Name : Daniele Fargion E-mail : daniele.fargion@roma1.infn.it TITLE : Shadows of Neutrino Masses on Highest Energy Cosmic Rays ABSTRACT : The Ultra High Energy (UHE) neutrino scattering onto relic cosmic neutrinos in galactic and local halos offers an unique way to overcome GZK cut-off. The UHE nu secondary of UHE photo-pion decays may escape the GZK cut-off and travel on cosmic distances hitting local light relic neutrinos clustered in dark halos or even spread at relativistic regimes. The Z resonant production and the competitive W^+W^-, ZZ pair production define a characteristic imprint on hadronic consequent UHECR spectra. This imprint keeps memory both of the primary UHE nu spectra as well as of the possible relic neutrino masses values, energy spectra and relic densities. Such an hadronic showering imprint should reflect into new surprising spectra morphology of cosmic rays near and above GZK 10^{19}-10^{22}eV cut-off energies detectable by present AGASA and future Auger experiments.