P.Auger, a major step: Need high statistics large detection area : 2 x3000 km² Uniform sky coverage 2 sites located in each hemisphere Argentina and USA Hybrid detector : surface array (water Cerenkov tanks) + fluorescence detector  Good energy and pointing resolution, Improved sensitivity to composition Energy cross calibration The World's Largest Cosmic Ray Detector The Pierre Auger Observatory is designed to detect and study cosmic rays around and above the GZK cutoff, i.e. at energies exceeding eV, with an unprecedented quality and precision. Within our present knowledge, there is no standard explanation to the production and acceleration of any particle in the universe at such macroscopic energies. To solve this astrophysical puzzle of more than 30 years, an international scientific collaboration has designed and is building Auger. Northern hemisphere Millard county Utah, USA Southern hemisphere: Malargüe de Provincia de Mendoza Argentina Collaboration: >250 researchers from 56 institutions and 20 countries: Argentina, Armenia, Australia, Bolivia, Brazil, Chile, China, Czech Republic, France, Germany, Greece, Italy, Japan, Mexico, Poland, Russia, Slovenia, United Kingdom, United States of America, Vietnam US Auger groups: Colorado, Colorado State, Chicago, Fermilab, LSU, Michigan Tech, Mississippi, Nebraska, New Mexico, Northeastern, Penn State, UCLA, Utah The puzzle of UHECR (Ultra High Energy Cosmic Rays) E>10 19 eV, “ particles which do exist... But perhaps shouldn’t!” The puzzle of UHECR (Ultra High Energy Cosmic Rays) E>10 19 eV, “ particles which do exist... But perhaps shouldn’t!” Ludwik M. Celnikier Physics issues with Auger: Where does the spectrum end ? Is there a GZK cutoff? Are the sources local (<150 Mly)? Primary nature (composition) ? Nuclei? Protons ? Gamma rays? Neutrinos? Or...? What is the source of UHECR ? Bottom-Up or Top-Down scenario ? Data from Agasa: 100km² x 10 years On each site: 1600 SD (surface detectors) 4 FD stations (fluorescence detectors) Duty Cycle:Efficiency: SD 100% >90% above 10 EeV FD 10% Energy resolution: SD aloneHybrid mode 100 EeV 15% 10% 10 EeV 30% 20% Angular resolution: SD aloneHybrid mode 100 EeV 0.5°0.20° 10 EeV 1.0° 0.35° Auger in 1 year : (existing data) E > 10 EeV 6000 events E > 40 EeV 500 events (100) E > 100 EeV 60 events (9) 20 months of Auger running: (Cosmologically distributed sources, E -2 spectrum, GZK cut off) Auger sky after 3 years of Auger running: ( E>10 19, 15 sources randomly distributed )

Town of Malargüe Los Leones : the first 2 fluorescence detectors overlooking the EA Central campus and Assembly Hall Building the Engineering Array at the Southern Site Fluorescence Detector status: Auger now has access to the Los Leones fluorescence building. The telescope alignment reference points are being installed. The mirror support systems for both telescopes and one set of mirrors are on site and ready for installation. Data link from Los Leones to Central Campus is now operational. Auger collaborators march in the Malargue 50th Anniversary parade (with flamenco dancers), Nov Official ribbon cutting, Nov Open house for the public Tanks arriving by truck from Brazil Surface Detector status: Water purification plant operational Detector assembly building at Central Site is completed and in use. Data acquisition equipment (CDAS) has been installed and is operating. Brackets for the solar panels and electronics now include the 3 m communications antenna mast (improved previous design). All solar panels and battery boxes have been delivered. 18 tanks have been deployed into the field; 13 are filled with water. Installation of the electronics and the mounting of PMT’s has started By end of March, all 40 EA tanks (38 in field + 2 control) will be deployed and filled with water. 2001: Engineering Array 15 april  38 SD detectors covering 70km² 15 june  2 FD camera (each 30 x30°) 2004: Southern site completed First tank deployed: Priscila, Queen of the Desert SD tank with a view of the Andes Installing electronics boxes Each detector is powered by a solar panel Unloading the tanks The completed FD building will house 6 telescope/ camera arrays View from one of the telescope bays Completing the comms tower Filter window detail The surface detector array is on a flat plane at 1400 m altitude Three 8” PM Tubes Plastic tank White light diffusing liner De-ionized water Solar panel and electronic box Comm antenna GPS antenna Battery box Mirrors 440 PMTs camera Window and filters 2 bays equipped overlooking the EA SD 38 tanks of the Engineering Array The pampa amarilla, 3000 km 2 of grassland