Connection between relic neutrinos and cosmic rays at approx-gt 1020;eV?

The observation of cosmic-ray events above the Greisen - Kuzmin - Zatsepin (GZK) cutoff of 5x1019 eV challenges orthodox modeling. We discuss a possible solution which uses Standard Model (SM) physics augmented only by approx-lt eV neutrino masses as suggested by solar, atmospheric, and terrestrial neutrino detection and the cosmological preference for a hot dark matter component. In this scheme, cosmic ray neutrinos from distant, highest-energy sources annihilate relatively nearby on the relic-neutrino background to produce 'Z-bursts', highly-collimated, highly-boosted (γZ∼1011) hadronic jets. From the SM and hot Big Bang cosmology, the probability for each neutrino flavor at its resonant energy to annihilate within the halo of our galactic supercluster is likely within an order of magnitude of 1%. The kinematics of the annihilation are completely determined by the neutrino masses and the properties of the Z boson. The burst energy is ER=4 (eV/mν)x1021 eV, and the burst content includes, on average, thirty photons and 2.7 nucleons with super-GZK energies. Several tests of the neutrino annihilation hypothesis are indicated. copyright 1998 American Institute of Physics