The Pierre Auger Observatory and Neutrinos

The Pierre Auger Observatory is a hybrid detector (fluorescence telescopes and ground array) of cosmic rays of ultra-high energy, designed to observe extensive atmospheric showers. It has also a capability to observe rare neutrino-induced showers: if they are almost horizontal, they can be distinguished from the background produced by the muonic tails of nucleic showers. They may be initiated either by a direct interaction of a neutrino in the atmosphere, or, with a larger probability, by the decay of a tau lepton emerging from the ground after an interaction of a tau neutrino within the earth. An evaluation of the sensitivity of the Surface Detector of Auger to such 'earth-skimming' events is presented, and a procedure to discrimine them from the background is described