Can high energy neutrino annihilation on relic neutrinos generate the observed highest energy cosmic-rays?
Abstract
Annihilation of high energy, 1021eV, neutrinos on big bang relic neutrinos of 1eV mass, clustered in the Galactic halo or in a nearby galaxy cluster halo, has been suggested to generate, through hadronic Z decay, high energy nucleons and photons which may account for the detected flux of >1020eV cosmic-rays. We show that the flux of high energy nucleons and photons produced by this process is dominated by annihilation on the uniform, non-clustered, neutrino background, and that the energy generation rate of 1021eV neutrinos required to account for the detected flux of >1020eV particles is >1048 erg/Mpc3 yr. This energy generation rate, comparable to the total luminosity of the universe, is 4 orders of magnitude larger than the rate of production of high energy nucleons required to account for the flux of >1019eV cosmic-rays. Thus, in order for neutrino annihilation to contribute significantly to the detected flux of >1020eV cosmic-rays, the existence of a new class of high-energy neutrino sources, likely unrelated to the sources of >1019eV cosmic-rays, must be invoked.
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