On the Relation of Atmospheric and Cosmogenic Neutrino Fluxes and Cosmic Ray Composition

Atmospheric neutrinos produced by cosmic ray interactions in the atmosphere are the most important source of background in neutrino telescopes such as AMANDA, IceCube, ANTARES or the future KM3NeT. They come for free to serve as calibration reference and precise knowledge of their absolute flux is mandatory in searches for neutrino point sources, for diffuse fluxes or neutrino oscillation studies. Uncertainties at the 1-100 TeV scale are directly related to those of all-particle cosmic ray spectrum as well as to the cosmic ray composition. Cosmogenic neutrinos originating from the propagation of cosmic rays start to be important above energies of 1015eV where they may serve as a probe of the transition from galactic to extragalactic cosmic rays and as a probe of the GZK-effect. Again, the expected fluxes are very sensitive to the cosmic ray composition. This note discusses the present uncertainties of the cosmic ray composition and the level of sensitivity to the atmospheric and cosmogenic neutrino fluxes.