Probing the GZK barrier with UHE tau neutrinos

CYRIL LACHAUD; XAVIER BERTOU; PIERRE BILLOIR; OLIVIER DELIGNY; ANTOINE LETESSIER-SELVON

Assergi, Italy

Congreso; TAUP 2001: Topics in Astroparticle and Underground Physics; 2001

Ultra-high energy neutrinos are expected, either as byproducts of interactions of accelerated charged particles with intermediate mediums (in bottom-up models), or in direct decay of particles from a supermassive object (in top-down models); in the latter case they are (together with the photons) dominant in the incident flux. Neutrinos come essentially from pion decay, and the tauic flavour is rare at the source. A muonic/tauic oscillation with. full mixing would result in an equipartition. Tauic neutrinos interacting in the rock produce penetrating tau leptons, which may decay just after emerging from the earth, and generate an atmospheric shower, detectable by the Auger Observatory if it is nearly horizontal. The sensitivity is maximal around 1 EeV, and much larger than with direct atmospheric neutrino interactions. Auger could put strong constraints on production models, and even be sensitive to the "almost certain" GZK neutrino flux [1].