Study of a detector array for Upward Tau Air-Showers

The cosmic ray spectrum extends to energies above 10 eV. In direct production or acceleration models, as well as by photo-pion interaction high energy cosmic ray flux must contain neutrinos and photons. The latter are absorbed by cosmic radiations while neutrinos are not. The need of a Neutrino Astronomy is compelling. In this paper a study of a detector array designed to measure horizontal τ air-showers emerging from the ground, produced by ντ interactions with the Earth’s crust, is presented. Each array unit is composed of a pair of scintillator tiles mounted on a frame with a front field of view of about 0.1 sr, optimized to distinguish between up-going and down-going crossing particles by their time of flight. The detector array sensitivity, the size of the array and the τ shower identification are discussed. Because of the almost complete mixing of νμ → ντ the ultrahigh energy neutrino tau and its minimal consequent tau-airshower rate is estimated; assuming that the neutrino energy spectrum follows a Fermi-like power law E, the sensitivity with 3 years of observation is estimated to be about 60 eV cmssr in the energy range 10 eV. This value would provide competitive upper limit with present and future experiments. We found also that, in the same time, this system can observe about one GZK neutrino event per km.