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Opis: The large-scale distribution of arrival directions of high-energy cosmic rays is a key observable in attempts to understanding their origin. The dipole and quadrupole moments are of special interest in revealing potential anisotropies. An unambiguous measurement of these moments as well as of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Pierre Auger Observatory and the Telescope Array above 10[sup]19 eV has been performed. Thanks to the full-sky coverage, the measurement of the dipole moment reported in this study does not rely on any assumption on the underlying flux of cosmic rays. As well, the resolution on the quadrupole and higher order moments is the best ever obtained. The resulting multipolar expansion of the flux of cosmic rays allows a series of anisotropy searches to be performed, and in particular to report on the first angular power spectrum of cosmic rays. This allows a comprehensive description of the angular distribution of cosmic rays above 10[sup]19 eV.
Ključne besede: Pierre Auger Observatory, Telescope Array, high-energy cosmic rays, large-scale anisotropies, angular power spectrum
Objavljeno v RUNG: 08.03.2016; Ogledov: 5717; Prenosov: 193
Celotno besedilo (462,61 KB)

Opis: We have conducted three searches for correlations between ultra-high energy cosmic rays detected by the Telescope Array and the Pierre Auger Observatory, and high-energy neutrino candidate events from IceCube. Two cross-correlation analyses with UHECRs are done: one with 39 cascades from the IceCube ‘high-energy starting events’ sample and the other with 16 high-energy ‘track events’. The angular separation between the arrival directions of neutrinos and UHECRs is scanned over. The same events are also used in a separate search using a maximum likelihood approach, after the neutrino arrival directions are stacked. To estimate the significance we assume UHECR magnetic deflections to be inversely proportional to their energy, with values 3◦, 6◦ and 9◦ at 100 EeV to allow for the uncertainties on the magnetic field strength and UHECR charge. A similar analysis is performed on stacked UHECR arrival directions and the IceCube sample of through-going muon track events which were optimized for neutrino point- source searches.
Ključne besede: ultra-high energy cosmic rays, Pierre Auger Observatory, Telescope Array, high-energy neutrinos, IceCube, correlation search
Objavljeno v RUNG: 08.03.2016; Ogledov: 6071; Prenosov: 197
Celotno besedilo (1,11 MB)

Opis: The findings so far of the Pierre Auger Observatory and those of the Telescope Array define some requirements for a possible next generation global cosmic ray observatory: it needs to be considerably increased in size, it needs enhanced sensitivity to composition, and it has to cover the full sky. At the Pierre Auger Observatory, AugerNext aims to conduct some innovative initial research studies on a design of a sophisticated hybrid detector fulfilling these demands. Within a European supported ASPERA/APPEC (Astroparticle Physics European Consortium) project for the years 2011-2014, such R&D studies primarily focused on the following areas: i) consolidation of the detection of cosmic rays using MHz radio antennas; ii) proof- of-principle of cosmic ray microwave detection; iii) test of the large-scale application of new generation photo sensors; iv) generalization of data communication techniques; and v) development of new schemes for muon detection with surface arrays. The AugerNext Consortium consists of 14 principal investigators from 9 countries. This contribution summarizes some achievements of the R&D studies within the AugerNext project.
Ključne besede: ultra-high energy cosmic-ray experiments, Pierre Auger Observatory, Telescope Array, AugerNext research and development study
Objavljeno v RUNG: 03.03.2016; Ogledov: 6885; Prenosov: 200
Celotno besedilo (594,23 KB)

Opis: The quality of the physics results, derived from the analysis of the data collected at the Pierre Auger Observatory depends heavily on the calibration and monitoring of the components of the detectors. It is crucial to maintain a database containing complete information on the absolute calibration of all photomultipliers and their time evolution. The low rate of the physics events implies that the analysis will have to be made over a long period of operation. This requirement imposes a very organized and reliable data storage and data management strategy, in order to guarantee correct data preservation and high data quality. The Fluorescence Detector (FD) consists of 27 telescopes with about 12,000 phototubes which have to be calibrated periodically. A special absolute calibration system is used. It is based on a calibrated light source with a diffusive screen, uniformly illuminating photomultipliers of the camera. This absolute calibration is performed every few years, as its use is not compatible with the operation of the detector. To monitor the stability and the time behavior, another light source system operates every night of data taking. This relative calibration procedure yields more than 2×10[sup]4 raw files each year, about 1 TByte/year. In this paper we describe a new web-interfaced database architecture to manage, store, produce and analyse FD calibration data. It contains the configuration and operating parameters of the detectors at each instant and other relevant functional parameters that are needed for the analysis or to monitor possible instabilities, used for the early discovery of malfunctioning components. Based on over 10 years of operation, we present results on the long term performance of FD and its dependence on environmental variables. We also report on a check of the absolute calibration values by analysing the signals left by stars traversing the FD field of view.
Ključne besede: Pierre Auger Observatory, Fluorescence Detector, detector calibration and monitoring, automated calibration procedure
Objavljeno v RUNG: 03.03.2016; Ogledov: 5551; Prenosov: 213
Celotno besedilo (1,06 MB)

Opis: At the Auger Engineering Radio Array (AERA) of the Pierre Auger Observatory, we have developed a new method to measure the total amount of energy that is transferred from the primary cosmic ray into radio emission. We find that this radiation energy is an estimator of the cosmic ray energy. It scales quadratically with the cosmic ray energy, as expected for coherent emission. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicular to the geomagnetic field at the Auger site, in the frequency band of the detector from 30 to 80 MHz. These observations are compared to the data of the surface detector of the Observatory, which provide well-calibrated energies and arrival directions of the cosmic rays. We find energy resolutions of the radio reconstruction of 22% for the complete data set, and 17% for a high-quality subset containing only events with at least five stations with signal.
Ključne besede: Pierre Auger Observatory, the Auger Engineering Radio Array (AERA), extensive air showers, radio reconstruction: energy resolution
Objavljeno v RUNG: 03.03.2016; Ogledov: 5856; Prenosov: 214
Celotno besedilo (574,66 KB)