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GEOGRAPHIC LOCATIONOF THE PIERRE AUGER

OBSERVATORY

Northern Hemisphere:Millard County, Utah

Southern Hemisphere:Malargüe

Mendoza ProvinceArgentina

Malargüe

The Engineering ArrayLocations of the first 40 surface

detector tanks

The first 40 surface detectors

Malargüe, Argentina

• Cosmic rays are particles which travel through outer space and constantly bombard the Earth from all directions.

• The highest-energy cosmic rays are millions of times more energetic than particles produced in the world’s largest particle accelerators.

• The origin of ultra-high energy cosmic rays is unknown.

• High-energy cosmic rays may be indirectly detected at the surface of the Earth by observing showers of particles they produce in the atmosphere.

• The Pierre Auger Observatory will detect and study these air showers in order to resolve the mysteries of ultra-high energy cosmic rays: their nature and their origin.

A possible origin ofultra-high energy cosmic

rays: collisions of twogalaxies

Scientific Aspects of the Pierre Auger Observatory

The Search for the Origin of Ultra-HighEnergy Cosmic Rays

The International Collaboration of the Pierre Auger Observatory

About 250 scientists from more than 30 institutionsand 19 countries participate in the experiment.

Participating Countries:Argentina, Armenia, Australia, Bolivia, Brazil, China, Czech Republic, France, Germany, Greece, Italy, Japan, Mexico, Poland, Russia, Slovenia, United Kingdom, United States, Vietnam

Collaborating Institutions in the United States:• University of California at Los Angeles• University of Chicago• Colorado State University• University of Colorado• The Fermi National Accelerator Laboratory• Louisiana State University• Michigan Technological University• University of Mississippi• University of Nebraska• University of New Mexico• Northeastern University• Pennsylvania State University• University of Utah

Participatingcountries

shown in red.

The project is named after the eminent French physicist, Pierre Auger, who discovered cosmic ray air showers in 1938.

Directors of the Pierre Auger ObservatoryJames Cronin (University of Chicago, USA)

Alan Watson (University de Leeds, United Kingdom)

The Pierre AugerCosmic Ray Observatory

The development of a cosmic rayair shower in the atmosphere

The Detectors

• The Observatory employs 1600 particle detectors uniformly spaced over 3000 square kilometers

to measure cosmic ray air showers. • Also on dark nights, sensitive light detectors observe the faint fluorescence created by collisions between air shower particles and other air molecules.

Surface detector

Fluorescence telescope

Surface Detectors

Antenna fortransmitting data

Solar panel for charging battery

Tank containing12000 liters of pure water

Lightdetectors

Electronic apparatusand battery

Two types of detectors work togetherto measure cosmic ray air showers

Surface detectors

Fluorescencetelescope

Angle

Air showerplane

1.5 kilometers

Primary cosmic ray

Members of the collaboration withthe first Surface Detector tank

installed in the field

Solar panel

An “air shower” of secondaryparticles is created by collisionswith air molecules

A primary cosmic ray (usually a proton or light nucleus) impinges on the earth’s atmosphere from outer space

A grid of particledetectorsintercepts andsamples a portionof the arrivingsecondary particles

• The number of secondaries is related to the primary cosmic ray’s energy• The relative arrival time of secondaries tells the incident direction of the primary cosmic ray

How is a cosmic ray air showerformed and detected?

Cosmic ray air showers were firstobserved by one of the fluorescence

detectors in May 2001!

Computer-reconstructed image:cosmic ray trail in atmosphere “seen” by

multi-channel fluorescence camera