Search for ultra-high energy neutrinos from below and above the horizon with the ANTARES Telescope

Over one century has passed since the discovery of cosmic rays and their origin is still uncertain. The multi-messenger approach seems to be the key in this area of research. Neutrinos are among the best cosmic messengers thanks to the fact they are neutral, stable and weakly interacting. ANTARES is the first undersea Neutrino Telescope, its main purpose is the search for neutrino fluxes from astrophysical objects. It is placed on the bottom of the Mediterranean Sea, ∼ 40 km south-east from the coast of Toulon (France). Its observation is based on the detection of the Cherenkov radiation induced by the passage in water of superluminal charged particles produced by the interaction of cosmic neutrinos near the detector. ANTARES is taking data since 2007, until now we have analyzed the data collected up to 2012. No neutrino signals have been found above the expected background and upper limits on the flux normalization of an Ev-2 energy spectrum have been set. In order to limit the background from down-going atmospheric muons, the analysis strategy focuses on the so-called "up-going" events, which are those that have traversed the Earth. The development of a strategy for the reconstruction and the identification of "downgoing" neutrinos is in progress. By including them in the analysis it will be possible to enlarge the field of view of ANTARES and the accessible energy range up to the EeV.