Ultra high-energy cosmic ray observations (original) (raw)

Ultrahigh-Energy Cosmic Rays: Results and Prospects

Brazilian Journal of Physics, 2013

Observations of cosmic rays have been improved at all energies, both in terms of higher statistics and reduced systematics. As a result, the all particle cosmic ray energy spectrum starts to exhibit more structures than could be seen previously. Most importantly, a second knee in the cosmic ray spectrum-dominated by heavy primaries-is reported just below 10 17 eV. The light component, on the other hand, exhibits an ankle like feature above 10 17 eV and starts to dominate the flux at the ankle. The key question at the highest energies is about the origin of the flux suppression observed at energies above 5 • 10 19 eV. Is this the long awaited GZK-effect or the exhaustion of sources? The key to answering this question is again given by the still largely unknown mass composition at the highest energies. Data from different observatories don't quite agree and common efforts have been started to settle that question. The high level of isotropy observed even at the highest energies starts to challenge a proton dominated composition if extragalactic (EG) magnetic fields are on the order of a few nG or more. We shall discuss the experimental and theoretical progress in the field and the prospects for the next decade.

At the doorway to UHE cosmic ray astronomy - Recent results from the Pierre Auger Observatory

AIP Conference Proceedings, 2009

The Pierre Auger Observatory has been designed to measure the most energetic particles in nature. It is located on a plateau in the Province of Mendoza, Argentina, and covers an area of 3000 km 2. The construction has been completed in June 2008 with more than 1600 water Cherenkov detectors positioned on a 1.5 km hexagonal grid and with 24 large area fluorescence telescopes erected at the perimeter of the array. Data taking has been started in 2004 with only 100 tanks and three telescopes taking data. After briefly sketching the design of the observatory, we shall discuss selected first results covering (i) the energy spectrum of cosmic rays with the observation of a flux suppression starting at the GZK energy-threshold, (ii) upper limits of the photon and neutrino flux, (iii) the chemical composition of cosmic rays, and (iv) studies of anisotropies in the arrival direction of cosmic rays including the observation of directional correlations to nearby AGNs.

Astrophysical origins of ultrahigh energy cosmic rays

Reports on Progress in Physics, 2004

In the first part of this review we discuss the basic observational features at the end of the cosmic ray energy spectrum. We also present there the main characteristics of each of the experiments involved in the detection of these particles. We then briefly discuss the status of the chemical composition and the distribution of arrival directions of cosmic rays. After that, we examine the energy losses during propagation, introducing the Greisen-Zaptsepin-Kuzmin (GZK) cutoff, and discuss the level of confidence with which each experiment have detected particles beyond the GZK energy limit. In the second part of the review, we discuss astrophysical environments able to accelerate particles up to such high energies, including active galactic nuclei, large scale galactic wind termination shocks, relativistic jets and hot-spots of Fanaroff-Riley radiogalaxies, pulsars, magnetars, quasar remnants, starbursts, colliding galaxies, and gamma ray burst fireballs. In the third part of the review we provide a brief summary of scenarios which try to explain the super-GZK events with the help of new physics beyond the standard model. In the last section, we give an overview on neutrino telescopes and existing limits on the energy spectrum and discuss some of the prospects for a new (multi-particle) astronomy. Finally, we outline how extraterrestrial neutrino fluxes can be used to probe new physics beyond the electroweak scale.

Cosmic rays at the highest energies - First data from the pierre auger observatory

International Journal of Modern Physics E, 2007

The southern Pierre Auger Observatory, presently under construction in Malargüe, Argentina, is nearing completion. The instrument is designed to measure extensive airshowers 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.

Ultra High-Energy Cosmic Ray Observations: Status and Prospects

Proceedings of European Physical Society Europhysics Conference on High Energy Physics — PoS(EPS-HEP 2009)

Recent measurements of ultra-high energy cosmic rays and neutrinos are reviewed. With several new large scale observatories nearing completion or becoming fully operational only very recently, a large body of high quality and high statistics data is growing up now. Already these first data have started to open up a new window to the high energy Universe giving us first direct clues about the origin of the most energetic particles with energies of about 10 20 eV as well as about their interactions from extragalactic sources to Earth. Also, for the first time full sky views of high energy neutrinos have become available with neutrino telescopes operating on either Hemisphere. While a "smoking gun" is still missing on galactic sources of cosmic rays, constraining upper limits to neutrino fluxes from various source candidates are reported. Thus, future neutrino telescopes, such as KM3NET in the Mediterranean should aim at volumes significantly larger than one cubic kilometer. Besides seeking the sources of galactic and extragalactic cosmic rays, the new generation of cosmic ray and neutrino observatories touches a wide range of scientific issues and they have already provided important results on tests of fundamental physics.

Ultra-high-energy cosmic ray source statistics in the GZK energy range

Astronomy & Astrophysics, 2013

The Greisen-Zatsepin-Kuzmin (GZK) effect, i.e. the interaction of ultra-high-energy cosmic ray (UHECR) protons and nuclei with the intergalactic photon background, results in a drastic reduction of the number of sources contributing to the observed flux above ∼60 EeV. We study quantitatively the source statistics as a function of energy for a range of models compatible with the current data, varying source composition, injection spectrum, source density, and luminosity distribution. We also explore various realizations of the source distribution. We find that, in typical cases, the brightest source in the sky contributes more than one-fifth of the total flux above 80 EeV and about one-third of the total flux at 100 EeV. We show that typically between two and five sources contribute more than half of the UHECR flux at 100 EeV. With such low source numbers, the isolation of the few brightest sources in the sky may be possible for experiments collecting sufficient statistics at the highest energies, even in the event of relatively large particle deflections.

Experimental Summary: Very High Energy Cosmic Rays and their Interactions

EPJ Web of Conferences, 2013

The XVII International Symposium on Very High Energy Cosmic Ray Interactions, held in August of 2012 in Berlin, was the first one in the history of the Symposium, where a plethora of high precision LHC data with relevance for cosmic ray physics was presented. This report aims at giving a brief summary of those measurements and it discusses their relevance for observations of high energy cosmic rays. Enormous progress has been made also in air shower observations and in direct measurements of cosmic rays, exhibiting many more structure in the cosmic ray energy spectrum than just a simple power law with a knee and an ankle. At the highest energy, the flux suppression may not be dominated by the GZK-effect but by the limiting energy of a nearby source or source population. New projects and application of new technologies promise further advances also in the near future. We shall discuss the experimental and theoretical progress in the field and its prospects for coming years. 2 Accelerator Experiments 2.1 Particle and Energy Flow Data from accelerator experiments have guided the development of hadronic interaction models from the early beginnings. A major step forward has now been taken with EPJ Web of Conferences

Observation of ultra high energy cosmic rays from space: Status and perspectives

Progress of Theoretical and Experimental Physics

The study of ultra high energy cosmic rays (UHECRs) offers unique possibilities to probe the energies currently inaccessible by man-made accelerators. Recent years have shed light on several characteristics of these particles, but-due to their extremely low flux-their origin, nature, and acceleration mechanisms are still unclear. Space-based observations have the potential for an increase in statistics, up to several orders of magnitude, and would be able to cover the whole sky, allowing for a direct comparison of spectra and direction of arrival. A detector with the exposure of a few times that of the Pierre Auger Observatory would be able to clarify the observed differences between the northern and southern skies, confirm the existence of TA hot spot, and measure multipolar anisotropies with high precision. A number of novel technologies-from optics to sensors, front-end and read-out electronics-have been developed over the years to achieve this goal. In this paper we describe the progress and results obtained so far and discuss the perspectives of UHECR physics observation from space.