Can gamma ray bursts produce the observed cosmic rays above 10(20) eV?

It has been suggested that cosmological gamma-ray bursts (GRBs) can produce the observed flux and spectrum of cosmic rays at the highest energies. How ever, recent observations indicate that the redshift distribution of GRBs m ost likely follows that of the star formation rate in the universe, a rate which was much higher at redshifts 1.5-2 than it is today. Thus, most GRBs are at high redshifts. As a consequence, any cosmic rays emitted by these G RBs at energies above similar to 2-3 x 10(19) eV would be strongly attenuat ed by interactions with the 3 K background radiation. If one assumes rough equality between the energy released by GRBs in 10(-2) to 1 MeV photons, an d that released in 10(20) eV cosmic rays, then less than 10% of the cosmic rays observed above 10(20) eV can be accounted for by GRBs. (C) 2000 Elsevi er Science B.V. All rights reserved.