High energy neutrinos from GRBs and cosmic rays


Has the GZK Suppression been discovered?

Authors:John Bahcall and Eli Waxman
Journal: Phys. Lett. B, 556/1-2, 1-6, hep-ph/0206217

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Abstract: We show that the combined observational data from the Fly's Eye, HiRes, and Yakutsk cosmic ray experiments strongly suggest (~ 7 sigma) that the Greisen-Zatsepin-Kuzmin (GZK) cutoff is present in the observed energy spectrum of ultra-high-energy cosmic rays. However, Top-Down models which invoke decaying heavy particles are consistent with the AGASA cosmic ray data. High statistics measurements in the cosmic ray energy range between 1018 eV to 5×1019 eV will be necessary to test for the characteristic differences between Top-Down models and more conventional models.

High energy neutrinos from cosmological gamma-ray burst fireballs

Authors: Eli Waxman and John Bahcall
Journal: Physical Review Letters, 78, 2292-2295 (March 24, 1997); astro-ph/9701231.

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Abstract: Observations suggest that gamma-ray bursts are produced by the dissipation of the kinetic energy of a relativistic fireball. We show that a large fraction (more than 10%) of the fireball energy is expected to be converted by photo-meson production to a burst of approximately 1014 eV neutrinos. A km square neutrino detector would observe at least several tens of events per year simultaneously with satellite detected gamma-ray bursts and test for neutrino properties (e. g., flavor oscillations for which upward moving tau's would be a unique signature) with an accuracy many orders of magnitude better than is currently possible.

Ultra-high Energy Cosmic Rays May Come from Clustered Sources

Authors: John Bahcall and Eli Waxman
Journal: The Astrophysical Journal, 542, 542-547 (20 October 2000), hep-ph/9912326.

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Abstract: Clustering of cosmic-ray sources affects the flux observed beyond the cutoff imposed by the cosmic microwave background and may be important in interpreting the AGASA, Fly's Eye, and HiRes data. The standard deviation, , in the predicted number, N, of events above 1020 eV is /N = 0.9(r0/10 Mpc)0.9, where r0 is the unknown scale length of the correlation function (r0~= 10 Mpc for field galaxies, H0 = 50 km s-1 Mpc-1). Future experiments will allow the determination of r0 through the detection of anisotropies in arrival directions of ~ 1020 eV cosmic-rays over angular scales of ~ r0/30 Mpc.

High Energy Neutrinos from Astrophysical Sources: An Upper Bound

Authors: Eli Waxman and John Bahcall
Journal: Physical Review D, 59, 023002 (1 February 1999); hep-ph/9807282.

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Abstract: Gamma-ray bursts (GRB) and active galactic nuclei (AGN) jets have been suggested as sources of high-energy, > 1014 eV, neutrinos, with fluxes that may be detectable with km2 high-energy neutrino detectors currently under construction. We show that cosmic-ray observations set a model independent upper bound of E2 < 2 × 10-8 GeV/cm2 s sr to the flux of high-energy neutrinos produced by photo-meson interaction in sources of size not much larger than the proton photo-meson mean-free-path, as is the case for both AGN jets and GRBs. This bound is two orders of magnitude below the flux predicted in some popular AGN jet models but is consistent with our predictions from GRB models. The predicted flux from GRBs is E2dN/dE ~ 0.3 × 10-8 GeV/cm2 s sr for 1014 eV < E < 1016 eV; we also derive the expected flux at higher energy. The upper bound derived here does not apply to the flux of neutrinos possibly produced in AGN cores, but there is no observational evidence from either photon or high-energy cosmic-ray studies to support the conjecture that high-energy neutrinos are produced in that environment.

High Energy Astrophysical Neutrinos: the Upper Bound is Robust

Authors: John Bahcall and Eli Waxman
Journal:Physical Review D, 64, 023002 (July 15, 2001); hep-ph/9902383.

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Abstract: We elucidate the physical basis for the upper bound on high energy neutrino fluxes implied by the observed cosmic ray flux. We stress that the bound is valid for neutrinos produced either by p, reactions or by p-p(n) reactions in sources which are optically thin for high energy protons to photo-meson and nucleon-meson interactions. We show that the upper bound is robust and conservative. The Waxman-Bahcall bound overestimates the most likely neutrino flux by a factor ~ 5/, for small optical depths . The upper limit cannot be plausibly evaded by invoking magnetic fields, optically thick AGNs, or large hidden fluxes of extragalactic protons. We describe the implications of the bound for future experiments including the AMANDA, ANTARES, Auger, ICECUBE, NESTOR, and OWL/AIRWATCH detectors.

Neutrino Afterglow from Gamma-Ray Bursts: ~ 1018 eV

Authors: Eli Waxman and John Bahcall
Journal:The Astrophysical Journal, 541, 707-711 (October 1, 2000), hep-ph/9909286.

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Abstract: We show that a significant fraction of the energy of a gamma-ray burst (GRB) is probably converted to a burst of 1017-1019 eV neutrinos and multiple GeV gammas that follow the main GRB by > 10 s. If, as previously suggested, GRB's accelerate protons to ~ 1020 eV, then both the neutrinos and the gammas may be detectable.

5-10 GeV Neutrinos from Gamma-Ray Burst Fireballs

Authors:John Bahcall and Peter Mészáros
Journal:Physical Review Letters, 85, 1362-1365 (14 August 2000). hep-ph/0004019.

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Abstract: A gamma-ray burst fireball is likely to contain an admixture of neutrons, in addition to protons, in essentially all progenitor scenarios. Inelastic collisions between differentially streaming protons and neutrons in the fireball produce muon neutrinos (antineutrinos) of ~ 10 GeV as well as electron neutrinos (antineutrinos) of ~ 5 GeV, which could produce ~ 7 events/year in kilometer cube detectors, if the neutron abundance is comparable to that of protons. Photons of ~ 10 GeV from pi-zero decay and ~ 100 MeV electron antineutrinos from neutron decay are also produced, but will be difficult to detect. Photons with energies < 1 MeV from shocks following neutron decay produce a characteristic signal which may be distinguishable from the proton-related MeV photons.

High Energy Neutrino Experiments

High Energy Neutrino Viewgraphs

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