Angular Correlation Estimates for Ultrahigh Energy Cosmic Rays

Anisotropy in arrival directions of ultrahigh energy cosmic rays offers the most direct way to search for the sources of these particles. We present estimates of the angular correlation in the HiRes sample of stereo events above 10 EeV, and in the combined sample of HiRes and AGASA events above 40 EeV.Comment: 5 pages, 2 figures; to appear in the proceedings of DPF 2004, Riverside, 26 - 31 Aug. 2004 (Int.J.Mod.Phys.A

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the High Resolution Fly's Eye experiment

Journal ArticleWe have measured the cosmic ray spectrum above 1017.2 eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode.We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors.We fit the spectrum to a model consisting of galactic and extragalactic sources

Measurement of the flux of ultra high energy cosmic rays by the stereo technique

ManuscriptThe High Resolution Fly's Eye (HiRes) experiment has measured the flux of ultrahigh energy cosmic rays using the stereoscopic air fluorescence technique. The HiRes experiment consists of two detectors that observe cosmic ray showers via the fluorescence light they emit. HiRes data can be analyzed in monocular mode, where each detector is treated separately, or in stereoscopic mode where they are considered together. Using the monocular mode the HiRes collaboration measured the cosmic ray spectrum and made the first observation of the Greisen-Zatsepin-Kuzmin cutoff. In this paper we present the cosmic ray spectrum measured by the stereoscopic technique. Good agreement is found with the monocular spectrum in all details

First observation of the Greisen-Zatsepin-Kuzmin suppression

Journal ArticleThe High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10^19 eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10^18 eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described

Search for correlations between HiRes stereo events and active galactic nuclei

ManuscriptWe have searched for correlations between the pointing directions of ultrahigh energy cosmic rays observed by the High Resolution Fly's Eye experiment and Active Galactic Nuclei (AGN) visible from its northern hemisphere location. No correlations, other than random correlations, have been found.We report our results using search parameters prescribed by the Pierre Auger collaboration. Using these parameters, the Auger collaboration concludes that a positive correlation exists for sources visible to their southern hemisphere location. We also describe results using two methods for determining the chance probability of correlations: one in which a hypothesis is formed from scanning one half of the data and tested on the second half, and another which involves a scan over the entire data set. The most significant correlation found occurred with a chance probability of 24%

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the high resolution fly's eye experiment

Journal ArticleWe have measured the cosmic ray spectrum above 10^172 eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode.We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors.We fit the spectrum to a model consisting of galactic and extragalactic sources

The Performance of CRTNT Fluorescence Light Detector for Sub-EeV Cosmic Ray Observation

Cosmic Ray Tau Neutrino Telescopes (CRTNT) using for sub-EeV cosmic ray measurement is discussed. Performances of a stereoscope configuration with a tower of those telescopes plus two side-triggers are studied. This is done by using a detailed detector simulation driven by Corsika. Detector aperture as a function of shower energy above 10^17 eV is calculated. Event rate of about 20k per year for the second knee measurement is estimated. Event rate for cross calibration with detectors working on higher energy range is also estimated. Different configurations of the detectors are tried for optimization.Comment: 5 pages, 4 figures, submitted to HEP & N

Cosmic Rays at the Highest Energies -- First Data from the Pierre Auger Observatory --

The southern Pierre Auger Observatory, presently under construction in Malarg"ue, Argentina, is nearing completion. The instrument is designed to measure extensive air-showers with energies ranging from $10^{18}$-$10^{20}$ eV and beyond. It combines two complementary observation techniques; the detection of particles at ground and the coincident observation of associated fluorescence light generated in the atmosphere above the ground. This is being realized by employing an array of 1600 water Cherenkov detectors, distributed over an area of 3000 km$^{2}$, and operating 24 wide-angle Schmidt telescopes, positioned at four sites at the border of the ground array. The Observatory will reach its full size only in 2007 but data are routinely recorded already and have started to provide relevant science results. This talk will focus on the detector characterizations and presents first results on the arrival direction of extremely-high energy cosmic rays, their energy spectrum, and on the upper limit of the photon fraction.Comment: Invited paper presented at the International Symposium on Heavy Ion Physics 2006 (ISHIP 2006), Heavy Ion Physics - Gateway to the Unknown: Complex Structures in Elementary Matter, April 3-6, 2006 Frankfurt am Main, Germany; 13 pages, 7 figure