Upper limit on the diffuse flux of UHE tau neutrinos

The Pierre Auger Observatory has been designed to study the cosmic rays of ultra-high energy by observing extensive atmospheric showers. It also has the capability of detecting ultra-high energy neutrinos by searching for very inclined showers with a significant electromagnetic component. The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau-neutrinos ντ that interact in the Earth's crust. For neutrinos in the energy range 2×1017 eV