Angela Olinto, University of Chicago
Deciphering the Extreme Universe
The nature and origin of the highest energy particles ever to be observed
are still elusive. They are messengers of an extreme universe which can test
the limits of physical laws. The largest cosmic ray experiments are starting
to probe the extremely high-energy region where pointing to cosmic ray
sources is feasible and a long awaited Greisen-Zatsepin-Kuzmin feature in
the spectrum is expected. Past experiments have claimed opposing results:
AGASA sees an intriguing excess of cosmic rays above 1020 eV that
challenges most theoretical models while HiRes does not confirm the excess.
After reviewing the present state of the experiments and theoretical models
for the highest energy cosmic rays, we will discuss the status of the
newest observatory, the Pierre Auger project and possible outcomes.