Analysis of the XENON100 dark matter search data

The XENON100 experiment, situated in the Laboratori Nazionali del Gran Sasso, aims at the direct detection of dark matter in the form of weakly interacting massive particles (WIMPs), based on their interactions with xenon nuclei in an ultra low background dual-phase time projection chamber. This paper describes the general methods developed for the analysis of the XENON100 data. These methods have been used in the 100.9 and 224.6 live days science runs from which results on spin-independent elastic, spin-dependent elastic and inelastic WIMP-nucleon cross-sections have already been reported.     

A CsI low-temperature detector for dark matter search

Cryogenic detectors have a long history of success in the field of rare event searches. In particular scintillating calorimeters are very suitable detectors for this task since two signals are induced by a particle interaction in a scintillating crystal. The thermal signal provides a precise measurement of the deposited energy while the simultaneously measured scintillation light signal yields particle discrimination as the amount of produced scintillation light depends on the nature of the interacting particle. We investigate the calorimetric properties and background rejection capabilities of two large CsI (undoped) crystals (∼122  g each) operated as scintillating calorimeters at milli-Kelvin temperatures. Furthermore, we discuss the feasibility of this detection approach towards a future background-free dark matter experiment based on alkali halide crystals, with active particle discrimination via the two-channel detection.     

Neutron background in large-scale xenon detectors for dark matter searches

Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10⁻⁹–10⁻¹⁰ pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector.     

Performance of a lithium fluoride bolometer for Tokyo dark matter search experiment

The performance of a 21-g lithium fluoride bolometer is presented. The background spectrum was measured in the surface laboratory. We derive an exclusion plot for the spin-dependent coupled Weakly Interacting Massive Particles (WIMPs) cross section.     

TeV dark matter in the disk

DAMA and CoGeNT annual modulation data and, CDMS-II, EDELWEISS-II, CRESST excesses of events over the expected background are reanalyzed in terms of a dark matter particle signal considering the case of a rotating halo. It is found that the configurations of very high mass dark matter particles in a corotating cold flux are favored by data. A similar high-mass/low-velocity solution could be of interest in the light of the positron/electron excess measured by PAMELA and Fermi LAT in cosmic rays.     

Microlensing in dark matter haloes

Using eight dark matter haloes extracted from fully self-consistent cosmological N -body simulations, we perform microlensing experiments. A hypothetical observer is placed at a distance of 8.5 kpc from the centre of the halo measuring optical depths, event durations and event rates towards the direction of the Large Magellanic Cloud. We simulate 1600 microlensing experiments for each halo. Assuming that the whole halo consists of massive astronomical compact halo objects (MACHOs),   f = 1.0  , and a single MACHO mass is   m _M= 1.0 M_⊙  , the simulations yield mean values of  τ= 4.7^+5.0_−2.2× 10⁻⁷  and  Γ= 1.6^+1.3_−0.6× 10⁻⁶  events star⁻¹ yr⁻¹. We find that triaxiality and substructure can have major effects on the measured values so that τ and Γ values of up to three times the mean can be found. If we fit our values of τ and Γ to the MACHO collaboration observations, we find   f = 0.23^+0.15_−0.13  and   m _M= 0.44^+0.24_−0.16  . Five out of the eight haloes under investigation produce f and m _M values mainly concentrated within these bounds.     

An excursion set model for the distribution of dark matter and dark matter haloes

A model of the gravitationally evolved dark matter distribution, in the Eulerian space, is developed. It is a simple extension of the excursion set model that is commonly used to estimate the mass function of collapsed dark matter haloes. In addition to describing the evolution of the Eulerian space distribution of the haloes, the model allows one to describe the evolution of the dark matter itself. It can also be used to describe density profiles, on scales larger than the virial radius of these haloes, and to quantify the way in which matter flows in and out of Eulerian cells. When the initial Lagrangian space distribution is white noise Gaussian, the model suggests that the Inverse Gaussian distribution should provide a reasonably good approximation to the evolved Eulerian density field, in agreement with numerical simulations. Application of this model to clustering from more general Gaussian initial conditions is discussed at the end.     

Missing dark matter in the local universe

A sample of 11 thousand galaxies with radial velocities V _LG < 3500 km/s is used to study the features of the local distribution of luminous (stellar) and dark matter within a sphere of radius of around 50 Mpc around us. The average density of matter in this volume, ?? _m,loc = 0.08 ± 0.02, turns out to be much lower than the global cosmic density ?? _m,glob = 0.28 ± 0.03. We discuss three possible explanations of this paradox: 1) galaxy groups and clusters are surrounded by extended dark halos, the major part of the mass of which is located outside their virial radii; 2) the considered local volume of the Universe is not representative, being situated inside a giant void; and 3) the bulk of matter in the Universe is not related to clusters and groups, but is rather distributed between them in the form of massive dark clumps. Some arguments in favor of the latter assumption are presented. Besides the two well-known inconsistencies of modern cosmological models with the observational data: the problem of missing satellites of normal galaxies and the problem of missing baryons, there arises another one??the issue of missing dark matter.     

Conformally coupled dark matter

Dark matter is obtained from a scalar field coupled conformally to gravitation, the scalar being a relict of Dirac's gauge function. This conformally coupled dark matter includes a gas of very light (m 2.25 × 10^–34 eV) neutral bosons having spin 0, as well as a time-dependent global scalar field, both pervading all of the cosmic space. The time-development of this dark matter in the expanding F-R-W universe is investigated, and an acceptable cosmological behaviour is obtained.     

Rydberg matter in space: low-density condensed dark matter

Here Rydberg matter is proposed as a candidate for the missing dark matter or dark baryonic matter in the Universe. Spectroscopic and other experimental studies give valuable information on the properties of Rydberg matter, especially its very weak interaction with light caused by the very small overlap with low states, and because of the necessary two-electron transitions even for disturbed matter. Recently, the unidentified infrared (UIR) bands have been shown to agree well with calculations and experiments on Rydberg matter. This is the reason for the present, somewhat speculative, proposal that dark matter has, at least partially, the form of Rydberg matter. The UIR bands have also been observed directly in emission from Rydberg matter in the laboratory. The unique space-filling properties of Rydberg matter are described: a hydrogen atom in this matter occupies a volume  5×10¹²  times larger than in its ground state or in a hydrogen molecule.     

Figure rotation of dark haloes in cold dark matter simulations

We investigate the figure rotation of dark matter haloes identified in Λ cold dark matter (CDM) simulations. We find that when strict criteria are used to select suitable haloes for study, five of the 222 haloes identified in our   z = 0  simulation output undergo coherent figure rotation over a  5 h ⁻¹ Gyr  period. We discuss the effects of varying the selection criteria and find that pattern speeds for a much larger fraction of the haloes can be measured when the criteria are relaxed. Pattern speeds measured over a  1 h ⁻¹ Gyr  period follow a lognormal distribution, centred at  Ω_p= 0.2 h rad Gyr⁻¹  with a maximum value of 0.94 h rad Gyr⁻¹. Over a  5 h ⁻¹ Gyr  period, the average pattern speed of a halo is about  0.1 h rad Gyr⁻¹  and the largest pattern speed found is  0.24 h rad Gyr⁻¹  . Less than half of the selected haloes showed alignment between their figure rotation axis and minor axis, the exact fraction being somewhat dependent on how one defines a halo. While the pattern speeds observed are lower than those generally thought capable of causing spiral structure, we note that coherent figure rotation is found over very long periods and argue that further simulations would be required before strong conclusions about spiral structure in all galaxies could be drawn. We find no correlation between halo properties such as total mass and the pattern speed.     

Performances and prospects of the “ROSEBUD” dark matter search experiment

A cryogenic search for WIMP Dark Matter with small sapphire bolometers through the WIMP scattering off Al₂O₃ nuclei, the ROSEBUD (Rare Objects SEarch with Bolometers UndergrounD) experiment, is being installed in the Canfranc Underground Laboratory (Spain) at 2450 m water equivalent. The performances of the bolometers, the radioactive background expected from the measurement of the radiopurity of the ROSEBUD components and the estimated sensitivity of the experiment for low mass WIMP detection are presented.     

Constraints on dark matter in the solar system

We have searched for and estimated the possible gravitational influence of dark matter in the Solar system based on the EPM2011 planetary ephemerides using about 677 thousand positional observations of planets and spacecraft. Most of the observations belong to present-day ranging measurements. Our estimates of the dark matter density and mass at various distances from the Sun are generally overridden by their errors (σ). This suggests that the density of dark matter ρ _dm, if present, is very low and is much less than the currently achieved error of these parameters. We have found that ρ _dm is less than 1.1 × 10^?20 g cm^?3 at the orbital distance of Saturn, ρ _dm < 1.4 × 10^?20 g cm^?3 at the orbital distance of Mars, and ρ _dm < 1.4 × 10^?19 g cm^?3 at the orbital distance of the Earth. We also have considered the case of a possible concentration of dark matter to the Solar system center. The dark matter mass in the sphere within Saturn’s orbit should be less than 1.7 × 10^?10 M _⊙ even if its possible concentration is taken into account.