Solving the Mystery of the

Ultra-High Energy Cosmic RaysThe Pierre Auger Observatory

Pablo BauleoPhysics DepartmentColorado State UniversityFort Collins CO 80523

Southern Site: Malargue, Argentina Northern Site: Southeast Colorado, USA

http://www.auger.org.ar

Historical high pointsHistorical high points1912

Victor Hess discovers

“penetrating radiation” from space

1938Pierre Auger discoversExtensive air showers

DAuger varied distance and lead covering

Fast electronic counters

Pb

For energy > 5 * 1019

Greisen, Zatsepin-Kuzmin (GZK) Cut OffParticles > 5 * 1019 eV

must be < ~ few*50 Mpc away

1962: Penzias-Wilson: Cosmic Microwave Background

p + CMB p + 0

n + +

Energy (eV)

Flux

(m

2 sr

s e

V)-1

Highest energy event:3.2 x 1020 eV

Fly’s Eye in Utah in 1991

Today a lot is known about the cosmic ray flux…

The Auger project is focused on the highest energies.

At the high end of the spectrum the energies are macroscopic

Highest energy events are around 2*1020 eV 30 Joules

…dropping my laptop computer from shoulder height

This energy is concentrated in, say, one proton. It corresponds to kinetic energy of…

…a tennis ball at 40 miles per hour

…a person walking slowly, deep in thought.

Flux @ 1020 eV 1 CR/(km2 sr century)

Cosmic MysteriesCosmic MysteriesWhere do Ultra High Energy Where do Ultra High Energy Cosmic Rays Come From?Cosmic Rays Come From?

No convincing acceleration process for explaining particle energy > 1020 eV

A handful of super-GZK events have been reported.

Sources of particles > 1020 eV must be closer than about 50 Mpc because of CMB

No likely acceleration sites have been found nearby.

The highest energy cosmic rays should point back to possible sources

Point sources or uniform on the sky?

The primary cosmic ray initiates a shower. There are two basic detection techniques:

(1) Particles reach ground

(2) Nitrogen fluorescence10% duty factor – dark nights

Up to order 1011 particles

Height ~20 km.a.s.l

Height ~ 1500 m.a.s.l

Extracting information from an EAS• Tank timing

Arrival direction• Number of particles in tanks

Total Energy• Telescope image (digital camera like)

Arrival direction• Light detected

Total EnergyRedundant measurement for cross-checks

Animation of an eventmeasured in Argentina

The Auger Collaboration• 18 Participating Countries - 50 Institutions, >280 ScientistsArgentina MexicoAustralia NetherlandsBolivia* PolandBrazil Slovenia Czech Republic SpainFrance South KoreaGermany United Kingdom Greece USAItaly Vietnam*

• Participating US institutions:

UCLA Michigan TechCase Western MinnesotaChicago NebraskaColorado New MexicoColorado State NortheasternFermilab (and ANL) Penn StateLouisiana State Utah

Auger north is planned in Colorado

Malargue is a small town on the high plains not far from a ski area in the Andes.

Auger south is here.

View of Los LeonesView of Los LeonesFluorescence SiteFluorescence Site

Six Telescopes viewing 30°x30° Six Telescopes viewing 30°x30° eacheach

Schmidt corrector ring

2.

2 m

opt. Filter(MUG-6)

UV optical filter(also: provide protectionfrom outside dust)

Camera with 440 PMTs (Photonis XP 3062)

Schmidt Telescope using 11 m2 mirrors

Atmospheric MonitoringAtmospheric Monitoring

Balloon probes (T,p)-profiles

LIDAR at each FD building

Central laser facility (fiber linked to tank)

light attenuation lengthAerosol concentration

steerable LIDAR facilities located at each FD eye

•• LIDARLIDAR at each eye at each eye•• cloud monitorscloud monitors at each eye at each eye•• central central laserlaser facility facility•• regular regular balloon flightsballoon flights

Aligned Water TanksAligned Water Tanksas seen from Los Leonesas seen from Los Leones

Water Tank in the PampaWater Tank in the Pampa

Solar PanelElectronics enclosure

40 MHz FADC, local triggers, 10 Watts

Communication antenna GPS antenna

Batterybox

Plastic tank with 12 tons of waterthree 9”

PMTs

receiving ~20 tanks/week

Tank Preparation and Assembly

Transportation into fieldWater deployment

installation of electronics

Installation Installation ChainChain

Central campus with visitors center

Assembly building, yard

Coihueco(fully operational)

Loma Amarilla(in preparation)

Los Leones(fully operational)

Los Morados(fully operational)

Proposed Layout in Southeast ColoradoProposed Layout in Southeast Colorado

http://www.auger.org.ar