First detection of tracks of radon progeny recoils by MIMAC

The MIMAC experiment is a $mu$-TPC matrix project for directional dark matter search. Directional detection is a strategy based on the measurement of the WIMP flux anisotropy due to the solar system motion with respect to the dark matter halo. The main purpose of MIMAC project is the measurement of the energy and the direction of nuclear recoils in 3D produced by elastic scattering of WIMPs. Since June 2012 a bi-chamber prototype is operating at the Modane underground laboratory. In this paper, we report the first ionization energy and 3D track observations of nuclear recoils produced by the radon progeny. This measurement shows the capability of the MIMAC detector and opens the possibility to explore the low energy recoil directionality signature.

e-commerce business models in the context of web3.0 paradigm

Web 3.0 promises to have a significant effect in users and businesses. It will change how people work and play, how companies use information to market and sell their products, as well as operate their businesses. The basic shift occurring in Web 3.0 is from information-centric to knowledge-centric patterns of computing. Web 3.0 will enable people and machines to connect, evolve, share and use knowledge on an unprecedented scale and in new ways that make our experience of the Internet better. Additionally, semantic technologies have the potential to drive significant improvements in capabilities and life cycle economics through cost reductions, improved efficiencies, enhanced effectiveness, and new functionalities that were not possible or economically feasible before. In this paper we look to the semantic web and Web 3.0 technologies as enablers for the creation of value and appearance of new business models. For that, we analyze the role and impact of Web 3.0 in business and we identify nine potential business models, based in direct and undirected revenue sources, which have emerged with the appearance of semantic web technologies.

MIMAC: MIcro-tpc MAtrix of Chambers for dark matter directional detection

Directional detection of non-baryonic Dark Matter is a promising search strategy for discriminating WIMP events from neutrons, the ultimate background for dark matter direct detection. This strategy requires both a precise measurement of the energy down to a few keV and 3D reconstruction of tracks down to a few mm. The MIMAC (MIcro-tpc MAtrix of Chambers) collaboration has developed in the last years an original prototype detector based on the direct coupling of large pixelized micromegas with a special developed fast self-triggered electronics showing the feasibility of a new generation of directional detectors. The first bi-chamber prototype has been installed at Modane, underground laboratory in June 2012. The first undergournd background events, the gain stability and calibration are shown. The first spectrum of nuclear recoils showing 3D tracks coming from the radon progeny is presented.

MIMAC: A micro-tpc matrix for dark matter directional detection

The dark matter directional detection opens a new field in cosmology bringing the possibility to build a map of nuclear recoils that would be able to explore the galactic dark matter halo giving access to a particle characterization of such matter and the shape of the halo. The MIMAC (MIcro-tpc MAtrix of Chambers) collaboration has developed in the last years an original prototype detector based on the direct coupling of large pixelized micromegas with a devoted fast self-triggered electronics showing the feasibility of a new generation of directional detectors. The discovery potential of this search strategy is discussed and illustrated. In June 2012, the first bi-chamber prototype has been installed at Modane Underground Laboratory (LSM) and the first underground background events, the gain stability and calibration are shown.

Directional detection of galactic dark matter

Directional detection is a promising Dark Matter search strategy. Taking advantage on the rotation of the Solar system around the galactic center through the Dark Matter halo, it allows to show a direction dependence of WIMP events that may be a powerful tool to identify genuine WIMP events as such. Directional detection strategy requires the simultaneous measurement of the energy and the 3D track of low energy recoils, which is a common challenge for all current projects of directional detectors.

Low energy electron/recoil discrimination for directional Dark Matter detection

Directional detection is a promising Dark Matter search strategy. Even though it could accommodate to a sizeable background contamination, electron/recoil discrimination remains a key and challenging issue as for direction-insensitive detectors. The measurement of the 3D track may be used to discriminate electrons from nuclear recoils. While a high rejection power is expected above 20 keV ionization, a dedicated data analysis is needed at low energy. After identifying discriminant observables, a multivariate analysis, namely a Boosted Decision Tree, is proposed, enabling an efficient event tagging for Dark Matter search. We show that it allows us to optimize rejection while keeping a rather high efficiency which is compulsory for rare event search.With respect to a sequential analysis, the rejection is about 20 times higher with a multivariate analysis, for the same Dark Matter exclusion limit.

Dependence of the structural and physical properties of Tl1-yFe2-z(Se1-xSx)2 with isovalent substitution of Se by S: decrease of TNeel with S content

The effect of selenium substitution by sulfur or tellurium in the Tl1-yFe2-zSe2 antiferromagnet was studied by x-ray and electron diffraction, magnetization and transport measurements. Tl0.8Fe1.5(Se1-xXx)2 (nominal composition) solid solutions were synthesized in the full x range (0<x<1) for X=S and up to x=0.5 for X=Te, using the sealed tube technique. No superconductivity was found down to 4.2K in the case of sulfur despite the fact that the optimal crystallographic parameters, determined by Rietveld refinements, are reached in the series (i.e. the Fe-(Se,S) interplane height and (Se,S)-Fe-(Se,S) angle for which the critical superconducting transition T$_{c}$ is usually maximal in pnictides). Quasi full Tl site (y=0.05) compared to significant alkaline deficiency (y=0.2-0.3) in analogous A1-yFe2-zSe2 (A = K, Rb, Cs), and the resulting differences in iron valency, density of states and doping, are suggested to explain this absence of superconductivity. Compounds substituted with tellurium, at least up to x=0.25, show superconducting transitions but probably due to tetragonal Fe(Se,Te) impurity phase. Transmission electron microscopy confirmed the existence of ordered iron vacancies network in the samples from the Tl$_{0.8}$Fe$_{1.5}$(Se$_{1-x}$S$_{x}$)$_{2}$ series in the form of the tetragonal $sqrt{5}$ a $times sqrt{5}$ a $times$ c superstructure (textit{I4/m}) (mixed with the orthorhombic $sqrt{2}$ a $times 2sqrt{2}$ a $times$ c form (textit{Ibam}) if the iron vacancies level is increased). The N{e}el temperature (T$_{N}$) indicating the onset of antiferromagnetism order in the $sqrt{5}$ a $times sqrt{5}$ a $times$ c supercell decreases from 450K in the selenide (x=0) to 330K in the sulfide (x=1). We finally demonstrate a direct linear relationship between $T_{Nacute{e}el}$ and the Fe-(Se,S) bond length (or Fe-(Se,S) height).

Three-dimensional track reconstruction for directional Dark Matter detection

Directional detection of Dark Matter is a promising search strategy. However, to perform such detection, a given set of parameters has to be retrieved from the recoiling tracks : direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data of forthcoming directional detectors, we present a likelihood method dedicated to 3D track reconstruction. This new analysis method is applied to the MIMAC detector. It requires a full simulation of track measurements in order to compare real tracks to simulated ones. We conclude that a good spatial resolution can be achieved, i.e. sub-mm in the anode plane and cm along the drift axis. This opens the possibility to perform a fiducialization of directional detectors. The angular resolution is shown to range between 20$^circ$ to 80$^circ$, depending on the recoil energy, which is however enough to achieve a high significance discovery of Dark Matter. On the contrary, we show that sense recognition capability of directional detectors depends strongly on the recoil energy and the drift distance, with small efficiency values (50%-70%). We suggest not to consider this information either for exclusion or discovery of Dark Matter for recoils below 100 keV and then to focus on axial directional data.

MIMAC: A micro-tpc matrix project for directional detection of dark matter

Directional detection of non-baryonic DarkMatter is a promising search strategy for discriminating WIMP events from background ones. This strategy requires both a measurement of the recoil energy down to a few keV and 3D reconstruction of tracks down to a few mm. The MIMAC project, based on a micro-TPC matrix, filled with CF4 and CHF3 is being developed. The first results of a chamber prototype of this matrix, on low energy nuclear recoils (1H and 19F) obtained with mono-energetic neutron fields are presented. The discovery potential of this search strategy is illustrated by a realistic case accessible to MIMAC.

Assessing the discovery potential of directional detection of Dark Matter

There is a worldwide effort toward the development of a large TPC (Time Projection Chamber) devoted to directional Dark Matter detection. All current projects are being designed to fulfill a unique goal : identifying weakly interacting massive particle (WIMP) as such by taking advantage of the expected direction dependence of WIMP-induced events toward the constellation Cygnus. However such proof of discovery requires a careful statistical data treatment. In this paper, the discovery potential of forthcoming directional detectors is adressed by using a frequentist approach based on the profile likelihood ratio test statistic. This allows us to estimate the expected significance of a Dark Matter detection. Moreover, using this powerful test statistic, it is possible to propagate astrophysical and experimental uncertainties in the determination of the discovery potential of a given directional detection experiment. This way, we found that a 30 kg.year CF$_4$ directional experiment could reach a 3$sigma$ sensitivity at 90% C.L. down to $10^{-5}$ pb and $3.10^{-4}$ pb for the WIMP-proton axial cross section in the most optimistic and pessimistic scenario respectively.