7,140 research outputs found
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
No full textData from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the ‘hybrid’ data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction.http://www.elsevier.com/wps/find/journaldescription.cws_home/523319/description#descriptio
Symmetry characterization of unoccupied states in thick alkaline layers by spin-resolved Auger electron spectroscopy using primary excitation by circularly polarized light
No full textStoppmanns P, David R, Müller N, Heinzmann U, Grieb H, Noffke J. Symmetry characterization of unoccupied states in thick alkaline layers by spin-resolved Auger electron spectroscopy using primary excitation by circularly polarized light. Journal of physics: condensed matter. 1994;6(23):4225-4232.CVV Auger electrons emitted from K, Rb and Cs layers are studied using spin-resolved spectroscopy. Oriented 3p, 4p and 5p hole states are excited by circularly polarized radiation in normal incidence. The photon energies range from 12 to 24 eV. With all three materials, the degree and sign of the Auger electron spin polarization vary with the photon energy. As an atomic model of the Auger process predicts, and as a comparison of measurements with the calculated densities of states shows, the spin polarization is essentially determined by the symmetry of the final states reached in the primary (photo)excitation. Just above the excitation threshold, the preferential spin direction of the Auger electrons is measured to be parallel to the spin of the exciting photons corresponding to a predominantly s-like symmetry of the unoccupied final states reached by the excitation. At higher photon energies the preferential spin direction changes to be antiparallel to the photon spin, corresponding to the mainly d-like symmetry of unoccupied states reached by the excitation
Fluorescence detector optical calibration and atmospheric monitoring for the Pierre Auger experiment
No full textJune 30, 2000/Rev. January 5, 200
The Rapid Atmospheric Monitoring System of the Pierre Auger Observatory
No full textThe Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 1017 eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e. g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or "rapid") monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction
30TH INTERNATIONAL COSMIC RAY CONFERENCE Education and Outreach for the Pierre Auger Observatory
No full textAbstract: The scale and scope of the physics studied at the Auger Observatory offer significant opportunities for original outreach work. Education, outreach, and public relations of the Auger collaboration are coordinated in a task of its own whose goals are to encourage and support a wide range of efforts that link schools and the public with the Auger scientists and the science of cosmic rays, particle physics, and associated technologies. This report focuses on the impact of the collaboration in Mendoza Province, Argentina, as: the Auger Visitor Center in Malargüe that has hosted over 29,000 visitors since 2001, the Auger Celebration and a collaboration-sponsored science fair held on the Observatory campus in November 2005, the opening of the James Cronin School in Malargüe in November 2006, public lectures, school visits, and courses for science teachers. As the collaboration prepares the proposal for the northern Auger site foreseen to be in southeast Colorado, plans for a comprehensive outreach program are being developed in parallel, as described here
Discriminating potential astrophysical sources of the highest energy cosmic rays with the Pierre Auger Observatory
No full textUniversity of Adelaide participants in the Pierre Auger Collaboration: ... K. B. Barber... J. A. Bellido... R. W. Clay... B. R. Dawson... V. C. Holmes... P. Wahrlich... B. J. Whelan... M. G. WinnickWe compare the distribution of arrival directions of the highest energy cosmic rays detected by the Pierre Auger Observatory from 1 January 2004 to 31March 2009 with that of populations of potential astrophysical sources. For this purpose, we use several complementary statistical tests allowing one to describe and quantify the degree of compatibility between data and a given catalogue of sources. We applied these tests to active galactic nuclei detected in X-rays by SWIFT-BAT and to galaxies found in the HI Parkes and in the 2 Micron All-Sky Surveys.Julien Aublin, for the Pierre Auger Collaborationhttp://inspire.ornl.gov/Document/View/a22a2303-94d8-4649-8918-3000fa8eeccd?q=topic%3A%22Physics%2
The LVV Auger line shape of sulfur on copper studied by Auger photoelectron coincidence spectroscopy
No full textWe have studied the line shapes of Cu(0 0 1)-p (2× 2)S L2VV and L3VV Auger decay by means of Auger photoelectron coincidence spectroscopy. Measuring the LVV Auger spectrum in coincidence with S 2p1/2 and 2p3/2 photoelectrons respectively, we have been able to separate the two overlapping Auger spectra and determine their intrinsic line shapes. The two Auger transitions, though shifted in energy, display an identical line shape whose main features can be qualitatively understood considering a single particle approximation but are better described within a Cini-Sawatzky (CS) approach. Comparison between the experimental and the CS calculated spectra confirms that a substantial part of the Auger lines (∼20%) can be ascribed to decay events accompanied by the excitation of one additional electron-hole pair in the valence band. For the first time, the locality of the Auger process combined with the surface sensitivity of the APECS technique and its ability to separate overlapping structures are used to study Auger transitions taking place at the the surface states of a S/noble-metal interface
Copier/Coller. Ecriture et réécriture chez Voltaire
No full textIl volume raccoglie gli atti del Colloque International che è stato organizzato a Pisa dal sottoscritto insieme con i colleghi francesi Olivier Ferret e Catherine Volpilhac-Auger. Il colloquio tenutosi dal 30 giugno al 2 luglio 2005, ha riunito a Pisa i membri delle due équipes che attualmente lavorano alle Œuvres complètes di Voltaire presso la Voltaire Foundation di Oxford, attendendo l’una alla edizione dell’Essai sur les mœurs, l’altra, all’edizione delle Questions sur l’Encyclopédie. Il volume raccoglie e pubblica il testo di 17 interventi letti a Pisa. Il primo dei testi pubblicati è di Nicholas Cronk, l’attuale direttore della Voltaire Foundation di Oxford. Figura nel volume anche l’intervento del sottoscritto «Voltaire et l’ Histoire des papes de F. Bruys » (per cui vedere il titolo relativo)
Probing the surface magnetic properties via Auger-photoelectron coincidence spectroscopy
No full textAuger-photoelectron coincidence spectroscopy (APECS) via a dichroic effect is a suitable tool to study complex systems such as magnetic thin films and multilayers. We present clear evidence for such a dichroic effect in the MVV Auger line shape of Fe films on Cu(001) measured by angle resolved APECS showing final state spin selectivity (triplet vs. singlet components). Using the Fermi Golden rule and the density functional theory formalism, the Auger spectrum and its angular distributions are computed. For magnetic systems, the spin dependence of the Auger matrix elements allows one to work out the individual multiplet contributions to the Auger spectrum. For an accurate interpretation of experiments we also take into account the valence hole-hole interaction affecting the Auger line shape by the Cini-Sawatzky theory but considering a spin dependent on-site interaction U. The calculated angular distribution, in case of a non-spherical ionized core level (e.g. l=1, m=0), follows a non-trivial behavior in agreement with experiment
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