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Opis: The data collected with the Pierre Auger Observatory have led to a number of surprising discoveries. While a strong suppression of the particle flux at the highest energies has been established unambiguously, the dominant physics processes related to this suppression could not be identified. Within the energy range covered by fluorescence detector observations with sufficient statistics, an unexpected change of the depth of maximum distribution is found. Using LHC-tuned interaction models these observations can be understood as a correlated change of the fluxes of different mass groups. On the other hand, they could also indicate a change of hadronic interactions above the energy of the ankle. Complementing the water Cherenkov detectors of the surface array with scintillator detectors will, mainly through the determination of the muonic shower component, extend the composition sensitivity of the Auger Observatory into the flux suppression region. The upgrade of the Auger Observatory will allow us to estimate the primary mass of the highest energy cosmic rays on a shower-by-shower basis. In addition to measuring the mass composition the upgrade will open the possibility to search for light primaries at the highest energies, to perform composition-selected anisotropy studies, and to search for new phenomena including unexpected changes of hadronic interactions. After introducing the physics motivation for upgrading the Auger Observatory the planned detector upgrade is presented. In the second part of the contribution the expected performance and improved physics sensitivity of the upgraded Auger Observatory are discussed.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, elemental composition sensitivity, Auger upgrade (AugerPrime), muonic shower component, scintillator detectors
Objavljeno v RUNG: 03.03.2016; Ogledov: 5516; Prenosov: 226
Celotno besedilo (659,02 KB)

Opis: The Auger Engineering Radio Array, an extension of the Pierre Auger Observatory with antennas in the MHz range, requires to monitor the atmospheric conditions, which have a large influence on the radio emission of air showers. In particular, amplified signals up to an order of magnitude have been detected as an affect of thunderstorms. For a more detailed investigation and more generally, for detecting thunderstorms, a new lightning detection system has been installed at the Pierre Auger Observatory in Argentina. In addition, an electric-field mill measures the field strength on ground level at the antenna array. With these measurements, data periods affected by thunderstorms can be identified. Additionally, a lightning trigger for the water-Cherenkov detectors was developed to read out individual stations when a lightning was detected nearby. With these data, a possible correlation between the formation of lightning and cosmic rays can be investigated even at low energies of about 10[sup]15 eV. The structure and functionality of the lightning detection are described and first data analyses are shown.
Ključne besede: Pierre Auger Observatory, Auger Engineering Radio Array, atmospheric monitoring, lightning detectors
Objavljeno v RUNG: 03.03.2016; Ogledov: 5757; Prenosov: 200
Celotno besedilo (1,10 MB)

Opis: We present a combined fit of both flux and composition of ultra-high energy cosmic rays as measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 × 10[sup]18 eV, i.e. the region of the all-particle spectrum above the so-called “ankle” feature. A simple astrophysical model consisting of identical sources has been adopted, where nuclei are injected with a rigidity dependent mechanism and the sources are uniformly distributed in a comoving volume. The fit results suggest a source model characterized by relatively low maximum injection energies and hard spectral indices. The impact of different sources of systematic uncertainties in the above result is discussed.
Ključne besede: Pierre Auger Observatory, ultra-high energy cosmic rays, energy spectrum, elemental composition, combined data fit
Objavljeno v RUNG: 03.03.2016; Ogledov: 5787; Prenosov: 234
Celotno besedilo (704,98 KB)

Opis: With hybrid data of the Pierre Auger Observatory it is possible to measure the cross section of proton-air collisions at energies far beyond the reach of the LHC. Since the first measurement by the Pierre Auger Collaboration the event statistics has increased significantly. The proton-air cross section is now estimated in the two energy intervals in lg(E/eV) from 17.8 to 18 and from 18 to 18.5. These energies are chosen so that they maximise the available event statistics and at the same time lie in the region most compatible with a significant primary proton fraction. Of these data, only the 20% of most proton-like events are considered for the measurement. Furthermore, with a new generation of hadronic interaction models which have been tuned to LHC data, the model-dependent uncertainties of the measurement are re-visited.
Ključne besede: Pierre Auger Observatory, extensive air showers, proton-air cross section, hadronic interaction models
Objavljeno v RUNG: 03.03.2016; Ogledov: 5669; Prenosov: 199
Celotno besedilo (114,02 KB)

Opis: The azimuthal asymmetry in the risetime of signals in Auger surface detector stations is a source of information on shower development. The azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. The magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable sensitive to the mass composition of cosmic rays above 3 × 10[sup]18 eV. By comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (QGSJetII- 04 and Epos-LHC) an indication that the mean cosmic-ray mass increases with energy, as has been inferred from other studies. However the absolute values derived for the mass are dependent on the shower model and on the range of distance from the shower core selected. Thus the method has uncovered further deficiencies in our understanding of shower modelling that must be resolved before the mass composition can be inferred from (sec θ)max.
Ključne besede: Pierre Auger Observatory, Surface Detector, risetime of detector signal, azimuthal asymmetry, extensive air showers
Objavljeno v RUNG: 03.03.2016; Ogledov: 5847; Prenosov: 199
Celotno besedilo (243,04 KB)