The EHE Neutrino Search Capability of the IceCube Observatory

An initial study of the extremely high energy (EHE) physics capabilityof the IceCube neutrino observatory is demonstrated by considering a GZK mechanism neutrino production model, which is a guaranteed source for EHE neutrinos. We study EHE event properties in the energy range $10^{5}$ $<$ E $<$ $10^{11}$ GeV observed by IceCube using detailed Monte Carlo simulation. Results of a simulation study show that about 0.7 EHE neutrino events per year is expected with the full IceCube configuration over a 0.03 atmospheric muon background which passed an EHE event criteria. It is also shown that with the present partial IceCube detector with the same criteria is capable of studying EHE physics and the sensitivity improves with the number of deployed strings in the ice.Comment: Proceedings of the Cosmic Ray International Seminar (CRIS 2006) on UHECR: Status and Perspective

Constraints on the origin of the ultra-high energy cosmic-rays using cosmic diffuse neutrino flux limits: An analytical approach

Astrophysical neutrinos are expected to be produced in the interactions of ultra-high energy cosmic-rays with surrounding photons. The fluxes of the astrophysical neutrinos are highly dependent on the characteristics of the cosmic-ray sources, such as their cosmological distributions. We study possible constraints on the properties of cosmic-ray sources in a model-independent way using experimentally obtained diffuse neutrino flux above 100 PeV. The semi-analytic formula is derived to estimate the cosmogenic neutrino fluxes as functions of source evolution parameter and source extension in redshift. The obtained formula converts the upper-limits on the neutrino fluxes into the constraints on the cosmic-ray sources. It is found that the recently obtained upper-limit on the cosmogenic neutrinos by IceCube constrains the scenarios with strongly evolving ultra-high energy cosmic-ray sources, and the future limits from an 1 km^3 scale detector are able to further constrain the ultra-high energy cosmic-rays sources with evolutions comparable to the cosmic star formation rate.Comment: 9 pages, 3 figures and 1 table. Accepted by Phys. Rev.