Search

Aims.Archeops is a balloon-borne experiment inspired by the Planck satellite and its high frequency instrument (HFI). It is designed to measure the cosmic microwave background (CMB) temperature anisotropies at high angular resolution (~12 arcmin) over a large fraction of the sky (around 30%) at 143, 217, 353, and 545 GHz. The Archeops 353 GHz channel consists of three pairs of polarized sensitive bolometers designed to detect the polarized diffuse emission of Galactic dust.

Context.The analysis of the time ordered data of Dark Matter experiments is becoming more and more challenging with the increase of sensitivity in the ongoing and forthcoming projects. Combined with the well-known level of background events, this leads to a rather high level of pile-up in the data. Ionization, scintillation as well as bolometric signals present common features in their acquisition timeline: low frequency baselines, random Gaussian noise, parasitic noise and signal characterized by well-defined peaks. In particular, in the case of long-lasting signals such as bolometric ones, the pile-up of events may lead to an inaccurate reconstruction of the physical signal (misidentification as well as fake events).

We present improved results on the measurement of the angular power spectrum of the Cosmic Microwave Background (CMB) temperature anisotropies using the data from the last Archeopsflight. This refined analysis is obtained by using the 6 most sensitive photometric pixels in the CMB bands centered at 143 and 217 GHz and 20% of the sky, mostly clear of foregrounds. Using two different cross-correlation methods, we obtain very similar results for the angular power spectrum. Consistency checks are performed to test the robustness of these results paying particular attention to the foreground contamination level which remains well below the statistical uncertainties. The multipole range from $\ell=10$to $\ell=700$is covered with 25 bins, confirming strong evidence for a plateau at large angular scales (the Sachs-Wolfe plateau) followed by two acoustic peaks centered around $\ell=220$and $\ell=550$respectively. These data provide an independent confirmation, obtained at different frequencies, of the Wmapfirst year results.

We present the first determination of the Galactic polarized emission at 353 GHz by Archeops. The data were taken during the Arctic night of February 7, 2002 after the balloon-borne instrument was launched by CNES from the Swedish Esrange base near Kiruna. In addition to the 143 GHz and 217 GHz frequency bands dedicated to CMB studies, Archeops had one 545 GHz and six 353 GHz bolometers mounted in three polarization–sensitive pairs that were used for Galactic foreground studies. We present maps of the $I,~Q,~U$Stokes parameters over 17% of the sky and with a 13 arcmin resolution at 353 GHz ($850~\mu{\rm m}$). They show a significant Galactic large scale polarized emission coherent on the longitude ranges $\lbrack 100,~120\rbrack$and $\lbrack 180,~200\rbrack$deg. with a degree of polarization at the level of 4–5%, in agreement with expectations from starlight polarization measurements. Some regions in the Galactic plane (Gem OB1, Cassiopeia) show an even stronger degree of polarization in the range 10–20%. These findings provide strong evidence for a powerful grain alignment mechanism throughout the interstellar medium and a coherent magnetic field coplanar to the Galactic plane. This magnetic field pervades even some dense clouds. Extrapolated to high Galactic latitude, these results indicate that interstellar dust polarized emission is the major foreground for PLANCK–HFI CMB polarization measurements.

We analyze the cosmological constraints that Archeops (Benoît et al. 2003) places on adiabatic cold dark matter models with passive power-law initial fluctuations. Because its angular power spectrum has small bins in $\ell$and large $\ell$coverage down to COBE scales, Archeops provides a precise determination of the first acoustic peak in terms of position at multipole $l_{\rm peak}=220\pm 6$, height and width. An analysis of Archeops data in combination with other CMB datasets constrains the baryon content of the Universe, $\Omega_{\rm b}h^2= 0.022^{+0.003}_{-0.004}$, compatible with Big-Bang nucleosynthesis and with a similar accuracy. Using cosmological priors obtained from recent non–CMB data leads to yet tighter constraints on the total density, e.g. $\Omega_{\rm tot}=1.00^{+0.03}_{-0.02}$using the HST determination of the Hubble constant. An excellent absolute calibration consistency is found between Archeops and other CMB experiments, as well as with the previously quoted best fit model. The spectral index nis measured to be $1.04^{+0.10}_{-0.12}$when the optical depth to reionization, τ, is allowed to vary as a free parameter, and $0.96^{+0.03}_{-0.04}$when τis fixed to zero, both in good agreement with inflation.

There is a worldwide effort toward the development of a large 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 addressed 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 taking into account astrophysical and experimental uncertainties. We show that the energy threshold and the background contamination are key experimental issues for directional detection, while angular resolution and sense recognition efficiency only mildly affect the sensitivity and the energy resolution is unimportant. This way, we found that a 30 kg.year CF4 directional experiment could reach a 3cr 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 detector performance case, respectively. [ABSTRACT FROM AUTHOR]

Directional detection is a promising dark matter search strategy. Indeed, weakly interacting massive particle (WIMP)-induced recoils would present a direction dependence toward the Cygnus constellation, while background-induced recoils exhibit an isotropic distribution in the Galactic rest frame. Taking advantage of these characteristic features, and even in the presence of a sizeable background, it has recently been shown that data from forthcoming directional detectors could lead either to a competitive exclusion or to a conclusive discovery, depending on the value of the WIMP-nucleon cross section. However, it is possible to further exploit these upcoming data by using the strong dependence of the WIMP signal with: the WIMP mass and the local WIMP velocity distribution. Using a Markov chain Monte Carlo analysis of recoil events, we show for the first time the possibility to constrain the unknown WIMP parameters, both from particle physics (mass and cross section) and Galactic halo (velocity dispersion along the three axis), leading to an identification of non-baryonic dark matter. [ABSTRACT FROM AUTHOR]

Aims. Archeops is a balloon-borne experiment, mainly designed to measure the Cosmic Microwave Background (CMB) temperature anisotropies at high angular resolution (~12?arcmin). By-products of the mission are shallow sensitivity maps over a large fraction of the sky (about 30%) in the millimetre and submillimetre range at 143, 217, 353 and 545?GHz. From these maps, we produce a catalog of bright submillimetre point sources.Methods. We present in this paper the processing and analysis of the Archeops point sources. Redundancy across detectors is the key factor allowing us to distinguish glitches from genuine point sources in the 20?independent maps.Results. We look at the properties of the most reliable point sources, totalling 304. Fluxes range from 1 to 10?000?Jy (at the frequencies covering 143 to 545?GHz). All sources are either planets?(2) or of galactic origin. The longitude range is from 75 to 198?degrees. Some of the sources are associated with the well-known Lynds Nebulae and HII?compact regions in the galactic plane. A large fraction of the sources have an IRAS counterpart. Except for Jupiter, Saturn, the Crab and Cas?A, all sources show a dust-emission-like modified blackbody emission spectrum. Temperatures cover a range from 7 to 27?K. For the coldest sources (T < 10?K), a steep ???emissivity law is found with a surprising ? ~ 3 to?4. An inverse relationship between T and ? is observed. The number density of sources at 353?GHz with flux brighter than 100?Jy is of the order of 1?per?degree of Galactic longitude. These sources will provide a strong check for the calibration of the Planck HFI focal plane geometry as a complement to planets. These very cold sources observed by Archeops should be prime targets for mapping observations by the Akari and Herschel space missions and ground-based observatories.

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at http://www-lphe.epfl.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects towards the gridification of GATE and its extension to other domains such as dosimetry are also discussed.

Proven or suspected intestinal tuberculosis was diagnosed in 23(46 per cent) of 50 patients with smear-positive, cavitatlng pulmonary tuberculosis. The diagnosis was regarded as proven in patients and suspected in the remaining nine. The frequency of proven gastrointestinal disease increased with the severity of the pulmonary tuberculosis. Small intestinal disease was encountered in only two patients. Small mucosal lesions in the caecum were the most commonly detected pathological features. Colonoscopy was of particular value in establishing the diagnosis, which could not be predicted from the patients' abdominal signs or gastrointestinal symptoms.

We investigate the capability of directional detectors to probe neutralino dark matter in the minimal supersymmetric standard model and the next-to-minimal supersymmetric standard model with parameters defined at the weak scale. We show that directional detectors such as the future MIMAC detector will probe spin-dependent dark matter scattering on nucléons that are beyond the reach of current spin-independent detectors. The complementarity between indirect searches, in particular, using gamma rays from dwarf spheroidal galaxies, spin-dependent and spin-independent direct search techniques is emphasized. We comment on the impact of the negative results on squark searches at the LHC. Finally, we investigate how the fundamental parameters of the models can be constrained in the event of a dark matter signal. [ABSTRACT FROM AUTHOR]