Search results for "Universe"
showing 10 items of 2171 documents
A method for detection of muon induced electromagnetic showers with the ANTARES detector
2012
The primary aim of ANTARES is neutrino astronomy with upward going muons created in charged current muon neutrino interactions in the detector and its surroundings. Downward going muons are background for neutrino searches. These muons are the decay products of cosmic-ray collisions in the Earths atmosphere far above the detector. This paper presents a method to identify and count electromagnetic showers induced along atmospheric muon tracks with the ANTARES detector. The method is applied to both cosmic muon data and simulations and its applicability to the reconstruction of muon event energies is demonstrated. © 2012 Elsevier B.V. All rights reserved.
Search for point-like sources of ultra-high energy neutrinos at the pierre auger observatory and improved limit on the diffuse flux of tau neutrinos
2012
The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy Eν between 1017 eV and 1020 eV from point-like sources across the sky south of +55º and north of −65º declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth’s crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of ∼3.5 years of a full surface detector array for the Earth-skimming channel and ∼2 years…
Search for ultrahigh energy neutrinos in highly inclined events at the Pierre Auger Observatory
2011
Erratum: Phys. Rev. D 85, 029902(E) (2012) [http://dx.doi.org/10.1103/PhysRevD.85.029902]
The galaxy power spectrum take on spatial curvature and cosmic concordance
2020
The concordance of the $\Lambda$CDM cosmological model in light of current observations has been the subject of an intense debate in recent months. The 2018 Planck Cosmic Microwave Background (CMB) temperature anisotropy power spectrum measurements appear at face value to favour a spatially closed Universe with curvature parameter $\Omega_K<0$. This preference disappears if Baryon Acoustic Oscillation (BAO) measurements are combined with Planck data to break the geometrical degeneracy, although the reliability of this combination has been questioned due to the strong tension present between the two datasets when assuming a curved Universe. Here, we approach this issue from yet another point…
Particle energization in colliding subcritical collisionless shocks investigated in the laboratory
2022
Context. Colliding collisionless shocks appear across a broad variety of astrophysical phenomena and are thought to be possible sources of particle acceleration in the Universe. Aims. The main goal of our experimental and computational work is to understand the effect of the interpenetration between two subcritical collisionless shocks on particle energization. Methods. To investigate the detailed dynamics of this phenomenon, we performed a dedicated laboratory experiment. We generated two counter-streaming subcritical collisionless magnetized shocks by irradiating two Teflon (C2F4) targets with 100 J, 1 ns laser beams on the LULI2000 laser facility. The interaction region between the plasm…
Macroecological properties of ammonites : spatial distribution, phylogeny, and faunal similarity
2016
The present work, which lies between macroecology and macroevolution, focuses on the spatio-temporal dynamics of early Pliensbachian ammonites of the western Tethys. Two main questions are addressed: how does inter-assemblage compositional similarity decrease with geographical distance? What is the relationship between species range size and phylogeny, species duration and latitudinal position?Ammonite dispersal dynamics are studied through a multi-scale Similarity Distance Decay analysis. We show that their long-distance dispersal is facilitated when the environment is more homogeneous and that it is not related to their morphology. This suggests that their long-distance dispersal occurred…
Le gisement pléistocène moyen récent de Romain-la-Roche (Doubs, France) : synthèse biostratigraphique et paléoécologique
2010
Accessible à l'adresse : http://www.ville-ge.ch/mhng/paleo/paleo-pdf/29-2/pal_29_2_07_20.pdf; International audience; L'aven de Romain-la-Roche est une cavité karstique ayant fonctionné comme un piège naturel dans lequel sont tombés de nombreux grands animaux, et où divers petits vertébrés ont été amenés en tant que proies d'oiseaux rapaces. Le gisement a été fouillé de 1980 à 1991 par Patrick Paupe et son équipe, qui y a recueilli 52 espèces de mammifères (plus de 10 000 restes déterminables), au moins 13 espèces d'oiseaux, deux de reptiles, une d'amphibien, deux espèces de poissons et des gastéropodes indéterminés. Les espèces de mammifères présentes sont pour 34,6 % des rongeurs (3975 re…
Analyse odontométrique comparée de populations du campagnol des neiges Chionomys nivalis (Martins, 1842) (Rodentia, Arvicolinae).
2007
14 pages; La morphométrie comparée de la première molaire inférieure (M1) de onze populations du campagnol des neiges Chionomys nivalis (Rodentia, Arvicolinae) (Martins, 1842) du Pléistocène supérieur et de l'Holocène de France, d'Allemagne et de Roumanie, montre une nette différenciation morphologique entre les populations de ces trois pays, exprimée par un gradient morphologique est-ouest. A l'échelle du pays, des divergences morphologiques, plus modérées, sont observées, en particulier chez les populations de France et des Carpates méridionales et occidentales.
INTEGRAL/SPI ground calibration
2003
Three calibration campaigns of the spectrometer SPI have been performed before launch in order to determine the instrument characteristics, such as the effective detection area, the spectral resolution and the angular resolution. Absolute determination of the effective area has been obtained from simulations and measurements. At 1 MeV, the effective area is 65 cm^2 for a point source on the optical axis, the spectral resolution ~2.3 keV. The angular resolution is better than 2.5 deg and the source separation capability about 1 deg. Some temperature dependant parameters will require permanent in-flight calibration.
Origin of atmospheric lead in Johannesburg, South Africa
2006
International audience; The origin of lead in the atmosphere of Johannesburg, South Africa was investigated on the basis of elemental and lead isotopic analyses of coals, mine dumps, gasoline, and about 30 epiphytic lichen samples. Lead predominantly comes from automotive exhausts in urban and suburban areas, as leaded antiknock additives were still in use in South Africa at the time of the study. Although dust emissions from the numerous mine-tailing dumps were expected to contribute significantly to the heavy metal budget, the southern townships that are surrounded by the dumps (such as Soweto and other historically Black residential areas) do not appear to be more than partially influenc…