Search results for "Particle"
showing 10 items of 15225 documents
Response of AGATA segmented HPGe detectors to gamma rays up to 15.1MeV
2013
WOS: 000314826000009
Microbiology and atmospheric processes: research challenges concerning the impact of airborne micro-organisms on the atmosphere and climate
2011
Cet article a fait l'objet d'une discussion dans "Morris, C. E., Sands, D. C., Bardin, M., Jaenicke, R., Vogel, B., Leyronas, C., Ariya, P. A., and Psenner, R.: Microbiology and atmospheric processes: an upcoming era of research on bio-meteorology, Biogeosciences Discuss., 5, 191-212, doi:10.5194/bgd-5-191-2008, 2008."; International audience; For the past 200 years, the field of aerobiology has explored the abundance, diversity, survival and transport of micro-organisms in the atmosphere. Micro-organisms have been explored as passive and severely stressed riders of atmospheric transport systems. Recently, an interest in the active roles of these micro-organisms has emerged along with prop…
Updated measurement of the τ lepton lifetime
1997
A new measurement of the mean lifetime of the tau lepton is presented. Three different analysis methods are applied to a sample of 90000 tau pairs, collected in 1993 and 1994 with the ALEPH detector at LEP. The average of this measurement and those previously published by ALEPH is tau_tau = 290.1 +- 1.5 +- 1.1 fs.
Heavy flavour decay muon production at forward rapidity in proton--proton collisions at sqrt(s) = 7 TeV
2012
The production of muons from heavy flavour decays is measured at forward rapidity in proton-proton collisions at $\sqrt{s} = 7$ TeV collected with the ALICE experiment at the LHC. The analysis is carried out on a data sample corresponding to an integrated luminosity $L_{\rm int} = 16.5$ nb$^{-1}$. The transverse momentum and rapidity differential production cross sections of muons from heavy flavour decays are measured in the rapidity range 2.5 < y < 4, over the transverse momentum range 2 < $p_{\rm T}$ < 12 GeV/$c$. The results are compared to predictions based on perturbative QCD calculations.
On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes
2006
The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN mode…
Measurement of the AtmosphericνeSpectrum with IceCube
2015
We present a measurement of the atmospheric $\nu_e$ spectrum at energies between 0.1 TeV and 100 TeV using data from the first year of the complete IceCube detector. Atmospheric $\nu_e$ originate mainly from the decays of kaons produced in cosmic-ray air showers. This analysis selects 1078 fully contained events in 332 days of livetime, then identifies those consistent with particle showers. A likelihood analysis with improved event selection extends our previous measurement of the conventional $\nu_e$ fluxes to higher energies. The data constrain the conventional $\nu_e$ flux to be $1.3^{+0.4}_{-0.3}$ times a baseline prediction from a Honda's calculation, including the knee of the cosmic-…
Search for Extraterrestrial Point Sources of Neutrinos with AMANDA-II
2003
We present the results of a search for point sources of high energy neutrinos in the northern hemisphere using AMANDA-II data collected in the year 2000. Included are flux limits on several AGN blazars, microquasars, magnetars and other candidate neutrino sources. A search for excesses above a random background of cosmic-ray-induced atmospheric neutrinos and misreconstructed downgoing cosmic-ray muons reveals no statistically significant neutrino point sources. We show that AMANDA-II has achieved the sensitivity required to probe known TeV gamma-ray sources such as the blazar Markarian 501 in its 1997 flaring state at a level where neutrino and gamma-ray fluxes are equal.
Large numbers of cold positronium atoms created in laser-selected Rydberg states using resonant charge exchange
2016
Lasers are used to control the production of highly excited positronium atoms (Ps*). The laser light excites Cs atoms to Rydberg states that have a large cross section for resonant charge-exchange collisions with cold trapped positrons. For each trial with 30 million trapped positrons, more than 700 000 of the created Ps* have trajectories near the axis of the apparatus, and are detected using Stark ionization. This number of Ps* is 500 times higher than realized in an earlier proof-of-principle demonstration (2004 Phys. Lett. B 597 257). A second charge exchange of these near-axis Ps* with trapped antiprotons could be used to produce cold antihydrogen, and this antihydrogen production is e…
Stabilized Naked Sub-nanometric Cu Clusters within a Polymeric Film Catalyze C-N, C-C, C-O, C-S, and C-P Bond-Forming Reactions
2015
[EN] Sub-nanometric Cu clusters formed by endogenous reduction of Cu salts and Cu nanoparticles are active and selective catalysts for C−N, C−C, C−O, C−S, and C−P bond-forming reactions. Sub-nanometric Cu clusters have also been generated within a polymeric film and stored with full stability for months. In this way, they are ready to be used on demand and maintain high activity (TONs up to 104 ) and selectivity for the above reactions. A potential mechanism for the formation of the sub-nanometric clusters and their electronic nature is presented.
Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope
2012
The ANTARES telescope observes a full hemisphere of the sky all the time with a duty cycle close to 100%. This makes it well suited for an extensive observation of neutrinos produced in astrophysical transient sources. In the surrounding medium of blazars, i.e. active galactic nuclei with their jets pointing almost directly towards the observer, neutrinos may be produced together with gamma-rays by hadronic interactions, so a strong correlation between neutrinos and gamma-rays emissions is expected. The time variability information of the studied source can be obtained by the gamma-ray light curves measured by the LAT instrument on-board the Fermi satellite. If the expected neutrino flux ob…