Session B16 - Neutrino and Gamma Ray Astrophysics.
MIXED session, Saturday morning, April 29
202C, Convention Center
It has been suggested that cosmological \gamma-ray bursts can produce the observed flux of cosmic rays at the highest energies. However, recent observations indicate that the redshift distribution of \gamma-ray bursts most likely follows the redshift distribution of the average star formation rate in the universe, a rate which was much higher at redshifts between 1.5 and 2 than it is today. We show that as a consequence, energy losses suffered by ultrahigh energy cosmic rays caused by meson-producing interactions with photons of the big-bang relic background radiation would have a profound effect on both the flux and energy spectrum of these cosmic rays which would be observed at Earth during the present epoch. The cosmic rays with energies above 10 EeV from \gamma-ray bursts which we predict would have a much lower flux than that observed and would have a sharp cutoff in their spectrum at an energies above \sim 30 EeV, an order of magnitude lower in energy than the highest energy cosmic ray event reported by the Fly's Eye detector array.