Ultra high energy cosmic ray neutrinos

Abstract

Neutrinos, produced by the collisions of ultra high energy cosmic rays and the 3 K background radiation, require careful treatment of the evolving cosmic ray spectrum. The resulting neutrino differential energy spectrum is flat up to energies of order 10 19eV, thus most events are expected at this energy. The total ν e-flux should be significantly larger than the proton flux at ∼5 × 10 19eV when the recoil proton is correctly treated in photomeson production and when the Bethe-Heitler process (e +e − pair production) is incorporated. Based upon the observed primary proton spectrum we obtain a lower limit on the neutrino flux of ∼5.2/km 2yr sr implying roughly 0.4 detected upward moving events per year in the present Fly's Eye range of sensitivity.