Ultra High Energy Cosmic Rays: The disappointing model
  We develop a model for explaining the data of Pierre Auger Observatory
(Auger) for Ultra High Energy Cosmic Rays (UHECR), in particular, the mass
composition being steadily heavier with increasing energy from 3 EeV to 35 EeV.
The model is based on the proton-dominated composition in the energy range (1 -
3) EeV observed in both Auger and HiRes experiments. Assuming extragalactic
origin of this component, we argue that it must disappear at higher energies
due to a low maximum energy of acceleration, E_p^{\max} \sim (4 - 10) EeV.
Under an assumption of rigidity acceleration mechanism, the maximum
acceleration energy for a nucleus with the charge number Z is ZE_p^{\max}, and
the highest energy in the spectrum, reached by Iron, does not exceed (100 -
200) EeV. The growth of atomic weight with energy, observed in Auger, is
provided by the rigidity mechanism of acceleration, since at each energy
E=ZE_p^{\max} the contribution of nuclei with Z' < Z vanishes. The described
model has disappointing consequences for future observations in UHECR: Since
average energies per nucleon for all nuclei are less than (2 - 4) EeV, (i) pion
photo-production on CMB photons in extragalactic space is absent; (ii) GZK
cutoff in the spectrum does not exist; (iii) cosmogenic neutrinos produced on
CMBR are absent; (iv) fluxes of cosmogenic neutrinos produced on infrared -
optical background radiation are too low for registration by existing detectors
and projects. Due to nuclei deflection in galactic magnetic fields, the
correlation with nearby sources is absent even at highest energies.
