On Big Bang Relics, the Neutrino Mass and the Cosmic Ray Spectrum
  It is shown that high energy features of the cosmic ray spectrum, in particular the kink around 4 PeV and the corresponding change in spectral index, may be explained from interactions between highly energetic protons and relic Big Bang antineutrinos, if the latter have a rest mass of about 0.4 eV/$c^2$. This explanation is supported by experimental data from extensive air-shower experiments. 
Richard Wigmans