GeV) and the various experimental methods. These experiments depend on the response of detectors to low energy signals (less than 15 keV equivalent energy). We then describe recent fits to the data and attempt to determine L eff , the energy response at low energy. We find that the use of a liquid Xenon two-phase detector that employs the S2 data near threshold is the most sensitive current study of the low mass region. We rely on some talks at Dark Matter 2010.

Neutrino-nucleus coherent scattering and dark matter searches with sub-keV germanium detector

The theme of the TEXONO research program is on the studies of low energy neutrino and dark matter physics. The current goals are on the development of germanium detectors with sub-keV sensitivities to realize experiments on neutrino magnetic moments, neutrino-nucleus coherent scattering, as well as WIMP dark matter searches. A threshold of 100–200 eV was achieved with prototype detectors at the Kuo-Sheng Neutrino Laboratory. New limits were placed for low-mass WIMPs. The dark matter program will move to a new underground laboratory currently under construction in Sichuan, China.

DARK MATTER SEARCHES WITH SUB-keV GERMANIUM DETECTOR

The theme of the TEXONO research program is on the studies of low energy neutrino and dark matter physics. The current goals are on the development of germanium detectors with sub-keV sensitivities to realize experiments on neutrino magnetic moments, neutrino-nucleus coherent scattering, as well as WIMP dark matter searches. A threshold of 100–200 eV was achieved with prototype detectors at the Kuo-Sheng Neutrino Laboratory. New limits were placed for low-mass WIMPs. The dark matter program will move to a new underground laboratory currently under construction in Sichuan, China.

New limits on low-mass WIMP dark matter with sub-keV germanium detector

The current goals of the TEXONO research program are on the development of germanium detectors with sub-keV sensitivities to realize experiments on neutrino magnetic moments, neutrino-nucleus coherent scattering, as well as WIMP dark matter searches. A threshold of 220 eV was achieved with prototype detectors at the Kuo-Sheng Neutrino Laboratory. New limits were placed for the couplings of low-mass WIMPs with matter. Data are being taken with a 500 g Point Contact Germanium detector, where a threshold of ~350 eV was demonstrated. The dark matter program will evolve into a dedicated experiment at an underground laboratory under construction in Sichuan, China.

Spin-independent elastic WIMP scattering and the DAMA annual modulation signal

We discuss the interpretation of the annual modulation signal seen in the DAMA experiment in terms of spin-independent elastic WIMP scattering. Taking into account channeling in the crystal as well as the spectral signature of the modulation signal we find that the low-mass WIMP region consistent with DAMA data is confined to WIMP masses close to mχ ≃ 12 GeV, in disagreement with the constraints from CDMS and XENON. We conclude that even if channeling is taken into account this interpretation of the DAMA modulation signal is disfavoured. There are no overlap regions in the parameter space at 90% CL and a consistency test gives the probability of 1.2 × 10−5. We study the robustness of this result with respect to variations of the WIMP velocity distribution in our galaxy, by changing various parameters of the distribution function, and by using the results of a realistic N-body dark matter simulation. We find that only by making rather extreme assumptions regarding halo properties can we obtain agreement between DAMA and CDMS/XENON.

Prospects of cold dark matter searches with an ultra-low-energy germanium detector

The report describes the research program on the development of ultra-low-energy germanium detectors, with emphasis on WIMP dark matter searches. A threshold of 100 eV is achieved with a 20 g detector array, providing a unique probe to the low-mass WIMP. Present data at a surface laboratory is expected to give rise to comparable sensitivities with the existing limits at the 5 – 10 GeV WIMP-mass range. The projected parameter space to be probed with a full-scale, kilogram mass-range experiment is presented. Such a detector would also allow the studies of neutrino-nucleus coherent scattering and neutrino magnetic moments.

Cryogenic Dark Matter Search: limits and projections

The results from the second run of the Cryogenic Dark Matter Search experiment in the Soudan Underground Laboratory yields new exclusion limits on the coherent WIMPnucleon scalar cross-sections for WIMP masses above 15 GeV/c2. Two towers, each consisting of six detectors, were operated in the mine for 74.5 live days, doubling the previous Ge exposure to 34 kg-d after cuts for recoil energies of 10-100 keV. When combined with the data from the first run at Soudan, the new upper limit is 1.6 × 10−43 cm2 for a 60 GeV WIMP using the standard dark-matter halo and nuclear physics WIMP model. This is a factor of 2.5 lower than our previous limit and a factor of 10 lower than any other experiment. Limits from the Si data (12 kg-d) are less stringent, but extend the excluded region for low mass WIMPs. CDMS also has sensitivity to spin-dependent limits.

Further results from the CDMS experiment

The Cryogenic Dark Matter Search experiment utilizes discriminating detectors where both the recoil energy and ionization produced by each particle event are simultaneously measured. Here we present our latest results from operating 4 Ge (4×250g) and 2 Si (2×100g) detectors at the shallow Stanford site. Our new WIMP exclusion limit excludes new parameter space for low-mass WIMPS.

Limits on WIMP dark matter using sapphire cryogenic detectors

Data taken by CRESST with a cryogenic detector system based on 262 g sapphire crystals has been used to place limits on WIMP dark matter. The experiment was especially sensitive for low-mass WIMPs with spin-dependent cross sections and improves on existing limits in this region.

The search for dark matter.

We discuss the search for dark matter. We first review the data from LUX that excludes the low-mass WIMP region and slightly lowers the XENON100 limits. We provide a brief review of the problems with the claimed low-mass signals. We discuss the current expectations for SUSY-WIMP dark matter and show why very massive detectors like Darwin may be required. We discuss some theoretical predictions from the meeting. There was compelling evidence from events observed in the Galactic Center by Fermi-LAT of WIMP dark matter at the UCLA meeting. We recount the Richard Arnowitt Lectures at UCLA dark matter symposiums and his role in the development of the strategy to detect SUGRA dark matter.

Dark matter search with CRESST cryogenic detectors

Results of the CRESST experiment at Gran Sasso using 262-g sapphire calorimeters with tungsten phase transition thermometers are presented. Calibration and analysis methods are described. Data taken in 2000 have been used to place limits on WIMP dark matter particles in the Galactic halo. The sapphire detectors are especially sensitive to low-mass WIMPs with spin-dependent interaction and improve on existing limits in this region.