66 research outputs found
Spectral calibration of the fluorescence telescopes of the Pierre Auger Observatory
No full textAbstract not availableA. 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 … P.H. Nguyen … S.J. Saffi … T. Sudholz … P. van Bodegom … [et al.] (The Pierre Auger Collaboratio
Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory
No full textPublished April 20, 2017We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 ⋅ 1018 eV, i.e. the region of the all-particle spectrum above the so-called "ankle" feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated through a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies, hard spectra and heavy chemical composition. We also show that uncertainties about physical quantities relevant to UHECR propagation and shower development have a non-negligible impact on the fit results.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 … P.H. Nguyen … S.J. Saffi … J. Sorokin … T. Sudholz … P. van Bodegom … et al. (The Pierre Auger Collaboration
Impact of atmospheric effects on the energy reconstruction of air showers observed by the surface detectors of the Pierre Auger Observatory
No full textAtmospheric conditions, such as the pressure (P), temperature (T) or air density (ρ∞P/T), affect the development of extended air showers initiated by energetic cosmic rays. We study the impact of the atmospheric variations on the reconstruction of air showers with data from the arrays of surface detectors of the Pierre Auger Observatory, considering separately the one with detector spacings of 1500m and the one with 750m spacing. We observe modulations in the event rates that are due to the influence of the air density and pressure variations on the measured signals, from which the energy estimators are obtained. We show how the energy assignment can be corrected to account for such atmospheric effects.A. Aab … J.A. Bellido … S.G. Blaess … B.R. Dawson … T.D. Grubb … T.A. Harrison … G.C. Hill … P.H. Nguyen … S.J Saffi … J. Sorokin … P. van Bodegom … [et al.] (The Pierre Auger collaboration
Search for ultrarelativistic magnetic monopoles with the Pierre Auger observatory
No full textWe present a search for ultrarelativistic magnetic monopoles with the Pierre Auger observatory. Such particles, possibly a relic of phase transitions in the early Universe, would deposit a large amount of energy along their path through the atmosphere, comparable to that of ultrahigh-energy cosmic rays (UHECRs). The air-shower profile of a magnetic monopole can be effectively distinguished by the fluorescence detector from that of standard UHECRs. No candidate was found in the data collected between 2004 and 2012, with an expected background of less than 0.1 event from UHECRs. The corresponding 90% confidence level (C.L.) upper limits on the flux of ultrarelativistic magnetic monopoles range from 10−19(cm2 sr s)−1 for a Lorentz factor γ=109 to 2.5×10−21(cm2 sr s)−1 for γ=1012. These results—the first obtained with a UHECR detector—improve previously published limits by up to an order of magnitude.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
Inferences on mass composition and tests of hadronic interactions from 0.3 to 100 EeV using the water-Cherenkov detectors of the Pierre Auger Observatory
No full textWe present a new method for probing the hadronic interaction models at ultrahigh energy and extracting details about mass composition. This is done using the time profiles of the signals recorded with the water- Cherenkov detectors of the Pierre Auger Observatory. The profiles arise from a mix of the muon and electromagnetic components of air showers. Using the risetimes of the recorded signals, we define a new parameter, which we use to compare our observations with predictions from simulations. We find, first, inconsistencies between our data and predictions over a greater energy range and with substantially more events than in previous studies. Second, by calibrating the new parameter with fluorescence measurements from observations made at the Auger Observatory, we can infer the depth of shower maximum Xmax for a sample of over 81,000 events extending from 0.3 to over 100 EeV. Above 30 EeV, the sample is nearly 14 times larger than what is currently available from fluorescence measurements and extending the covered energy range by half a decade. The energy dependence of 〈Xmax〉 is compared to simulations and interpreted in terms of the mean of the logarithmic mass. We find good agreement with previous work and extend the measurement of the mean depth of shower maximum to greater energies than before, reducing significantly the statistical uncertainty associated with the inferences about mass composition.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 … P.H. Nguyen … S.J. Saffi … T. Sudholz … P. van Bodegom … et al. (Pierre Auger Collaboration)
Multi-Messenger Physics With the Pierre Auger Observatory
No full textAn overview of the multi-messenger capabilities of the Pierre Auger Observatory is presented. The techniques and performance of searching for Ultra-High Energy neutrinos, photons and neutrons are described. Some of the most relevant results are reviewed, such as stringent upper bounds that were placed to a flux of diffuse cosmogenic neutrinos and photons, bounds placed on neutrinos emitted from compact binary mergers that were detected by LIGO and Virgo during their first and second observing runs, as well as searches for high energy photons and neutrons from the Galactic center that constrain the properties of the putative Galactic PeVatron, observed by the H.E.S.S. collaboration. The observation of directional correlations between ultra-high energy cosmic rays and either high energy astrophysical neutrinos or specific source populations, weighted by their electromagnetic radiation, are also discussed. They constitute additional multi-messenger approaches aimed at identifying the sources of high energy cosmic rays.The Pierre Auger Collaboration … Karl-Heinz Kampert … J.M. Albury … J.A. Bellido ... S.G. Blaess … R.W. Clay … M.J. Cooper … B.R. Dawson … J.A. Day … T.D. Grubb … T.A. Harrison … V.M. Harvey … G.C. Hill … B.C. Manning … P.H. Nguyen … S.J. Saffi … T. Sudholz … P. van Bodegom … et al
Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory
No full textPublished June 13, 2017We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80◦ and energies in excess of 4 EeV (4 × 10¹⁸ eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providing directional information on any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p-values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10⁻⁵ in the case of the angular power spectrum, and 2.5 × 10⁻³in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.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 … P.H. Nguyen … S.J. Saffi … J. Sorokin … T. Sudholz … P. van Bodegom … et al. (The Pierre Auger Collaboration
Muon counting using silicon photomultipliers in the AMIGA detector of the Pierre Auger observatory
No full textPublished: March 3, 2017AMIGA (Auger Muons and Infill for the Ground Array) is an upgrade of the Pierre Auger Observatory designed to extend its energy range of detection and to directly measure the muon content of the cosmic ray primary particle showers. The array will be formed by an infill of surface water-Cherenkov detectors associated with buried scintillation counters employed for muon counting. Each counter is composed of three scintillation modules, with a 10m2 detection area per module. In this paper, a new generation of detectors, replacing the current multi-pixel photomultiplier tube (PMT) with silicon photo sensors (aka. SiPMs), is proposed. The selection of the new device and its front-end electronics is explained. A method to calibrate the counting system that ensures the performance of the detector is detailed. This method has the advantage of being able to be carried out in a remote place such as the one where the detectors are deployed. High efficiency results, i.e. 98% efficiency for the highest tested overvoltage, combined with a low probability of accidental counting (~2 %), show a promising performance for this new system.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. (The Pierre Auger collaboration
Evidence for a mixed mass composition at the ‘ankle’ in the cosmic-ray spectrum
No full textWe report a first measurement for ultrahighenergy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electro- magnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncer- tainties in hadronic event generators. The observed correlation in the energy range around the ‘ankle’ at lg(E/eV) = 18.5–19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A > 4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavoredas the sole explanation of the ultrahigh-energy cosmic-ray flux at EarthPierre Auger Collaboration ... P.L.Biermann ... S.G. Blaess ... R.W.Clay ... M.J. Cooper ... B.R. Dawson ... et.al
The Pierre Auger Cosmic Ray Observatory
No full textThe Pierre Auger Observatory, located on a vast, high plain in western Argentina, is the world׳s largest cosmic ray observatory. The objectives of the Observatory are to probe the origin and characteristics of cosmic rays above 10¹⁷ eV and to study the interactions of these, the most energetic particles observed in nature. The Auger design features an array of 1660 water Cherenkov particle detector stations spread over 3000 km² overlooked by 24 air fluorescence telescopes. In addition, three high elevation fluorescence telescopes overlook a 23.5 km², 61-detector infilled array with 750 m spacing. The Observatory has been in successful operation since completion in 2008 and has recorded data from an exposure exceeding 40,000 km² sr yr. This paper describes the design and performance of the detectors, related subsystems and infrastructure that make up the Observatory.A. Aab ... K.B. Barber ... J.A. Bellido ... S.G. Blaess ... R.W. Clay ... M.J. Cooper ... B.R. Dawson ... T.D. Grubb ... G.C. Hill ... M. Malacari ... P.H.Nguyen ... S.J. Saffi ... A.G.K. Smith ... J. Sorokin ... P. van Bodegom, ... N.Wild ... et al. (Pierre Auger Collaboration
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