6 research outputs found
Constraining models for the origin of ultra-high-energy cosmic rays with a novel combined analysis of arrival directions, spectrum, and composition data measured at the Pierre Auger Observatory
The combined fit of the measured energy spectrum and shower maximum depth distributions of ultra-high-energy cosmic rays is known to constrain the parameters of astrophysical models with homogeneous source distributions. Studies of the distribution of the cosmic-ray arrival directions show a better agreement with models in which a fraction of the flux is non-isotropic and associated with the nearby radio galaxy Centaurus A or with catalogs such as that of starburst galaxies. Here, we present a novel combination of both analyses by a simultaneous fit of arrival directions, energy spectrum, and composition data measured at the Pierre Auger Observatory. The model takes into account a rigidity-dependent magnetic field blurring and an energy-dependent evolution of the catalog contribution shaped by interactions during propagation. We find that a model containing a flux contribution from the starburst galaxy catalog of around 20% at 40 EeV with a magnetic field blurring of around 20° for a rigidity of 10 EV provides a fair simultaneous description of all three observables. The starburst galaxy model is favored with a significance of 4.5σ (considering experimental systematic effects) compared to a reference model with only homogeneously distributed background sources. By investigating a scenario with Centaurus A as a single source in combination with the homogeneous background, we confirm that this region of the sky provides the dominant contribution to the observed anisotropy signal. Models containing a catalog of jetted active galactic nuclei whose flux scales with the γ-ray emission are, however, disfavored as they cannot adequately describe the measured arrival directions
AugerPrime surface detector electronics
Operating since 2004, the Pierre Auger Observatory has led to major advances in our understanding of the ultra-high-energy cosmic rays. The latest findings have revealed new insights that led to the upgrade of the Observatory, with the primary goal of obtaining information on the primary mass of the most energetic cosmic rays on a shower-by-shower basis. In the framework of the upgrade, called AugerPrime, the 1660 water-Cherenkov detectors of the surface array are equipped with plastic scintillators and radio antennas, allowing us to enhance the composition sensitivity. To accommodate new detectors and to increase experimental capabilities, the electronics is also upgraded. This includes better timing with up-to-date GPS receivers, higher sampling frequency, increased dynamic range, and more powerful local processing of the data. In this paper, the design characteristics of the new electronics and the enhanced dynamic range will be described. The manufacturing and test processes will be outlined and the test results will be discussed. The calibration of the SD detector and various performance parameters obtained from the analysis of thefirst commissioning data will also be presented
Testing Hadronic-Model Predictions of Depth of Maximum of Air-Shower Profiles and Ground-Particle Signals using Hybrid Data of the Pierre Auger Observatory
International audienceWe test the predictions of hadronic interaction models regarding the depth of maximum of air-shower profiles, , and ground-particle signals in water-Cherenkov detectors at 1000 m from the shower core, , using the data from the fluorescence and surface detectors of the Pierre Auger Observatory. The test consists in fitting the measured two-dimensional (, ) distributions using templates for simulated air showers produced with hadronic interaction models EPOS-LHC, QGSJet II-04, Sibyll 2.3d and leaving the scales of predicted and the signals from hadronic component at ground as free fit parameters. The method relies on the assumption that the mass composition remains the same at all zenith angles, while the longitudinal shower development and attenuation of ground signal depend on the mass composition in a correlated way. The analysis was applied to 2239 events detected by both the fluorescence and surface detectors of the Pierre Auger Observatory with energies between to eV and zenith angles below . We found, that within the assumptions of the method, the best description of the data is achieved if the predictions of the hadronic interaction models are shifted to deeper values and larger hadronic signals at all zenith angles. Given the magnitude of the shifts and the data sample size, the statistical significance of the improvement of data description using the modifications considered in the paper is larger than even for any linear combination of experimental systematic uncertainties
Demonstrating Agreement between Radio and Fluorescence Measurements of the Depth of Maximum of Extensive Air Showers at the Pierre Auger Observatory
International audienceWe show, for the first time, radio measurements of the depth of shower maximum () of air showers induced by cosmic rays that are compared to measurements of the established fluorescence method at the same location. Using measurements at the Pierre Auger Observatory we show full compatibility between our radio and the previously published fluorescence data set, and between a subset of air showers observed simultaneously with both radio and fluorescence techniques, a measurement setup unique to the Pierre Auger Observatory. Furthermore, we show radio resolution as a function of energy and demonstrate the ability to make competitive high-resolution measurements with even a sparse radio array. With this, we show that the radio technique is capable of cosmic-ray mass composition studies, both at Auger and at other experiments
Testing hadronic-model predictions of depth of maximum of air-shower profiles and ground-particle signals using hybrid data of the Pierre Auger Observatory
We test the predictions of hadronic interaction models regarding the depth of maximum of air-shower
profiles, Xmax , and ground-particle signals in water-Cherenkov detectors at 1000 m from the shower core,
Sð1000Þ, using the data from the fluorescence and surface detectors of the Pierre Auger Observatory. The
test consists of fitting the measured two-dimensional (Sð1000Þ, Xmax ) distributions using templates for
simulated air showers produced with hadronic interaction models E pos-LHC , QGSJ et-II -04, SIBYLL 2.3d and
leaving the scales of predicted Xmax and the signals from hadronic component at ground as free-fit
parameters. The method relies on the assumption that the mass composition remains the same at all zenith
angles, while the longitudinal shower development and attenuation of ground signal depend on the mass
composition in a correlated way. The analysis was applied to 2239 events detected by both the fluorescence
and surface detectors of the Pierre Auger Observatory with energies between 10 18.5 eV to 10 19.0 eV and
zenith angles below 60°. We found, that within the assumptions of the method, the best description of the
data is achieved if the predictions of the hadronic interaction models are shifted to deeper Xmax values and
larger hadronic signals at all zenith angles. Given the magnitude of the shifts and the data sample size, the
statistical significance of the improvement of data description using the modifications considered in the
paper is larger than 5σ even for any linear combination of experimental systematic uncertainties