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Title: Strange fireball as an explanation of the muon excess in Auger data
Author: Luis A. Anchordoqui, Haim Goldberg, Thomas J. Weiler

We argue that ultrahigh energy cosmic ray collisions in the Earth atmosphere can probe the strange quark density of the nucleon. These collisions have center-of-mass energies \agt 10^{4.6} A GeV, where A \geq 14 is the nuclear baryon number. We hypothesize the formation of a deconfined thermal fireball which undergoes a sudden hadronization. At production the fireball has a very high matter density and consists of gluons and two flavors of light quarks (u,d). Because the fireball is formed in the baryon-rich projectile fragmentation region, the high baryochemical potential damps the production of u \bar u and d \bar d pairs, resulting in gluon fragmentation mainly into s \bar s. The strange quarks then become much more abundant and upon hadronization the relative density of strange hadrons is significantly enhanced over that resulting from a hadron gas. Assuming the momentum distribution functions can be approximated by Fermi-Dirac and Bose-Einstein statistics, we estimate a kaon-to-pion ratio of about 3 and expect a similar ratio for baryons and pions. We show that, if this were the case, the excess of strange hadrons would suppress the fraction of energy which is transferred to decaying \pi^0's by about 20%, yielding a \sim 40% enhancement of the muon content in atmospheric cascades, in agreement with recent data reported by the Pierre Auger Collaboration.

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Title: Results from the Pierre Auger Observatory
Authors: R. Conceição, for the Pierre Auger Collaboration

The Pierre Auger Observatory is currently the largest observatory of Ultra High Energy Cosmic Rays. Having more data collected than any previous experiment and using a hybrid technique, it can provide important information to unveil the origin and composition of Ultra High Energy Cosmic Rays. Here, we report some results of the Pierre Auger Observatory, namely on the energy spectrum, average depth of the shower maximum and its fluctuations (both sensitive to primary mass composition) and number of muons at ground.

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Some people enjoy living life at the edge, such as participants in extreme sports. At the other extreme are those who relish watching rare events.
Among the latter are astronomers at the Pierre Auger Observatory, a multi-national collaboration to detect the 'light-signature' given off as these cosmic rays hit particles in our atmosphere.
Based in Argentina, the observatory monitors ultra-high energy cosmic rays -  spectacular examples of some of nature's most powerful forces. These rays consist of protons or atomic nuclei travelling near the speed of light from 300 light-years away (over one thousand trillion miles or 1 with 15 zeroes after it). In comparison, our closest star, Alpha Centauri, is only 4.37 light years away.

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The Pierre Auger Project
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In South-eastern Colorado, a land better known for crops and livestock may soon host the world's largest astrophysical detector.

If an international consortium of scientists gets a green light from funding agencies, it will build an array of tanks of purified water - which make passing cosmic rays visible to sensors - across an area of Colorado nearly as large as the state of New Jersey.
The tanks are only 12 feet in diameter, but the network of 4400 of them placed 1.4 miles apart will cover 20,000 square kilometres. The result will be a massive "net" for catching the detritus of some of the highest-energy particles in the universe.

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Scientists launch vast observatory to solve cosmic mysteries
Scientists in western Argentina were set to inaugurate on Friday the world's largest astronomical observatory, hoping to unlock the mysteries of high energy cosmic rays that bombard the Earth.


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Scientists inaugurate worlds largest cosmic-ray observatory
Scientists of the Pierre Auger Observatory, a project to study the highest-energy cosmic rays, will celebrate the inauguration of their 3000-square-kilometer detector array at the southern site of the observatory in Malargüe, Argentina, this Friday, November 14, 2008. The event will mark the completion of the first phase of the observatory construction and the beginning of the projects second phase, which includes plans for a northern hemisphere site in Colorado, USA, and enhancements to the southern hemisphere site.

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This is the assembly building of the Southern array of the Pierre Auger Observatory. In this building, surface detector stations are prepared in advance of their deployment in the field. This international project aims to resolve the mystery of the origin of the highest energy particles in the Universe, which are so rare that to study them with sufficient statistical precision, detectors need to be deployed over a 3000km² area.

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Title: The Fluorescence Detector of the Pierre Auger Observatory - A Calorimeter for UHECR
Authors: B. Keilhauer (for the Pierre Auger Collaboration)

The Pierre Auger Observatory is a hybrid detector for ultrahigh energy cosmic rays (UHECR) with energies above 10^18.5 eV. Currently the first part of the Observatory nears completion in the southern hemisphere in Argentina. One detection technique uses over 1600 water Cherenkov tanks at ground where samples of secondary particles of extensive air showers (EAS) are detected. The second technique is a calorimetric measurement of the energy deposited by EAS in the atmosphere. Charged secondary particles of EAS lose part of their energy in the atmosphere via ionisation. The deposited energy is converted into excitation of molecules of the air and afterwards partly emitted as fluorescence light mainly from nitrogen in the wavelength region between 300 and 400 nm. This light is observed with 24 fluorescence telescopes in 4 stations placed at the boundary of the surface array. This setup provides a combined measurement of the longitudinal shower development and the lateral particle distribution at ground of the same event. Details on the fluorescence technique and the necessary atmospheric monitoring will be presented, as well as first physics results on UHECR.

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Title: Enhancing the Pierre Auger Observatory to the 10^{17} to 10^{18.5} eV Range: Capabilities of an Infill Surface Array
Authors: M.C. Medina, M. Gomez Berisso, I. Allekotte, A. Etchegoyen, G. Medina Tanco, A.D. Supanitsky

The Pierre Auger Observatory has been designed to study the highest-energy cosmic rays in nature (E > 10^18.5 eV). The determination of their arrival direction, energy and composition is performed by the analysis of the atmospheric showers they produce. The Auger Surface Array will consist of 1600 water Cerenkov detectors placed in an equilateral triangular grid of 1.5 km spacing. The aim of this paper is to show that the addition of a "small" area of surface detectors at half or less the above mentioned spacing would allow a dramatic increase of the physical scope of this Observatory, reaching lower energies at which the transition from galactic to extragalactic sources is expected.

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The Pierre Auger Cosmic Ray Observatory will formally welcome Portugal’s Laboratory of Instrumentation and Experimental Particle Physics as its newest member institution during the collaboration meetings 15-19 March in Malarguë, Argentina, site of the world’s largest cosmic ray detector array.

The observatory’s international membership grows to 17 countries with the addition of the Laboratory of Instrumentation and Experimental Particle Physics (LIP). The Portuguese technical and scientific association was created in 1986 with sponsorship by the National Foundation for Science (FCT), the Bureau for International Relations for Science and High Education (GRICES), both under the Portuguese Ministry of Science and Higher Education.

On the vast plain known as the Pampa Amarilla (yellow prairie) in western Argentina, a new window on the universe is taking shape. There, the Pierre Auger Cosmic Ray Observatory is studying the universe's highest energy particles, which shower down on Earth in the form of cosmic rays. While cosmic rays with low to moderate energies are well understood, those with extremely high energies remain mysterious. By detecting and studying these rare particles, the Auger Observatory is tackling the enigmas of their origin and existence.

The first physics results from the observatory, presented in August 2005, include a new cosmic ray spectrum at the highest energies; the results of anisotropy and point source searches; and new limits on the photon content of the primaries; all of which could address several issues within exotic theories of cosmic ray origin.

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Title: Recent results from the Pierre Auger Observatory
Authors: Andreas Zech (for the Pierre Auger Collaboration)

The goal of the Pierre Auger Observatory is to determine the still unknown nature and origin of ultra-high energy cosmic rays. The study of these elusive particles probes astrophysical sites of particle acceleration as well as fundamental interactions at energies unattainable in accelerator facilities. Auger combines two observational techniques, a large surface array and air fluorescence detectors, to observe the extended air showers generated in the atmosphere by cosmic rays.
This hybrid observation yields an excellent resolution and allows for important cross-checks. The Auger South site, located in Mendoza (Argentina), is now nearing completion, with 60% of its surface array and three out of its four fluorescence detectors in operation. First results on the energy spectrum measurement, the search for anisotropies in arrival directions and the upper limit on the photon fraction are discussed.

results from anisotropy searches in the direction of the Galactic Centre(cross).

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