Search For Dark Matter Particles Research Articles

Invisible Higgs and dark matter

We investigate the possibility that a massive weakly interacting fermion simultaneously provides for a dominant component of the dark matter relic density and an invisible decay width of the Higgs boson at the LHC. As a concrete model realizing such dynamics we consider the minimal walking technicolor, although our results apply more generally. Taking into account the constraints from the electroweak precision measurements and current direct searches for dark matter particles, we find that such scenario is heavily constrained, and large portions of the parameter space are excluded.

Reducing potassium contamination for AMS detection of 39Ar with an electron-cyclotron-resonance ion source

The first application of 39Ar Accelerator Mass Spectrometry (AMS) at the ATLAS facility of Argonne National Laboratory was to date ocean water samples relevant to oceanographic studies using the gas-filled magnet technique to separate the 39K–39Ar isobars. In particular the use of a quartz liner in the plasma chamber of the electron cyclotron resonance ion source enabled a 39K reduction of a factor ∼130 compared to previous runs without liners, and allowed us to reach a detection sensitivity of 39Ar/Ar=4×10−17. In order to improve this sensitivity and allow the measurement of lower ratios, higher ion source currents and a lower overall 39K background are necessary. This paper summarizes our efforts to investigate new methods combining low level potassium cleaning techniques with the use of ultra-pure aluminum liners in the plasma chamber of the ion source. The aim of the study was to improve by 1–2 orders of magnitude the 39Ar detection sensitivity required in the selection of ultra-pure materials for detectors used in weakly interacting massive particle dark matter searches.

Direct search for low mass dark matter particles with CCDs

A direct dark matter search is performed using fully-depleted high-resistivity CCD detectors. Due to their low electronic readout noise (R.M.S. ∼7 eV) these devices operate with a very low detection threshold of 40 eV, making the search for dark matter particles with low masses (∼5 GeV) possible. The results of an engineering run performed in a shallow underground site are presented, demonstrating the potential of this technology in the low mass region.

Search for a light neutralino of cosmological interest at the CERN LHC

We address the problem of a search at the LHC for a neutralino whose mass is around 10 GeV, i.e. in the range of interest for present data of direct search for dark matter particles in the galactic halo. This light neutralino is here implemented in an effective Minimal Supersymmetric extension of the Standard Model at the electroweak scale without requirement of a gaugino mass unification at a grand unification scale. In this model, light neutralinos that have the right cosmological properties and are able to explain current results of direct dark matter detection naturally arise. Within this model we identify a specific benchmark which maximizes chances of detection at the LHC, and we determine its prospects of reconstructing the main features of the light neutralino framework at different stages of the LHC runs. Our main result is that the LHC will hardly properly reconstruct the mass of such a light neutralino, due to the intrinsic difficulty in reconstructing the mass of light stable particles in relativistic events. However, the associated measurement of the mass of the heavier neutralinos allows us to point toward the right pattern of gaugino nonuniversality. Other relevant parameters of this model, like slepton and squark masses, can be reconstructed to a good level of precision.

Closing in on supersymmetric electroweak baryogenesis with dark matter searches and the Large Hadron Collider

We study the impact of recent direct and indirect searches for particle dark matter on supersymmetric models with resonant neutralino- or chargino-driven electroweak baryogenesis (EWB) and heavy sfermions. We outline regions of successful EWB on the planes defined by gaugino and higgsino mass parameters, and calculate the portions of those planes excluded by dark matter search results, and the regions soon to be probed by current and future experiments. We conclude that dark matter searches robustly exclude a wino-like lightest supersymmetric particle in successful EWB regions. Bino-like dark matter is still a possibility, although one that will be probed with a modest improvement in the sensitivity of current direct and indirect detection experiments. We also calculate the total production cross section of chargino and neutralino pairs at the Large Hadron Collider, with a center of mass energy of 7 and 14 TeV.

Discussing direct search of dark matter particles in the minimal supersymmetric extension of the standard model with light neutralinos

We examine the status of light neutralinos in an effective Minimal Supersymmetric extension of the Standard Model (MSSM) at the electroweak scale which was considered in the past and discussed in terms of the available data of direct searches for dark matter (DM) particles. Our reanalysis is prompted by new measurements at the Tevatron and B-factories which might potentially provide significant constraints on the MSSM model. Here we examine in detail all these new data and show that the present published results from the Tevatron and B-factories have only a mild effect on the original light neutralino population. This population, which fits quite well the DAMA/LIBRA annual modulation data, would also agree with the preliminary results of CDMS, CoGeNT and CRESST, should these data, which are at present only hints or excesses of events over the expected backgrounds, be interpreted as authentic signals of DM. For the neutralino mass we find a lower bound of 7-8 GeV. Our results differ from some recent conclusions by other authors because of a few crucial points which we try to single out and elucidate.

The indirect search for dark matter with IceCube

We revisit the prospects for IceCube and similar kilometer-scale telescopes to detect neutrinos produced by the annihilation of weakly interacting massive dark matter particles (WIMPs) in the Sun. We emphasize that the astrophysics of the problem is understood; models can be observed or, alternatively, ruled out. In searching for a WIMP with spin-independent interactions with ordinary matter, IceCube is only competitive with direct detection experiments if the WIMP mass is sufficiently large. For spin-dependent interactions IceCube already has improved the best limits on spin-dependent WIMP cross sections by two orders of magnitude. This is largely due to the fact that models with significant spin-dependent couplings to protons are the least constrained and, at the same time, the most promising because of the efficient capture of WIMPs in the Sun. We identify models where dark matter particles are beyond the reach of any planned direct detection experiments while being within reach of neutrino telescopes. In summary, we find that, even when contemplating recent direct detection results, neutrino telescopes have the opportunity to play an important as well as complementary role in the search for particle dark matter.

Interpreting the recent results on direct searches for dark matter particles in terms of relic neutralinos

The most recent results from direct searches for dark matter particles in the Galactic halo are examined in terms of an effective minimal supersymmetric extension of the standard model at the electroweak scale without unification of gaugino masses. We show that the annual-modulation effect at $8.2\ensuremath{\sigma}$ C.L. recently presented by the DAMA Collaboration, as the result of a combined analysis of the DAMA/NaI and the DAMA/LIBRA experiments for a total exposure of 0.82 ton yr, fits remarkably well with what is expected for relic neutralinos for a wide variety of weakly interacting massive particle distribution functions. Bounds derivable from other measurements of direct searches for dark matter particles are analyzed. We stress the role played by the uncertainties affecting the neutralino-quark couplings arising from the involved hadronic quantities. We also examine how present data on cosmic antiprotons can help in constraining the neutralino configurations selected by the DAMA effect, in connection with the values of the astrophysical parameters. Perspectives for measurements of antideuterons, possibly produced in the Galactic halo by self-annihilation of neutralinos belonging to the DAMA configurations, are examined. Finally, we discuss how findings at the LHC would impact on these issues.

Poiski chastits temnoi materii

Poiski chastits temnoi materii

THE SEARCH FOR DARK MATTER FROM SPACE AND ON THE EARTH

We first show that the MOND concept is very unlikely: nonbaryonic dark matter exists. We then discuss dwarf special galaxies that in some cases appear to be nearly pure dark matter systems. The search for dark matter particles can be carried out from space (sterile neutrinos neutralino annihilation) or on the Earth (direct detection). We describe progress in these areas and focus on the progress of the ZEPLIN II detector now taking data.1,2.

Cosmic-ray electron spectrum above 100 GeV from PPB-BETS experiment in Antarctica

Cosmic-ray electrons have been observed in the energy region from 10 GeV to 1 TeV with the PPB-BETS by a long duration balloon flight using a Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an average altitude of 35 km in January 2004. The PPB-BETS detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. In the study of cosmic-ray electrons, there have been some suggestions that high-energy electrons above 100 GeV are a powerful probe to identify nearby cosmic-ray sources and search for particle dark matter. In this paper, we present the energy spectrum of cosmic-ray electrons in the energy range from 100 GeV to 1 TeV at the top of atmosphere, and compare our spectrum with the results from other experiments.

Dark matter signals: from underground to space investigations

The DAMA/NaI experiment (≃ 100 kg highly radiopure NaI(Tl)) at the Gran Sasso National Laboratory of the I.N.F.N. had the unique feature to effectively investigate the presence of Dark Matter particle in the galactic halo by exploiting the model independent annual modulation signature. With a total exposure of more than 10 5 kg × day, collected over seven annual cycles, it has pointed out at 6.3 σ C.L. an effect which satisfies all the many peculiarities of the signature. Neither systematics nor side reactions able to account for the observed effect were found. No experiment whose result can be directly compared in a model independent way with the experimental one of DAMA/NaI is available so far. Several (but still few with respect to the possibilities) corollary model dependent quests for the candidate particle have also been carried out. At present the second generation DAMA/LIBRA set-up (≃ 250 kg highly radiopure NaI(Tl)) is in operation. Positive model dependent hints have also been pointed out by indirect searches for Dark Matter particles in space experiments and are not in contradiction with DAMA/NaI. Thus, the ongoing of model independent experiment deep underground and the new space experiments foreseen in incoming years will certainly further increase our knowledge of the field.

Prospects for detecting dark matter with neutrino telescopes in light of recent results from direct detection experiments

Direct detection dark matter experiments, lead by the CDMS collaboration, have placed increasingly stronger constraints on the cross sections for elastic scattering of WIMPs on nucleons. These results impact the prospects for the indirect detection of dark matter using neutrino telescopes. With this in mind, we revisit the prospects for detecting neutrinos produced by the annihilation of WIMPs in the Sun. We find that the latest bounds do not seriously limit the models most accessible to next generation kilometer-scale neutrino telescopes such as IceCube. This is largely due to the fact that models with significant spin-dependent couplings to protons are the least constrained and, at the same time, the most promising because of the efficient capture of WIMPs in the Sun. We identify models where dark matter particles are beyond the reach of any planned direct detection experiments while within reach of neutrino telescopes. In summary, we find that, even when contemplating recent direct detection results, neutrino telescopes still have the opportunity to play an important as well as complementary role in the search for particle dark matter.

The XENON dark matter search: status of XENON10

The XENON experiment searches for dark matter particles called WIMPs using liquid xenon (LXe) as the active target. The detector is a 3D position sensitive Time Projection Chamber optimized to simultaneously measure the ionization and scintillation produced by a recoil event of energy as low as 16 keV. The distinct ratio of the two signals for nuclear recoils arising from WIMPs and neutrons and for electron recoils from the dominant gamma-ray background determines its event-by-event discrimination. With 1 ton of LXe distributed in ten identical modules, the proposed XENON1T experiment will achieve a sensitivity more than a factor of thousand beyond current limits. A phased program will test a 10 kg detector (XENON10) followed by a 100 kg (XENON100) one as unit module for the XENON1T scale experiment. We review the progress of the XENON R & D phase before presenting the status of XENON10. The experiment will be based at the Gran Sasso Underground Laboratory and is expected to start data taking in early 2006.

High Energy Neutrinos in Super-Kamiokande

The new analysis of Super-Kamiokande atmospheric neutrino data, based on a subsample of higher precision data is reported. The plot of the muon neutrino survival probability as a function of the ratio of the distance over neutrino energy displays a dip just where the first oscillation maximum is expected from the standard analysis. As a result the parameters of the transitions νμ↔ντ are better constrained: 1.9×10−3<Δm2<3.0×10−3 eV2 and sin22θ>0.90 at 90% C.L. A signal of WIMP annihilations in the Sun, the core of the Earth or the Galactic Center has been searched in a sample of upward through-going muons, produced by neutrino interactions outside of detector. No statistically significant signal has been observed. Upper limits of the muon fluxes are compared with results from other neutrino detectors. Also upper limits on cross section for the WIMP nucleon interaction are derived and compared with corresponding results from direct searches of dark matter particles.

DARK MATTER IN THE UNIVERSE

Evidences for the existence of dark matter in the Universe are briefly reviewed and, in particular, the nature of the galactic halo. Possible candidates, point-like or not, issued from extensions of the Standard Model or Supersymmetric theories are examined. Finally, direct and indirect searches for dark matter particles are summarized.

Dark Matter search

Some general arguments on the particle Dark Matter search are addressed. The WIMP direct detection technique is mainly considered and recent results obtained by exploiting the annual modulation signature are summarized.

Supersymmetric dark matter: direct detection

Direct search for dark matter particles is a good tool for probing supersymmetry, especially for models where the neutralino is the relic candidate. The extent of exploration achieved by current experimental sensitivities is discussed for various supersymmetric schemes, which differ among themselves in some underlying theoretical assumptions (SUGRA, nuSUGRA and effMSSM). The interesting result is that direct searches are actually probing supersymmetric configurations with neutralinos of cosmological relevance.

First Dark Matter Limits from a Large-Mass, Low-Background, Superheated Droplet Detector

We report on the fabrication aspects and calibration of the first large active mass ( approximately 15 g) modules of SIMPLE, a search for particle dark matter using superheated droplet detectors (SDDs). While still limited by the statistical uncertainty of the small data sample on hand, the first weeks of operation in the new underground laboratory of Rustrel-Pays d'Apt already provide a sensitivity to axially coupled weakly interacting massive particles (WIMPs) competitive with leading experiments, confirming SDDs as a convenient, low-cost alternative for WIMP detection.

Charge and heat collection in a 70 g heat/ionization cryogenic detector for dark matter search

We present detailed studies of the physical mechanisms underlying the collection of the charge carriers and of the thermal energy in a heat/ionization germanium particle detector operated at 20–28 mK, together with a presentation of its main performances. This detector is devoted to the search of dark matter particles, taking advantage of the double signal to reject background induced events. In what concerns the ionization channel, the current–voltage characteristics, energy resolution, time stability, and pulse height bias dependence are presented. A mechanism is proposed to explain the fact that the p-i-n diode maintains some rectifying properties in spite of the very low temperature. The energy resolution is 1 keV full width at half maximum (FWHM) at 86.5 keV, and the stability time is several days. A calculation of the carrier trapping contribution to the energy resolution and bias dependence is performed and its results compared to the data. The bias dependence is interpreted within a “hot” carrier model in which the shape of the trapping cross section as a function of the electric field is investigated. The time stability behavior is interpreted in terms of a space charge evolution due to traps ionization. The reasons why the densities of ionized levels are minimized are discussed. It is shown that one of them is related to the low currents obtained at rather large biases because of the choice of a p-i-n scheme. In what concerns the heat channel, an analysis of the heat flow in the thermal circuit is performed to explain the shape and amplitude of the heat pulses. The risetimes are well accounted for, allowing a determination of the NTD electronic specific heat, (1.80±0.45)×10−6 T J K−1 cm−3. The analysis of the two decay times leads to an interpretation in terms of partial thermalization of the ballistic phonons in the metallic parts of the detector. This mechanism allows to estimate the experimental responsivities and energy resolutions [6 and 20 nV/keV; 1.25 and 2.8 keV (FWHM) for sensor temperatures of respectively 20.5 and 28 mK]. Both the ionization and heat channel results are used to draw guidelines for detector performance improvements and mass increase.