The Pierre Auger Observatory is presently the largest cosmic-ray detector in the world. It is dedicated to the study of cosmic rays at the highest energies (E > 1019
eV). The Pierre Auger Observatory is an array of water tanks covering 3000 km² in the pampa in Argentina (Mendoza).
The group of IPN Orsay is involved at different levels in the hardware and in the analysis of the data of the observatory.
From the detection of showers to the cosmic-ray spectrum
Building the cosmic-ray spectrum requires different steps: control and selection of relevant signals for the 1600 water tanks, reconstruction of angle and energy of incident cosmic rays, evaluation of the exposure of the array as a function of time.
The search for anisotropies in the arrival directions of cosmic rays is a key tool to understand their origin. At the highest energies, we hope to track back their sources, while around 1018-1019 eV, the very large statistic enables the search for large scale structures in their arrival directions, which could sign a transition from galactic to extragalactic cosmic rays.
WHICH Primary at the HIGHEST energies?
The knowledge of the cosmic-ray primary composition is an other crucial parameter to understand their origin. In particular, we expect that at the highest energies, the lighest cosmic rays, only slightly deviated by magnetic fields, will point to their sources.
For this, we need observables sensitive to the primary composition, such as the muon content of the showers detected with the surface detector.
Radio detection OF COSMIC rays showers
In the framework of the ANR GIGAS, we evaluate the feasibility of a measurement of the electronic cascade of showers with a 100% duty cycle, detecting with optimized antennas the microwave emission induced by the electrons and positrons of such cascades. This measurement would give access, together with the signals of water tanks, to a new observable for composition measurements.
ElectronicS Of the surface detector and upgrade of the Observatory
The Pierre Auger collaboration plans to pursue running the observatory with improved capabilities, particularly for the discrimination of primaries. Different options for muon detectors are under study and will be evaluated very soon. It is also necessary to upgrade the electronics. The IPN Orsay, in charge of the electronics of the surface detector since its entry in the collaboration in 2000, is at the head of this upgrade project.