Narrow Results

It is now well established and accepted that roughly 25% of the total mass-energy density of the Universe is in the form of non-relativistic particles. That these particles, referred to as Dark Matter, have remained a mystery has served as motivation for the design and implementation of increasingly ingenious and far reaching experiments in an attempt to identify and understand them. This paper will review various ongoing Dark Matter searches with focus on the variety of techniques and implementation used to both detect the rare Dark Matter interactions as well as reject the vast number of background events.

Direct detection of WIMPs is key to understand the origin and composition of Dark Matter. Among the many experimental techniques available, those providing directional information have the potential of yielding an unambiguous observation of WIMPs even in the presence of insidious backgrounds. A measurement of the distribution of arrival direction of WIMPs can also discriminate between Galactic Dark Matter halo models. Here, we will discuss the motivation for directional detectors and review the experimental techniques used by the various experiments. We will then describe the DMTPC detector in more detail.

In this article I review model-independent procedures for extracting properties of Weakly Interacting Massive Particles (WIMPs) from direct Dark Matter detection experiments. Neither prior knowledge about the velocity distribution function of halo Dark Matter particles nor about their mass or cross sections on target nucleus is needed. The unique required information is measured recoil energies from experiments with different detector materials.

It was recently proposed that weakly interacting massive particles (WIMP) may provide new ways of generating the observed baryon asymmetry in the early universe, as well as addressing the cosmic coincidence between dark matter (DM) and baryon abundances. This suggests a new possible connection between weak scale new particle physics and modern cosmology. This review summarizes the general ideas and simple model examples of the two recently proposed WIMP baryogenesis mechanisms: baryogenesis from WIMP DM annihilation during thermal freeze-out, and baryogenesis from metastable WIMP decay after thermal freeze-out. This review also discusses the interesting phenomenology of these models, in particular, the experimental signals that can be probed in the intensity frontier experiments and the large hadron collider (LHC) experiments.

We consider the hypothesis that dark matter is made of weakly interacting massive particles (WIMPs) and describe how their pair annihilation in the galactic halo generates exotic cosmic ray fluxes. Features for generic WIMP models are reviewed, pointing out cases in which clear signatures arise. Implications from available and upcoming measurements are discussed.

The effect pointed out by A. B. Migdal in 1940's (hereafter named Migdal effect) has so far been usually neglected in the direct searches for WIMP Dark Matter candidates. This effect consists in the ionization and the excitation of bound atomic electrons induced by the recoiling atomic nucleus. In the present paper the related theoretical arguments are developed and some consequences of the proper accounting for this effect are discussed by some examples of practical interest.

Theoretical and experimental techniques employed in dedicated searches for dark matter at hadron colliders are reviewed. Bounds from the 7 TeV and 8 TeV proton–proton collisions at the Large Hadron Collider (LHC) on dark matter interactions have been collected and the results interpreted. We review the current status of the Effective Field Theory picture of dark matter interactions with the Standard Model. Currently, LHC experiments have stronger bounds on operators leading to spin-dependent scattering than direct detection experiments, while direct detection probes are more constraining for spin-independent scattering for WIMP masses above a few GeV.

We study the spin-dependent WIMP scattering off nuclei for a variety of targets of experimental interest. In evaluating the spin structure functions, we have included the recently proposed leading long-range two-body currents in the most important isovector contribution. We show, however, that such effects are essentially independent of the target nucleus and, as a result, they can be treated as a mere renormalization of the effective nucleon cross-section or, equivalently, of the corresponding effective coupling, with reduction factors around 25%. Using these effects in the spin structure functions, we compute the relevant event rates due to the spin for various targets of experimental interest.

In this paper, we revisit our model-independent methods developed for reconstructing properties of Weakly Interacting Massive Particles (WIMPs) by using measured recoil energies from direct Dark Matter detection experiments directly and take into account more realistically non-negligible threshold energy. All expressions for reconstructing the mass and the (ratios between the) spin-independent and the spin-dependent WIMP–nucleon couplings have been modified. We focus on low-mass ($m_{\chi }\lesssim 15$ GeV) WIMPs and present the numerical results obtained by Monte Carlo simulations. Constraints caused by non-negligible threshold energy and technical treatments for improving reconstruction results will also be discussed.

We reexamine the model-independent data analysis methods for extracting properties of Weakly Interacting Massive Particles (WIMPs) by using data (measured recoil energies) from direct Dark Matter detection experiments directly and, as a more realistic study, consider a small fraction of residue background events, which pass all discrimination criteria and then mix with other real WIMP-induced signals in the analyzed data sets. In this talk, the effects of residue backgrounds on the determination of the WIMP mass as well as the spin-independent WIMP coupling on nucleons will be discussed.

We shall consider the problem of Dark Matter (DM) in torsion gravity with Dirac matter fields; we will consider the fact that if Weakly-Interacting Massive Particles in a bath are allowed to form condensates then torsional effects may be relevant even at galactic scales: we show that torsionally-gravitating Dirac fields have interesting properties for the problem of DM. We discuss consequences.

In this paper, we investigate the modification of our expressions developed for the model-independent data analysis procedure of the reconstruction of the (time-averaged) one-dimensional velocity distribution of galactic weakly interacting massive particles (WIMPs) with a nonnegligible experimental threshold energy. Our numerical simulations show that, for a minimal reconstructable velocity of as high as km/s, our model-independent modification of the estimator for the normalization constant could provide precise reconstructed velocity distribution points to match the true WIMP velocity distribution with ≲ 10% bias.

It is known that the smallest size of the structures of the Universe with the weakly interacting massive dark matter is determined by the scale that enters the Hubble horizon at the time of kinetic decoupling of WIMP. This comes from the fact that the perturbation at smaller scales is erased due to the collisional damping during the kinetic decoupling. However the isocurvature mode is not affected and continue to be constant. We discuss about the generation of the isocurvature mode of WIMP dark matter at small scales recently found by Choi, Gong, and Shin¹ and its implications for the indirect detection of dark matter through the formation of the small size of halos.

The XENON experiment aims at the direct detection of dark matter in the form of Weakly Interacting Massive Particles (WIMPs) via their elastic scattering off Xe nuclei. The final detector will have a fiducial mass of 1000 kg, distributed in 10 independent liquid xenon time projection chambers (TPCs). Such an experiment will be able to probe the lowest interaction cross-section predicted by SUSY models. The TPCs are operated in dual (liquid/gas) phase, to allow a measurement of nuclear recoils down to < 10 keV energy, via simultaneous detection of the ionization, through secondary scintillation in the gas, and primary scintillation in the liquid. The distinct ratio of primary to secondary scintillation for nuclear recoils from WIMPs (or neutrons), and for electron recoils from background, is used for the event-by-event discrimination. As part of the R&D phase, we built a first XENON module (XENON10) with 15 kg fiducial mass and installed it underground, at the Laboratori Nazionali del Gran Sasso (LNGS), on March 2006. XENON10 has accumulated an exposure of more than 30 live days, operating with quite stable condition. A preliminary analysis of the background data is presented here.

Micropattern detectors (MPD) and in particular MICROMEGAS are being developed very actively in recent years. While increasingly used now in high energy physics experiments, their application to rare event searches is relatively more recent. In this talk the status of three initiatives in this respect are presented: MICROMEGAS for axion searches in the CAST experiment at CERN, the use of MICROMEGAS technology to measure the recoil direction in WIMP searches, and the development of the spherical TPC concept with applications in low energy neutrino detection.

IceCube is a kilometer scale high-energy neutrino observatory, currently under construction at the South Pole. It is a photo-detector, using the deep Antarctic ice as detection medium for the Cherenkov photons induced by relativistic charged particles. These charged particles may be atmospheric muons or reaction products from neutrino interactions in the vicinity of the instrumented volume. The experiment searches for neutrinos originating in astrophysical sources, and can also detect neutrinos from WIMP interaction in the Sun or Earth. In the last two austral summers, 9 in-ice strings and 16 surface IceTop stations (out of up to 80 planned) were successfully deployed, and the detector has been taking data ever since. In this proceedings, IceCube design, present status, performance and dark matter detection sensitivities will be discussed.

We review various issues related to the direct detection of constituents of dark matter, which are assumed to be Weakly Interacting Massive Particles (WIMPs). We specifically consider heavy WIMPs such as: 1) The lightest supersymmetric particle LSP or neutralino. 2) The lightest Kaluza-Klein particles in theories of extra dimensions and 3) other extensions of the standard model. In order to get the event rates one needs information about the structure of the nucleon as well as as the structure of the nucleus and the WIMP velocity distribution. These are also examined Since the expected event rates for detecting the recoiling nucleus are extremely low and the signal does not have a characteristic signature to discriminate against background we consider some additional aspects of the WIMP nucleus interaction, such as the periodic behavior of the rates due to the motion of Earth (modulation effect). Since, unfortunately, this is characterized by a small amplitude we consider other options such as directional experiments, which measure not only the energy of the recoiling nuclei but their direction as well. In these, albeit hard, experiments one can exploit two very characteristic signatures: a)large asymmetries and b) interesting modulation patterns. Furthermore we extended our study to include evaluation of the rates for other than recoil searches such as: i) Transitions to excited states, ii) Detection of recoiling electrons produced during the neutralino-nucleus interaction and iii) Observation of hard X-rays following the de-excitation of the ionized atom.

We consider the hypothesis that dark matter is made of weakly interacting massive particles (WIMPs) and describe how their pair annihilation in the galactic halo generates exotic cosmic ray fluxes. Features for generic WIMP models are reviewed, pointing out cases in which clear signatures arise. Implications from available and upcoming measurements are discussed.

IceCube is a high energy (E ≳ TeV) neutrino telescope currently under construction at the South Pole. The final instrumented volume will be approximately 1 km³ and the complementing surface array (IceTop) will be 1 km² in area. The main objective of IceCube is the search for extraterrestrial sources of high energy neutrinos. IceCube's prototype detector (AMANDA) produced data sets starting in 1997. These have been analyzed in the search for high-energy neutrinos from diffuse and point sources. AMANDA has also performed searches for Dark Matter accumulated in the center of the Earth and the Sun and for relativistic magnetic monopoles. This papers reports the implications of the AMANDA searches and reports on the status of IceCube construction.

We present the current status of the Cryogenic Dark Matter Search (CDMS). The five tower detector array, total 30 detectors, are running stable since October 2006. We have accumulated more than 900 kg-days of low background data. We also summarize the prospect of SuperCDMS project.