Matter Searches Research Articles

Search for dark matter by GENIUS-TF and GENIUS

Search for dark matter by GENIUS-TF and GENIUS

Search for dark matter with the PICASSO experiment

Search for dark matter with the PICASSO experiment

The Galactic Halo from Microlensing

The status of the microlensing search for galactic dark matter in the form of massive astronomical compact halo objects (machos) is reviewed. Unresolved issues are discussed, as well as possible ways to solve these.

DARK MATTER SEARCHES

One of the most central problems in astronomy and cosmology is to understand the nature of the dark matter pervading the universe. And as we will see, the solution may involve particle physics. We review the current attempts to directly detect this dark matter. We have included in this written version the most recent results that were not available at the time of the Lepton Photon conference: the 5.7 year MACHO data [1], the 4 year modulation evidence for WIMPs claimed by DAMA [2], and the new WIMP results of CDMS [3]. Considerable evidence (see e.g., [4]) gathered in the last fifteen years indicates that at least 90% of the mass in the universe is dark: it does not emit nor absorb any form of electromagnetic radiation. Once a subject of controversy among astronomers, the existence of dark matter is now well established at a variety of scales. The debate has shifted to measuring the amount of dark matter in the universe, studying its distribution and unraveling its nature. Figure 1 presents a map of the possibilities. A central question is whether this dark matter is made of ordinary baryonic matter or is non-baryonic. Note that the problem has become even more complex, because the recent measurement of supernovae at high redshift [5, 6] may indicate an additional diffuse component, possibly with negative pressure, such as a cosmological constant. We will review in Section 2 the astrophysical hints for the nature of dark matter. We need both dark baryons and non-baryonic dark matter. Section 3 will summarize searches for baryons. We review in Section 4 the various searches for non-baryonic dark matter before focusing in Section 5 on the detection efforts for Weakly Interacting Massive Particles (WIMPs).

Neutrinoless double-beta decay and dark matter search with GENIUS

The potential of the GENIUS (GErmanium in liquid NItrogen Underground Setup) experiment, proposed as the successor of the Heidelberg-Moscow experiment, for the search for neutrinoless double-beta decay, the direct search for neutralino Cold Dark Matter, and for other physics beyond the Standard Model will be presented. The current status of the Heidelberg-Moscow experiment will be reviewed.

Experimental searches for hot and cold dark matter

A way to fix the overproduction by cold dark matter of small-scale structure in the universe is to add hot dark matter in the form of neutrinos. Unlike cold dark matter, such as supersymmetric neutralinos, which very likely could be detected directly, the nature of the neutrinos must be determined from terrestrial experiments. The LSND experiment may be providing such evidence, since in a v¯ u beam 22 events consistent with v¯ u p → e + n are seen, whereas only 4.6 ± 0.6 are expected from backgrounds; the probability of this being a fluctuation is −7 . If subsequent analysis shows a similar effect from the independent channel ν μ → ν e , then this would imply a neutrino mass difference which would contribute significantly to the dark matter of the universe. Explaining also the solar and atmospheric neutrino deficits results in a neutrino mass pattern which gives a cold + hot dark matter mix which fits the structure of the universe on all scales and requires a critical density universe and a universe age compatible with that of the oldest stars. Further evidence for this mass pattern comes from the production of heavy elements in supernovae. The net for cold dark matter must be cast more widely, but the new experiments just starting have a good chance of detecting neutralinos, if these are indeed the major constituent of the universe.

Pre-Main-Sequence Star Candidates in the Bar of the Large Magellanic Cloud

Candidate pre-main-sequence stars were observed in the bar of the Large Magellanic Cloud during the search for dark matter in the galactic halo. Seven blue stars of apparent visual magnitude 15 to 17 had irregular photometric variations and hydrogen emission lines in their optical spectra, which suggested that these stars are pre-main-sequence stars of about 10 solar masses. These stars are slightly more massive and definitely more luminous than are Herbig AeBe pre-main-sequence stars in our own galaxy. Continued observations of these very young stars from another galaxy, which are probably at the pre-hydrogen-burning stage, should provide important clues about early stages of star formation.

A Search for annual and daily modulations of dark matter with NaI scintillators at Canfranc

A search for cold dark matter has been carried out at the Canfranc Underground Laboratory with a set of three sodium iodide scintillators of 10.7 kg each, during two years of data taking. The results, corresponding to an exposure of 4613.6 kg day are presented in the form of exclusion plots σ(m) for spin-independent and spin-dependent WIMP-matter interacions, by conventionally comparing the observed rate with the expected signal. Distinctive features of the CDM signal, like annual and daily modulations have been looked for, in, respectively, 1342.85 kg day and 2769.6 kg day of data. The non observance of such modulations have been used to draw stringer exclusion plots than those derived from the previous, conventional method.

Search for supersymmetric dark matter with Baksan Underground telescope

The results of a search for high energy neutrino signals from hypothetical supersymmetric dark matter based on the data collected with the Baksan Underground Scintillator Telescope are presented. The upward going muon statistics collected during 15 years of operation is used. The limits on the neutrino flux from neutralino annihilations in the Sun and Earth are given for a wide range of model parameters. The region of these parameters, excluded by Baksan data at the 90% c.l. is obtained.

Gravitational microlensing experiments: A review

Search for Galactic dark matter in the form of compact massive objects through gravitational microlensing has become a very active field. Observations of peculiar light curves well explained as the result of the microlensing of a star by a brown dwarf have been reported by three groups. We present here the recent experimental results and we will discuss briefly their implications on Galactic structure models.

Direct dark matter search program with bolometers at the University of Tokyo

Bolometers are being developed at the University of Tokyo aiming at a search for galactic dark matter. We have succeeded in constructing a small-sized bolometer with 2.8 gram of lithium fluoride crystal with an rms energy resolution of 3.8 ke V for 60-ke V γ rays. Both lithium and fluorine are expected to be suitable for the detection of possible particle dark matter with a spin-dependent interaction like supersymmetric neutralinos. Fabrication of Neutron Transmutation Doped (NTD) germanium is also in progress to make a number of thermistors with uniform sensitivities to be used for multi-module bolometers. When the development of a full-sized detector with a total mass of order one kilogram is completed, we plan to install it in the Kamioka underground laboratory.

Analysis of direct searches for neutralino dark matter

Analysis of direct searches for neutralino dark matter

Progress report on the search for cold dark matter using ultralow-background germanium detectors at homestake

Abstract Counting rates from the two 1-kg PNL/USC ultralow-background germanium detectors are ≤0.3 counts keV −1 kg −1 d −1 between 6 and 9 keV and ∼ 2 counts keV −1 kg −1 d −1 between 4 and 6 keV. These data show a significant short-time rate dependence due to blasting and other mining operations in the Homestake good mine. The mean shift in the centroid of the gallium x-ray peak was about 50 eV over a total period of about 500 days, indicating adequate stability for a search for annual modulation of Cold Dark Matter (CDM) particles.

DIRECT VERSUS INDIRECT SEARCHES FOR NEUTRALINO DARK MATTER

Direct search for neutralino dark matter is analyzed in the framework of the minimal supersymmetric extension of the standard model, using a realistic evaluation of the neutralino relic abundance which also includes radiative corrections to the Higgs masses. Relevance of the present (Ge detectors) experimental data to set constraints on the parameters of the model is discussed and expectations for future experiments which involve neutralino-nucleus coherent processes are investigated. These results are compared to those obtained in a previous paper from indirect search data. In the present analysis particular attention is paid to the theoretical uncertainties due to the different estimates of the Higgs-nucleon coupling strength.

Search for double beta decay and dark matter in the Gotthard germanium experiment

Search for double beta decay and dark matter in the Gotthard germanium experiment

The d’alembert-euler rivalry

Jean le Rond D'Alembert and Leonhard Euler were two towering figures in the firmament of 18th century mathematical physics. They both made significant contributions to the growth and maturing of mathematics and of theoretical science. There is no question about the extraordinary genius and prolific creativity of Euler. And D'Alembert, who boldly initiated and attempted problems that interested that Swiss prodigy, often provoked Euler's unfriendly reaction. A spirit of rivalry naturally arose between the two giants. Daniel Bernoulli, another outstanding genius of the age, was also involved in some of the controversies and misunderstandings between Euler and D'Alembert. Even if profound insights and germinal ideas are sometimes credited to D'Alembert, he is usually referred to as not only creatively inferior to Euler, but even unworthy of the fame and recognition that he received. Historians of science have not been very sympathetic to D'Alembert. As specific instances of this we may mention Todhunter 's "History of Probability" in which the chapter on D'Alembert is one long enumeration of his mistakes, told in a vein that is intended to provoke pity and ridicule. In referring to the voluminous correspondence between Euler and D'Alembert in connection with the logarithm of negative numbers Cajori remarked, "D'Alembert proceeds to advance arguments of meta-physical, analytical and geometrical nature which shrouded the subject further, ''1 ignoring the fact that such arguments were quite common in 18th century discussions. Ravetz, in his s tudy of the vibrating string problem, refers to D'Alembert's "priggishness as a mathematician," and finds his opuscules "a bewildering jumble. ''2 But the dean of all D'Alembert despisers is Truesdell. This eminent scholar and historian, having edited parts of Euler's complete works, seems to have inherited his idol's antipathies for D'Alembert. Indeed they are so magnified in his writings that it is doubtful if even Euler would concur with him on all points. Here, for example, is how he describes the reading of D'Alembert's works: "One searches for the little solid matter, as a sparrow pecks out a few nutritious seeds from a d u n g h e a p a task not altogether savory. "'3 On the other hand the prodigious genius of Euler has been adequately recorded. From the fable in which Diderot is made a fool by Euler in Catherine's court 4 to E. T. Bell's fascinating sketch of Analysis Incarnate only superlat ives have been used to paint Euler 's achievements. And all the encomiums that Euler has received for his own creativity are well deserved. In this year of the 200th death anniversary of D'Alembert it will be of some interest to look a little more closely into D'Alembert's standing vis-a-vis Euler, and to see how far some of the damaging remarks against

The search for matter in its quark-gluon phase

Abstract Recent studies of the colour gauge theory of the strong interactions indicate that nuclear matter will transform into quark matter when heated or compressed by relatively modest amounts. Such matter almost certainly existed in the early Universe and is likely to be found in the interior of neutron stars. We investigate the possibility that it is formed in the collisions of relativistic heavy nuclei where it can be studied in a controlled and systematic way. As the primary cosmic ray beam provides us with heavy nuclei exceeding 106 GeV primary energy, cosmic ray experiments can possibly provide us with a first glimpse of quark-gluon plasma, a state of matter that was the main contributor to the energy of the Universe up to 105s after the Big Bang.

Terrestrial contamination in Apollo lunar samples.

The Apollo lunar samples were seen to offer a unique opportunity in the search for extraterrestrial organic matter without the ambiguity surrounding meteorite analysis due to their unknown contamination histories. The recognition that only a small amount of indigenous organic material was likely to be present in lunar samples combined with the extreme sensitivity of organic analysis methods made it clear that this opportunity could be realized only by carefully controlling the collection, processing, and analysis of the samples in order that they might remain free of significant levels of contamination. The contamination control procedures adopted are described and the analytical evidence obtained throughout the program on potential contamination sources is presented. The organic contaminants actually found in the lunar samples by the various investigators are summarized. It is shown that the program succeeded in providing investigators with samples containing less than 0.1 ppm total contamination.

The search for indigenous lunar organic matter.

Early lunar conditions are not inconsistent with the production of large quantities of prebiological organic matter now sequestered in the lunar subsurface. The absence of substantial water and organic compounds from the superficial layers of the lunar surface may not be indicative of the composition of deeper regions.

A search for meteoritic matter in atmospheric dust.

A search for meteoritic matter in atmospheric dust.