Astrophysical and Cosmological Production of tau neutrinos

The intrinsic tau neutrino flux produced in high energy cosmological and astrophysical sources has usually been considered negligible in comparison to the electron and muon neutrino fluxes. Also, the cascade tau neutrinos produced by the collisions of primary electron and muon neutrinos with the relic cosmic neutrino background is orders of magnitude less than the primary electron and muon neutrinos flux. Therefore, it is currently expected that any detected tau neutrino component from a source outside the Solar System to be indicative of neutrino oscillation. Our calculations show, however, that a tau neutrino flux component might be produced due to hadronic decays at the source. This tau neutrino component can considerably modify the expected intrinsic tau neutrino spectrum in many astrophysical and cosmological high energy neutrino production scenarios. As a consequence, the observation of a significant tau to muon neutrino ratio at a given energy in high energy neutrino telescopes and detectors may be due to hadronic decays at source and not muon to tau neutrino oscillation in transit.