Last Update: October 2000

The AUGER project

1. Goal of the experiment.

The Pierre Auger Observatory is an international scientific project with the objective of studying the highest energy cosmic rays.

Cosmic rays of energy of the order of 10^20 eV have been observed. The origin and accelerating process of these particles is still unknown. Their rate is extremely low. One expects approximately one cosmic ray arriving on an area of one km^2 per century.

In order to collect a significant statistics, the Pierre Auger Observatory covers an area of 3000 km^2. The cosmic rays properties are measured by two independent detector systems. The Surface Detector is a giant array of 1600 water Cherenkov tanks, placed over the area with 1.5 km spacing.

The Fluorescence Detector is a telescope system which reconstructs the cosmic ray shower from the fluorescence light emitted by the atmospheric nitrogen excited by the particles of the cosmic ray shower.

Surface arrays measure the lateral distribution of particles in air showers when theystrike the ground. Fluorescence detectors view the longitudinal development of showers as they move downward through the atmosphere. These two complementary techniques form a uniquely powerful instrument to study the nature of extreme energy cosmic rays.

The Southern Obsevatory will be built in Malargue (Argentina). It is expected to measure the arrival direction, the energy and mass composition of primary cosmic rays collecting about 60 events per year with energy above 10^20 eV and 6000 events per year above 10^19 eV.

An "Engineering Array" with 40 tanks and two fluorescence detector telescopes will be installed at the beginning of the year 2001. It will gradually expand into the full Observatory.

The basic motivations for the AUGER Observatory can be listed as follows:

1. Protons in the cosmic radiation exist with energies above 10^20 eV. The most energetic observed until now has an energy of 3x10^20 eV (50 joules). More than 20 events with energy above 10^20 eV have been already observed.
2. There is no understanding how known astrophysical objects can accelerate protons to energies above 10^20 eV.
3. There is mounting evidence that some of these protons come from point sources.
4. Because of interaction with the 2.7 K cosmic background radiation the sources must be close on a cosmological scale (distance less than 50 Mpc or 150 million light years).
5. These protons are little affected by the magnetic field of our galaxy or the extra-galactic magnetic field. Their arrival direction should point to their source giving a new form of astronomy.
6. The prospect for the discovery of new physics or astrophysics is likely.

The AUGER project is a large international effort.

At present the following countries participate to the project: Argentina, Australia, Bolivia, Brazil, China, Czech Republic, France, Germany, Greece, Italy, Mexico, Poland, Slovenia, United Kingdom and United States.

In Italy groups from the following Universities and Sezioni INFN participate to the project: Catania, Milano, Napoli, Pavia, Roma II and Torino.

2. Achievements during the year 2000.

The design of both the surface detector and the fluorescence detector is being finalized.

The first infrastructure on the site are being built and are almost ready. This includes the Central Building and the building on the small hill "Los Leones" which will house the first 6 fluorescence telescopes.

The construction of the detectors for the Engineering Array is almost completed.

The Engineering Array is made of 40 water Cherenkov tanks and 2 fluorescence telescopes. The installation of the first tanks has started. The telescopes will be installed at the very beginning of year 2001. The Engineering Array should become operational in April 2001.

The INFN groups contribute to the fluorescence detectors of the Engineering Array

by providing the following equipment.

- one complete mirror system
- the UV trasmitting filters for both telescopes
- the camera with light concentrators for both telescopes
- all PMTs with head electronics
- the front-end analog boards

3. INFN contribution in terms of manpower and financial support.

- Manpower: 40 physicists (24 FTE), 9 technicians (3 FTE) and the support from the mechanics and electronics workshops of the Sezioni INFN which are involved in the project.
- Financial support in the year 2000: 735 Mlit for equipment and 205 Mlit for travel expenses.

4. Number of publications: 4

5. Number of talks to Conferences: 8

6. Number of undergraduate and doctoral thesis.

- n. 1 PhD
- n. 9 Laurea degree

7. Leadership role in the experiment.

- D. Camin: task leader of the fluorescence detector electronics
- R. Cester: member Committee referees of the MOUs
- G. Matthiae: member of the AUGER Advisory Group
- P. Privitera: task leader fluorescence detector camera

8. Innovative instruments.

- Current monitor with optoelectronic device to measure the anode current of the PMTs which are run with grounded photocathode (D.Camin, Milano)
- Camera Tracer — an event simulator made of a 440 LED matrix controlled by computer to test the camera of the FD (G.Salina, Roma II).

9. Competing experiments.

It is fair to say that there are at present no competing experiments. Present surface arrays and fluorescence telescope systems have acceptance one or two orders of magnitude less than the Auger Observatory.

Competition may arise in the future from experiments with fluorescence telescopes on satellites (Airwatch).

10. International Committe which has reviewd the experiment

The Auger project is a wide international effort. It has been reviewed by several national Committees in all participating Countries (for example by Sagenap in USA).

In addition every few months the Auger management organizes a "Critical Design Review" with participation of distinguished physicists to critically review the progress of the project on its different aspects.