1. The Highest Energy Cosmic Rays Two Large Air Shower Detectors
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
I am pleased to report on progress on a new cosmic ray observatory now under construction in Argentina.
The objective of the Pierre Auger Observatory is to make a full sky, high statistics, study of cosmic rays at the highest energies.
The Auger Observatory will consist of sites – one in each hemisphere at mid latitude – so as to have full sky coverage.
The southern site of the Auger Observatory is located in the province of Mendoza, Argentina near the city of Malargüe. The northern site will be in south east Colorado.
I will report on:
Progress in the observatory construction.
The performance of the detectors now in operation.
The quality of the data.
Preliminary results.
Colorado, USA
(in planning)
Mendoza, Argentina
(construction nearing completion)
Gregory Snow / University of Nebraska

2. 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.

3. The Auger Collaboration 67 Institutions, 369 Collaborators
Argentina Netherlands
Australia Poland
Bolivia* Portugal
Brazil Slovenia
Czech Republic Spain
France United Kingdom
Germany USA
Italy Vietnam*
Mexico
* associate
True International Partnership - by non-binding agreement -
No country, region or institution dominates – No country contributes more than 25% to the construction.
The Observatory is being built by an eclectic mix of high energy physicists, low energy physicists, cosmic ray physics and a few astronomers from 63 institutions in 16 countries. The Auger collaboration is unique among large international science projects in that there is no dominant country or institution – indeed a true partnership.

4. Development of an extensive air shower in the Earth’s atmosphere
Primary cosmic ray
Development of an extensive air
shower in the Earth’s
atmosphere
Mostly muons, electrons and photons at Earth’s surface

5. 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
Number of secondaries
related to energy of primary
Relative arrival time
reveals incident direction
3. Depth of shower maximum
related to primary particle
type

6. Event timing and direction determination

7. Detecting Cosmic Ray Air Showers
Air shower measurements are made by two techniques
Surface Arrays
Fluorescence Telescopes (Fly’s Eyes)
Here is a cartoon of a shower with the two methods of detection.
The fluorescence detector – sometimes called a fly’s eye – records the fluorescence light produced in the atmosphere as the shower cascades toward the earth.
The surface detector is an array of particle detectors that records some of the billions of shower particles that hit the earth.
Fly’s Eye
Surface Array

9. 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
Let me focus a bit more on the power of the hybrid design.
Remark on each of the features of the hybrid design. I will illustrate these features of the hybrid design as I go along.

10. The Surface Array Detector Station
GPS antenna
Communications
antenna
Let me describe some of the details of the self-contained surface detector station. It a water cerenkov detector designed to be simple and robust. The Pampa Amarilla is in the foreground and the Andes are in the background. We spent a lot of time out here in the desert and have grown quite fond of it.
Electronics
enclosure
Solar panels
Battery box
3 – nine inch
photomultiplier
tubes
Plastic tank with
12 tons of water

11. The Fluorescence Detector
11 square meter segmented mirror
Here are details of the fluorescence telescopes – the most important feature is the use of Schmidt optics.
The schematic shows features of the fluorescence detector.
The segmented mirror.
440 pixel camera.
That is the use of Schmidt with aperture stop and partial correct ring for reduced spherical aberration. The optical filter that passes the nitrogen fluorescence lines acts as a window to provide a closed and controlled environment.
440 pixel camera
Aperture stop and optical filter
Corrector lens
minimizes spherical
aberrations, filter
brackets 350 nm
fluorescence light
FD telescopes in closed
environment

12. Installation nearly complete
As of October 20, 2007, 1500 of 1600 SD stations

13. Aerial Photos of Fluorescence Buildings November 2006

14. Event seen by all 4 fluorescence detectors and many surface detectors
20 May E ~ 1019 eV

15. 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”

16. Some details
AGN locations from “V-C” (Véron-Cetty and Véron) catalog, D < 75 Mpc
Data set 1 Jan – 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

18. Centaurus A, D=3.4 Mpc
2 UHECRs correlated.
Infrared
X-ray
radio+optical images