9,837 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
Multimessenger Studies with the Pierre Auger Observatory
No full textThe Pierre Auger Observatory, the world’s largest ultra-high-energy (UHE) cosmic ray (CR) detector, plays a crucial role in multi-messenger astroparticle physics with its high sensitivity to UHE photons and neutrinos. Recent Auger Observatory studies have set stringent limits on the diffuse and point-like fluxes of these particles, enhancing constraints on dark-matter models and UHECR sources. Although no temporal coincidences of neutrinos or photons with LIGO/Virgo gravitational wave events have been observed, competitive limits on the energy radiated in these particles have been established, particularly from the GW170817 binary neutron star merger. Additionally, correlations between the arrival directions of UHECRs and high-energy neutrinos have been explored using data from the IceCube Neutrino Observatory, ANTARES, and the Auger Observatory, providing additional neutrino flux constraints. Efforts to correlate UHE neutron fluxes with gamma-ray sources within our galaxy continue, although no significant excesses have been found. These collaborative and multi-faceted efforts underscore the pivotal role of the Auger Observatory in advancing multi-messenger astrophysics and probing the most extreme environments of the Universe
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
The Auger-hole method : a field measurement of the hydraulic conductivity of soil below the water table
No full textX-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density study of ternary chalcogenide glasses based on Ge-Se and Ge-S
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Glasses of the systems Ge-Se-X (X = Ga, Sn, Bi, Sb), Ge-S-Y (Y = Ag, Ga, Sn, Bi) and Se-S have been examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), density and differential scanning calorimetry (DSC). Two of the compositions, GeSe2 and (GeSe2)92Ga8, have also been examined by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). The emphasis of the XPS measurements was on the changes in the binding energies with composition of the core peaks of the glasses, and on the plasmon energy losses from the L3M4,5M4,5 Auger lines of Se and Ge. It was found that there were small shifts in the binding energies of the core peaks on substitution but the plasmon energy changed markedly with composition. For the XRD measurements, the focus was on two features : (a) to ensure that the samples prepared were truely amorphous and (b) to confirm the presence of the first sharp diffraction peak (FSDP) on the interference functions. The density measurements showed that the addition of the third element (X or
Y) to the binary resulted in an increase in the relative density except for one system, Ge-Se-Sn, which showed the opposite behaviour. The DSC measurements showed that the addition of the third element to the binary resulted in a decrease in the glass transition temperatures. The EXAFS and XANES measurements of GeSe2 and (GeSe2)92Ga8 glasses showed that there was very little change in the local order around the Ge atom in GeSe2 glass with increase in temperature and that the local order around the Ge atom changes on alloying GeSe2 with Ga. Correlations between parameters and measured properties of the ternary alloys have been investigated. It has been found that the parameter , the average coordination number, correlates well with certain structural properties but badly with others. Suggestions are made for an alternative to .This study was funded by the British Council
Hollow Auger.
No full textPatent for a new and improved hollow auger. This design "consists in an adjustable hollow auger and an adjustable fore-auger, which are combined together for use with an ordinary brace, and constructed in such a manner that when applied to use the end of the spoke or other article is first beveled by the fore-auger, and the tenon then formed by the hollow auger. The cutters of the fore-auger are formed upon pivoted arms, which are automatically released, and then thrown open by a spring when the spoke is pointed, in order to give opportunity for the hollow auger to act" (lines 16-28)
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Measurement of the proton-air cross-section at TeV with the Pierre Auger Observatory
No full textWe report a measurement of the proton-air cross section for particle production at the center-of-mass energy per nucleon of 57 TeV. This is derived from the distribution of the depths of shower maxima observed with the Pierre Auger Observatory: systematic uncertainties are studied in detail. Analyzing the tail of the distribution of the shower maxima, a proton-air cross section of [505 {+-} 22(stat){sub -36}{sup +28}(syst)] mb is found
Observation of EarthCARE Laser Emissions with the Pierre Auger Observatory
No full textThe Atmospheric Lidar (ATLID) onboard the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) satellite has been repeatedly observed by the Fluorescence Detector of the Pierre Auger Observatory. Side-scattered ultraviolet light from ATLID laser pulses is recorded by the Auger fluorescence telescopes, which are primarily designed to measure the longitudinal development of extensive air showers initiated by ultra-high-energy cosmic rays. These measurements enable a precise reconstruction of the atmospheric trajectory of the laser beam over the Observatory and provide a unique opportunity for systematic studies of the local atmospheric aerosol content. Furthermore, EarthCARE laser tracks can be observed at the Telescope Array Experiment in the USA within a few days during the same moon cycle, opening the possibility for a direct cross-calibration of the energy scales of the two cosmic-ray observatories. We present first reconstruction results from ATLID observations following EarthCARE*s launch in 2024. These results highlight the potential of satellite-based lidar observations to support calibration and atmospheric characterization efforts at the Pierre Auger Observatory
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