exotic nuclei structure and reaction noyaux exotiques ... - IPN - IN2P3

The northern site of the Pierre Auger Observatory
IPNO Participation: O. Deligny , P. Ghia, A. Lemière, I. Lhenry-Yvon, H. Lyberis, T. Suomiärvi
Collaboration : Pierre Auger Collaboration
Le site Nord de l’Observatoire Pierre Auger La construction du site sud de l’Observatoire Pierre Auger a
été terminée en juin 2008. Les données collectées depuis janvier 2004 ont déjà conduit à des résultats majeurs
sur le spectre en énergie, sur la composition et sur les anisotropies des rayons cosmiques aux plus
hautes énergies. Ces résultats motivent la construction du site nord de l’Observatoire qui couvrira plus de
20000km 2 aux USA dans le Colorado. Nous décrivons ici les caractéristiques de ce nouveau site, ainsi
que les spécificités de ses détecteurs et les performances attendues
The Pierre Auger Observatory studies cosmic rays
with energies exceeding 10 18 eV. The construction
of the Southern observatory in Malargüe, Mendoza,
Argentina, was completed in June 2008.
Data collected since January 2004 have yielded
important information on the energy spectrum, the
primary particle composition, the fluxes of photons
and neutrinos and on the anisotropic distribution of
the arrival directions of the most energetic particles
published (see previous contribution in annual report
and references therein).
The recent results mentioned above represent a
significant scientific breakthrough in the field. The
energy spectrum shows a feature at the highest
energies, which is consistent with the Greisen-
Zatsepin-Kuzmin (GZK) effect predicted 40 years
ago. Moreover, it is now evident that there is a detectable
flux of particles from extragalactic sources
within the GZK sphere. The inhomogeneous distribution
of matter in the local universe imprints its
anisotropy on the arrival directions of cosmic rays
above 60 EeV. The challenge is to collect enough
such arrival directions to identify the individual
sources and study their properties. However, the
effect of sources reaching their maximum energy
cannot yet be distinguished from the GZK effect.
Only above 60 EeV there is anisotropy to exploit
for identifying the sources. The southern site of the
Auger Observatory in Argentina collects only about
25 of the crucial trans-GZK events per year, with
fewer than two per year (on average) that have
their longitudinal profiles measured by the air fluorescence
detector. This low rate is not sufficient to
achieve the objectives of identifying the sources.
Auger North will significantly increase the aperture
with its surface extending to 20,000 km 2 while
taking advantage of the well-proven hybrid technique
of Auger South. The combination of two sites
Auger North and South will provide observations of
the entire sky and offer an unprecedented opportunity
for the detailed study of both the astrophysics
of cosmic ray sources and of particle physics at the
highest energies.
Auger North Site
The Northern site of the Pierre Auger Observatory
is located in South East Colorado, U.S.A. The average
altitude is about 1300 m above sea level.
The landscape is almost flat and offers an exceptionally
large area of more than 20,000 km 2 . An
important feature is the system of county roads,
which are spaced on a rectangular one-mile grid
covering a large fraction of the anticipated deployment
area. Auger North will be built with a combination
of the same basic elements as used in Auger
South: Surface Detector (SD) stations and
Fluorescence Detector (FD) telescopes. 4,000 SD
stations will be deployed on a rectangular pattern
on every second corner of the square mile grid,
alternating in adjacent lines over a total area of
20,000 km 2 with a detector spacing of 2 miles (2.3
km).
Fig 1: Auger North site map. The proposed positions of
the fluorescence buildings are shown together with the
distant laser facilities (DLF). The shaded area around
station S12 contains the infill array.
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