Department of Physics
University of Roma Tor Vergata
Sezione INFN of Roma Tor
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 1020 eV have been
The origin and accelerating process of these particles are still
Their rate is extremely low: one expects approximately one cosmic ray
arriving on one km2 per century.
In order to collect a significant statistics,
the Pierre Auger Observatory covers an area of 3000 km2. The
cosmic rays properties are measured by two independent detector
systems, the Surface Detector (SD) and the Fluorescence Detector
(FD). The combination of these two complementary techniques
forms a powerful hybrid system.
The Surface Detector is a giant array of 1600 water Cherenkov tanks,
placed over the area with a 1.5 km spacing.
The Fluorescence Detector is a telescope system which
the cosmic ray shower from the fluorescence light emitted by the
atmospheric nitrogen excited by the particles of the cosmic ray shower.
The surface array measures the lateral distribution of particles in air
showers when they strike the ground. The fluorescence detector
longitudinal development of the showers as they move downward through
The Auger Observatory is being built in the Pampa Amarilla, near the
small town of Malargue in the province of Mendoza (Argentina).
The very large acceptance of the Observatory allows studying high
energy cosmic rays with unprecedented statistics. The full
Observatory will collect about 5000 events per year with energy
above 1019 eV. The basic properties of the primary cosmic rays as energy, arrival
direction, and mass composition will be accurately studied.
Motivations for the Pierre Auger Observatories
Protons in the cosmic radiation exist with energies > 1020
eV. The most energetic observed until now has a kinetic energy of 3x1020
eV (50 joules).
There is no understanding how known astrophysical objects can
accelerate protons to energies >1020 eV.
There are hints that some of these protons come from
Because of interaction with the 2.7 K cosmic background radiation
the sources must be close on a cosmological scale (< 50 Mpc or 150
million light years).
The most energetic primary particles should be little affected by
the magnetic field of our
galaxy or by the extra-galactic magnetic field. Therefore their arrival
should point to the source opening a window on a new form of astronomy.
The prospect for the discovery of new physics or astrophysics is
The Italian Agency financing the project is the Istituto Nazionale
di Fisica Nucleare (INFN).
Groups from the following Italian Universities and Sezioni INFN
participate in the Auger Project:
L'Aquila / LNGS
Roma Tor Vergata
The members of the Roma group have the following responsibilities in
the Auger experiment.
Giorgio Matthiae is the current Spokesperson of
He is "Country representative" of Italy in the Auger collaboration and
"Rappresentante Nazionale" dei gruppi Italiani nell'INFN.
Paolo Privitera is
Physics Analysis Tasks.
Valerio Verzi is Convener
of the Analysis Task on "Shower