Extremely High Energy Neutrinos, Neutrino Hot Dark Matter, and the   Highest Energy Cosmic Rays
  Extremely high energy (up to 10**(22) eV) cosmic neutrino beams initiate high energy particle cascades in the background of relic neutrinos from the Big Bang. We perform numerical calculations to show that such cascades could contribute more than 10% to the observed cosmic ray flux above 10**(19) eV if neutrinos have masses in the electron volt range. The required intensity of primary neutrinos could be consistent with astrophysical models for their production if the maximum neutrino energy reaches to 10**(22) eV and the massive neutrino dark matter is locally clustered. Future observations of ultra high energy cosmic rays will lead to an indirect but practical search for neutrino dark matter. 
Shigeru Yoshida (Univ.of Tokyo), Guenter Sigl and Sangjin Lee (Univ.of   Chicago)