1. , A possible origin of ultra-high energy cosmic rays: collisions of two galaxies The main goal of the Pierre Auger Project is a detailed study of the energy spectrum and arrival directions of extremely high energy cosmic rays and at least a partial identification of the mass of the cosmic ray particles. To achieve this goal, a sufficiently large sample of cosmic ray events must be collected as quickly as possible in the energy range above 10 19 eV. These experimental data will probably lead to the solution of the puzzle of the origin of these highest energy cosmic rays.The most important experimental difficulty is due to the fact that the cosmic rays with extreme energies are very rare: above the energy of 10 19 eV only 1 particle falls on 1 km 2 during a year. To overcome this difficulty, two detector arrays with total area of 6000 km 2 will be constructed within the Pierre Auger Project. This will be 60 times larger than the largest detector system existing today. To observe the whole sky, the Auger detectors will be placed at two sites, 3000 km 2 each, located in the Southern and Northen hemispheres : in the province of Mendoza (Argentina) and in the state of Utah (USA). Mexico Auger groups: Centro de Investigacion y de Estudios Avanzados. Universidad Autonoma de Puebla. Universidad Michoacana de San Nicolas de Hidalgo. Universidad Nacional Autonoma de Mexico. Data from AGASA: 100km² x 10 years The Observatory employs on each site 1600 particle detectors, uniformly spaced over 3000 square kilometers to measure cosmic ray air showers and four fluorescence detectors overlooking each array. Hybrid detector : surface array (water Cerenkov tanks) and fluorescence detector Good energy and pointing resolution Improved sensitivity to composition Energy cross calibration Auger in 1 year (existing data) E > 10 EeV 6000 events E > 40 EeV 500 events (100) E > 100 EeV 60 events (9) 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 ? 14 countries: Argentina, Australia, Bolivia, Brazil, France, Germany, Italy, Mexico, Poland, Slovenia, Spain, United Kingdom, United States of America, Vietnam. Por el Grupo de México R. Lopez. Noviembre 2002 The project is named after the eminent French physicist,Pierre Auger, who discovered cosmic ray air showers in 1938. Spokesman Emeritus James Cronin (University of Chicago, USA ) Directors of the Pierre Auger Observatory Spokeperson Alan Watson (University of Leeds, United Kingdom) Co-Spokeperson Hans BlümerForschungs zentrum Karlsruhe In a balloon at an altitude of 5,000 meters, Victor Hess, the father of cosmic ray research, discovered "penetrating radiation" coming from Space. 1912 The most advanced cosmic ray experiment nowadays will be implemented with the Pierre Auger Observatory under construction.. Also on dark nights, sensitive light detectors observe the faint fluorescence created by collisions between air shower particles and other air molecules. International collaboration

2. Nicer than the 20-fold for its more regular zenith angle and for falling inside the array, there seems to be large fluctuations far from the core, as the LDF fit is quite bad. It is however a nice event well above 10 19 eV. First hybrid, FD Los Leones May 24, 2001. First light for Fluorescence Detectors. Three 8” PM Tubes Plastic tank White light diffusing liner De-ionized water Solar panel and electronic box Com antena GPS antena Battery box Surface Detector status: The surface detector stations are 10,000-litre water Cerenkov detectors, each equipped with three 220 mm hemispherical photomultipliers. Each is self- contained, with its own data processing unit, radio transceiver and solar power system. Event triggers indicate the possibility that a large air shower has struck the array. Trigger information is sent by radio to the central data acquisition system, which examines them for interesting events. 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. 40 tanks have been deployed into the field for an Engineering Array (EA). Installation of the electronics and the mounting of PMT’s has been completed. By end of 2002, 150 tanks will be deployed and filled with water. The 40th Engineering Array tank (the last one for the EA) has been deployed in the Pampa Amarilla field, and filled with water Aug 02, 2001. First Shower recorded by the Surface Detector. The central data acquisition system is on the Auger campus, located at the edge of the array in the town of Malargue. The campus also contains the detector assembly building with electronics shops, mechanical shops and a water purification plant. Besides the data acquisition system, the handsome new Auger centre building contains offices for staff and Auger collaborators, and a visitors' centre. Southern site status The fluorescence telescope uses Schmidt optics, which, with their aperture stop and corrector lens, allow greater light collection and reduced coma aberration with a spherical mirror. This aperture is sealed with a window that is also an ultraviolet filter for selecting the nitrogen fluorescence lines. As a result, the camera, mirror and all of the electronics are contained in a clean, controlled environment Detectors have been operated in the Los Leones fluorescence building. The telescope alignment reference points are 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. Mirrors 440 PMTs camera Window and filters 2 bays equipped overlooking the EA SD Fluorescence Detector status: Los Leones: the first 2 fluorescence detectors overlooking the EA SD tank with a view of the Andes Coihueco landmarks implantation First hybrid, SD tank HURON Por el Grupo de México R. Lopez. Noviembre 2002