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The arrival directions of extremely high energy cosmic rays (EHECR) above 4 × 10 19 eV, observed by four surface array experiments in the northern hemisphere, are examined for coincidences from similar directions in the sky. The total number of cosmic rays is 92. A significant number of double coincidences (doublet) and triple coincidences (triplet) are(More)
Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these(More)
In this Letter we examine the arrival directions of the most energetic cosmic rays (E > 2 10 19 eV) detected by several air shower experiments. We find that data taken by different air shower arrays show positive correlations, indicating a non–uniform arrival direction distribution. We also find that the events with energy > 4 10 19 eV exhibit a correlation(More)
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and(More)
We describe a method to analyse inclined air showers produced by ultra high energy cosmic rays using an analytical description of the muon densities. We report the results obtained using data from inclined events (60 • < θ < 80 •) recorded by the Haverah Park shower detector for energies above 10 19 eV. Using mass independent knowledge of the UHECR spectrum(More)
We report on the analysis of air showers observed in coincidence by the Antarctic Muon and Neutrino detector array (AMANDA-B10) and the South Pole Air Shower Experiment (SPASE-1 and SPASE-2). We discuss the use of coincident events for calibration and survey of the deep AMANDA detector as well as the response of AMANDA to muon bundles. This analysis uses(More)
Our knowledge of the mass composition of cosmic rays is deficient at all energies above 10 17 eV. Here, systematic differences between different measurements are discussed and, in particular, it is argued that there is no compelling evidence to support the common assumption that vast majority of the cosmic rays of the highest energies are protons. Our(More)
At the Haverah Park Array a number of air shower observables were measured that are relevant to the determination of the mass composition of cosmic rays. In this paper we discuss measurements of the risetime of signals in large area water-Cherenkov detectors and of the lateral distribution function of the water-Cherenkov signal. The former are used to(More)
The rate of cosmic ray showers at large zenith angles: a step towards the detection of ultra-high energy neutrinos by the Pierre Auger Observatory Abstract It is anticipated that the Pierre Auger Observatory can be used to detect cosmic neutrinos of > 10 19 eV that arrive at very large zenith angles. However showers created by neutrino interactions close to(More)
Air showers recorded by the Haverah Park Array during the years 1974-1987 have been re-analysed. For the original estimate of the energy spectrum, a relationship between the ground parameter ρ(600) and the primary energy, as determined by Hillas in the 1970s, was used. Here we describe the energy spectrum obtained using the QGSJET98 interaction model in the(More)