Enhanced cosmological GRB rates and implications for cosmogenic neutrinos

Gamma-ray bursts, which are among the most violent events in the universe,are one of the few viable candidates to produce ultrahigh energy cosmic rays.Recently, observations have revealed that GRBs generally originate frommetal-poor galaxies and do not directly trace cosmic star formation, as mighthave been assumed from their association with core-collapse supernovae. Severalimplications follow from these findings. The redshift distribution of observedGRBs is expected to peak at higher redshift (compared to cosmic starformation), which is supported by the mean redshift of the Swift GRB sample,~3. If GRBs are, in fact, the source of the observed UHECR, then cosmic-rayproduction would evolve with redshift in a stronger fashion than has beenpreviously suggested. This necessarily leads, through the GZK process, to anenhancement in the flux of cosmogenic neutrinos, providing a near-term approachfor testing the gamma-ray burst-cosmic ray connection with ongoing and proposedUHE neutrino experiments.Comment: 9 pages, 5 figures, references and two appendices added, conclusions unchanged; accepted for publication in Phys.Rev.