On heavy Majorana neutrinos as a source of the highest energy cosmic rays

Cosmic ray events beyond the Greisen-Zatsepin-Kuzmin cutoff represent a great challenge for particle physics and cosmology. We show that the physics of heavy Majorana neutrinos, well defined by their masses, cross sections and lifetimes, could explain the highest energy cosmic rays as a consequence of the galactic annihilation of heavy neutrinos as cold dark matter particles. Galactic nuclei accelerators, colliding neutron stars (black holes) or shocks from the collapsed objects could produce ultra high energy cosmic rays as heavy neutrinos beyond the mass threshold at an arbitrary cosmic distance. We comment and also analyse the DAMA results with regard to heavy neutrinos as galactic halo CDM particles. It seems that cosmic ray events accumulated at Yakutsk, Haverah Park, Fly's Eye, HiRes and AGASA beyond the Greisen-Zatsepin-Kuzmin (GZK) cutoff [1] are definitely established as an observational fact, but also as a theoretical problem. The gyroradius of the particle in the galactic magnetic field and available galactic energy sources are in conflict with these ultra high energy (UHE) events, which suggests its extragalactic origin. However, the GZK absorption length λ γp ≃ 10Mpc cannot be reconciled with protons as extragalactic UHE cosmic rays. From a variety of attempts to solve the problem, we mention only two that we find interesting and plausible: light neutrinos [2] and superheavy particles [3]. A detailed analysis of the Z-burst scenario [4] (interaction of UHE and relic light neutrinos) shows that it is difficult to find an astrophysical 1