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The Pierre Auger Observatory Capturing Messengers from the Extreme Universe A new cosmic ray observatory designed for a high statistics study of the The Highest Energy Cosmic Rays Using Two Large Air Shower Detectors Colorado, USA (in planning) Gregory Snow / University of Nebraska Mendoza, Argentina (construction nearing completion) 1 The Pierre Auger Observatory Auger north is planned in Colorado Auger south is here. Malargue is a small town on the high plains not far from a ski area in the Andes. 2 The Auger Collaboration 67 Institutions, 369 Collaborators Argentina Australia Bolivia* Brazil Czech Republic France Germany Italy Mexico Netherlands Poland Portugal Slovenia Spain United Kingdom USA Vietnam* True International Partnership - by non-binding agreement - No country, region or institution dominates – No country contributes more than 25% to the construction. * associate 3 Primary cosmic ray Development of an extensive air shower in the Earth’s atmosphere Mostly muons, electrons and photons at Earth’s surface 4 How a cosmic-ray air shower is formed and detected Primary cosmic rays (mostly protons or light nuclei) impinge on earth’s atmosphere from outer space “Air shower” of secondary particles formed by collisions with air molecules Grid of particle detectors intercept and sample portion of secondaries 1. Number of secondaries related to energy of primary 2. Relative arrival time reveals incident direction 3. Depth of shower maximum related to primary particle type 5 Event timing and direction determination 6 Detecting Cosmic Ray Air Showers Air shower measurements are made by two techniques Fly’s Eye 1) Surface Arrays 2) Fluorescence Telescopes (Fly’s Eyes) Surface Array 7 8 The Hybrid Design Surface detector array + Air fluorescence detectors A unique and powerful design • Nearly calorimetric energy calibration of the fluorescence detector transferred to the event gathering power of the surface array. • A complementary set of mass sensitive shower parameters. • Different measurement techniques force understanding of systematic uncertainties • Determination of the angular and core position resolutions 9 The Surface Array Detector Station Communications antenna Electronics enclosure GPS antenna Solar panels Battery box 3 – nine inch photomultiplier tubes Plastic tank with 12 tons of water 10 The Fluorescence Detector 11 square meter segmented mirror 440 pixel camera Aperture stop and optical filter FD telescopes in closed environment Corrector lens minimizes spherical aberrations, filter brackets 350 nm 11 fluorescence light Installation nearly complete As of October 20, 2007, 1500 of 1600 SD stations 12 Aerial Photos of Fluorescence Buildings November 2006 13 Event seen by all 4 fluorescence detectors and many surface detectors 20 May 2007 E ~ 1019 eV 14 Major result from the Observatory will be featured in the November 9 issue of Science (cover story) Super-galactic plane Galactic coordinates “Correlation of the highest energy cosmic rays with nearby extragalactic objects” 15 Some details • AGN locations from “V-C” (Véron-Cetty and Véron) catalog, D < 75 Mpc • Data set 1 Jan. 2004 – 26 May 2006: 12 events among 15 with E > 56 EeV, Zenith angle < 60o correlate with AGN positions within 3.1o 3.2 expected by chance if flux were isotropic • Data set 27 May 2006 – 31 Aug. 2007: 8 among 13 events correlate, 2.7 expected from isotropic flux • Probability to happen by chance 1.7 10-3 • Two events within 3o of Centaurus A, one of the closest AGNs 16 17 Centaurus A, D=3.4 Mpc 2 UHECRs correlated. Infrared X-ray radio+optical images 18