323 research outputs found
Forlì, piazza Saffi già Maggiore
No full textNella scheda viene presentato un inedito disegno (Parigi, Biblioteca del Institut de France) di Charles Percier raffigurante piazza Saffi già Maggiore di Forlì e realizzato durante il suo viaggio di ritorno da Roma a Parigi nel 1791
Large scale distribution of ultra high energy cosmic rays detected at the Pierre Auger observatory with zenith angles up to 80 degrees
No full textK. B. Barber, J. A. Bellido, S. G. Blaess, R.W. Clay, M. J. Cooper, B. R. Dawson, T. D. Grubb, T. A. Harrison, G. C. Hill, M. Malacari, P. H. Nguyen, S. J. Saffi, J. Sorokin, P. Van Bodegom are members of the Pierre Auger CollaborationWe present the results of an analysis of the large angular scale distribution of the arrival directions of cosmic rays with energy above 4 EeV detected at the Pierre Auger Observatory including for the first time events with zenith angle between 60° and 80°. We perform two Rayleigh analyses, one in the right ascension and one in the azimuth angle distributions, that are sensitive to modulations in right ascension and declination, respectively. The largest departure from isotropy appears in the 98E > 8 EeV energy bin, with an amplitude for the first harmonic in right ascension r1α = (4.4 ± 1.0) × 10-2, that has a chance probability P (≥1α) = 6.4 × 10-5, reinforcing the hint previously reported with vertical events alone.A. Aab ... K. B. Barber ... J. A. Bellido ... S. G. Blaess ... R.W. Clay ... M. J. Cooper ... B. R. Dawson ... T. D. Grubb ... T. A. Harrison ... G. C. Hill ... M. Malacari ... P. H. Nguyen ... S. J. Saffi ... J. Sorokin ... P. Van Bodegom et al. (Pierre Auger Collaboration
A search for point sources of EeV photons
No full textA. Aab, K. B. Barber, J. A. Bellido, R. W. Clay, M. J. Cooper, B. R. Dawson, T. D. Grubb, T. A. Harrison, G. C. Hill, M. Malacari, S. J. Saffi and J. Sorokin are members of The Pierre Auger CollaborationMeasurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A multivariate analysis reduces the background of hadronic cosmic rays. The search is sensitive to a declination band from –85° to +20°, in an energy range from 1017.3 eV to 1018.5 eV. No photon point source has been detected. An upper limit on the photon flux has been derived for every direction. The mean value of the energy flux limit that results from this, assuming a photon spectral index of –2, is 0.06 eV cm–2 s–1, and no celestial direction exceeds 0.25 eV cm–2 s–1. These upper limits constrain scenarios in which EeV cosmic ray protons are emitted by non-transient sources in the Galaxy.A. Aab ... K. B. Barber ... J. A. Bellido ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. D. Grubb ... T. A. Harrison ... G. C. Hill ... M. Malacari ... S. J. Saffi ... J. Sorokin ... et al. (The Pierre Auger Collaboration
Muons in air showers at the Pierre Auger Observatory: mean number in highly inclined events
No full textJ. A. Bellido, R.W. Clay, M. J. Cooper, B. R. Dawson, T. D. Grubb, T. A. Harrison, G. C. Hill, M. Malacari, S. J. Saffi, J. Sorokin are members of The Pierre Auger CollaborationWe present the first hybrid measurement of the average muon number in air showers at ultrahigh energies, initiated by cosmic rays with zenith angles between 62° and 80°. The measurement is based on 174 hybrid events recorded simultaneously with the surface detector array and the fluorescence detector of the Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulated reference profile of the lateral muon density distribution at the ground until it fits the data. A 1019 eV shower with a zenith angle of 67°, which arrives at the surface detector array at an altitude of 1450 m above sea level, contains on average (2.68±0.04±0.48(sys))×107 muons with energies larger than 0.3 GeV. The logarithmic gain dlnNμ/dlnE of muons with increasing energy between 4×1018 eV and 5×1019 eV is measured to be (1.029±0.024±0.030(sys)).A. Aab ... J. A. Bellido ... R.W. Clay ... M. J. Cooper ... B. R. Dawson ... T. D. Grubb ... T. A. Harrison ... G. C. Hill ... M. Malacari ... S. J. Saffi ... J. Sorokin ... et al. (Pierre Auger Collaboration
A targeted search for point sources of EeV neutrons
No full textA. Aab, K.B. Barber, J. A. Bellido, R. W. Clay, M. J. Cooper, B. R. Dawson, T. D. Grubb, T. A. Harrison, G. C. Hill, M. Malacari, S. J. Saffi and J. Sorokin are members of The Pierre Auger CollaborationA flux of neutrons from an astrophysical source in the Galaxy can be detected in the Pierre Auger Observatory as an excess of cosmic-ray air showers arriving from the direction of the source. To avoid the statistical penalty for making many trials, classes of objects are tested in combinations as nine "target sets," in addition to the search for a neutron flux from the Galactic center or from the Galactic plane. Within a target set, each candidate source is weighted in proportion to its electromagnetic flux, its exposure to the Auger Observatory, and its flux attenuation factor due to neutron decay. These searches do not find evidence for a neutron flux from any class of candidate sources. Tabulated results give the combined p-value for each class, with and without the weights, and also the flux upper limit for the most significant candidate source within each class. These limits on fluxes of neutrons significantly constrain models of EeV proton emission from non-transient discrete sources in the Galaxy.A. Aab ... K.B. Barber ... J. A. Bellido ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. D. Grubb ... T. A. Harrison ... G. C. Hill ... M. Malacari ... S. J. Saffi ... J. Sorokin ... et al. (The Pierre Auger Collaboration
Searches for anisotropies in the arrival directions of the highest energy cosmic rays detected by the Pierre Auger observatory
No full textJ. A. Bellido, S. G. Blaess, R. W. Clay, M. J. Cooper, B. R. Dawson, T. D. Grubb, T. A. Harrison, G. C. Hill, M. Malacari, P. H. Nguyen, S. J. Saffi, J. Sorokin, P. van Bodegom are members of The Pierre Auger CollaborationWe analyze the distribution of arrival directions of ultra-high-energy cosmic rays recorded at the Pierre Auger Observatory in 10 years of operation. The data set, about three times larger than that used in earlier studies, includes arrival directions with zenith angles up to 80°, thus covering from -90°to +45°in declination. After updating the fraction of events correlating with the active galactic nuclei (AGNs) in the Vron-Cetty and Vron catalog, we subject the arrival directions of the data with energies in excess of 40 EeV to different tests for anisotropy. We search for localized excess fluxes, self-clustering of event directions at angular scales up to 30°, and different threshold energies between 40 and 80 EeV. We then look for correlations of cosmic rays with celestial structures both in the Galaxy (the Galactic Center and Galactic Plane) and in the local universe (the Super- Galactic Plane). We also examine their correlation with different populations of nearby extragalactic objects: galaxies in the 2MRS catalog, AGNs detected by Swift-BAT, radio galaxies with jets, and the Centaurus A (Cen A) galaxy. None of the tests show statistically significant evidence of anisotropy. The strongest departures from isotropy (post-trial probability ∼1.4%) are obtained for cosmic rays with E >; 58 EeV in rather large windows around Swift AGNs closer than 130 Mpc and brighter than 1044erg s-1 (18° radius), and around the direction of Cen A (15° radius).A. Aab ... J. A. Bellido ... S. G. Blaess ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. D. Grubb ... T. A. Harrison ... G. C. Hill ... M. Malacari ... P. H. Nguyen ... S. J. Saffi ... J. Sorokin ... P. van Bodegom ... et al. (The Pierre Auger Collaboration
Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory
No full textContributing members: K.B. Barber, J.A. Bellido, R.W. Clay, M.J. Cooper, B.R. Dawson, T.D. Grubb, T.A. Harrison, A.E. Herve, G.C. Hill, V.C. Holmes, M. Malacari, S.J. Saffi, J. Sorokin, and P. Wahrlich for the University of Adelaide, Adelaide, S.A., AustraliaThe Pierre Auger Observatory in Malargüe, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10 ¹⁸eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, located near the center of the observatory site, having an optical signature comparable to that of the highest energy showers detected by the FD. This paper presents two procedures developed to retrieve the aerosol attenuation of fluorescence light from CLF laser shots. Cross checks between the two methods demonstrate that results from both analyses are compatible, and that the uncertainties are well understood. The measurements of the aerosol attenuation provided by the two procedures are currently used at the Pierre Auger Observatory to reconstruct air shower data.The Pierre Auger Collaboratio
Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory
No full textContribution Members: K.B. Barber, J.A. Bellido, R.W. Clay, M.J. Cooper, B.R. Dawson, T.A. Harrison, A.E. Herve, G.C. Hill, V.C. Holmes, M. Malacari, S.J. Saffi, J. Sorokin, P. Wahrlich for the University of Adelaide, Adelaide, S.A., AustraliaWe derive lower bounds on the density of sources of ultra-high energy cosmic rays from the lack of significant clustering in the arrival directions of the highest energy events detected at the Pierre Auger Observatory. The density of uniformly distributed sources of equal intrinsic intensity was found to be larger than ~ (0.06−5) × 10⁻⁴ Mpc⁻³ at 95% CL, depending on the magnitude of the magnetic deflections. Similar bounds, in the range (0.2−7) × 10⁻⁴ Mpc⁻³, were obtained for sources following the local matter distribution.The Pierre Auger collaboratio
Testing hadronic interactions at ultrahigh energies with air showers measured by the Pierre Auger Observatory
No full textPublished 31 October 2016Ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. Here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 EeV (E_{CM}=110-170 TeV), whose longitudinal development and lateral distribution were simultaneously measured by the Pierre Auger Observatory. The average hadronic shower is 1.33±0.16 (1.61±0.21) times larger than predicted using the leading LHC-tuned models EPOS-LHC (QGSJetII-04), with a corresponding excess of muons.A. Aab ... J. A. Bellido ... S. G. Blaess ... R.W. Clay ... M. J. Cooper ... B. R. Dawson ... T. D. Grubb ... T. A. Harrison ... G. C. Hill ... M. Malacari ... P. H. Nguyen ... S. J. Saffi ... J. Sorokin ... T. Sudholz ... P. van Bodegom ... et al. (Pierre Auger Collaboration
Depth of maximum of air-shower profiles at the Pierre Auger Observatory. I. Measurements at energies above 10(17.8) eV
No full textK.B. Barber, J.A. Bellido, S. Blaess, R.W. Clay, M.J. Cooper, B.R. Dawson, T.D. Grubb, T.A. Harrison, G. C. Hill, M. Malacari, P. Nguyen, S.J. Saffi, J. Sorokin, P. van Bodegom are members of The Pierre Auger CollaborationWe report a study of the distributions of the depth of maximum, Xmax, of extensive air-shower profiles with energies above 1017.8 eV as observed with the fluorescence telescopes of the Pierre Auger Observatory. The analysis method for selecting a data sample with minimal sampling bias is described in detail as well as the experimental cross-checks and systematic uncertainties. Furthermore, we discuss the detector acceptance and the resolution of the Xmax measurement and provide parametrizations thereof as a function of energy. The energy dependence of the mean and standard deviation of the Xmax distributions are compared to air-shower simulations for different nuclear primaries and interpreted in terms of the mean and variance of the logarithmic mass distribution at the top of the atmosphere.A. Aab ... K.B. Barber ... J.A. Bellido ... S. Blaess ... R.W. Clay ... M.J. Cooper ... B.R. Dawson ... T.D. Grubb ... T.A. Harrison ... G. C. Hill ... M. Malacari ... P. Nguyen ... S.J. Saffi ... J. Sorokin ... P. van Bodegom ... et al. ... (Pierre Auger Collaboration
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