International School of Cosmic Ray Astrophysics

16^th  Course: "Gamma Ray and Cosmic Ray Astrophysics: From below GeV to beyond EeV Energies"

 5-12 July 2008
Ettore Majorana Centre
Erice, Sicily, Italy

Topic: Search for High Energy Neutrinos with Detectors Deployed in Antarctic Ice
Lecturer: Andrea Silvestri

Current and next generation neutrino telescopes, such as AMANDA and IceCube, search primarily for very high energy (above TeV) neutrinos of cosmic origin. Candidates for extragalactic neutrino sources are thought to be AGN and GRBs, which might provide an accelerator mechanism of high-energy hadrons. We discuss techniques and detector performance for measuring detectable neutrino-induced muon rate with energy above TeV. We present results from the first search for Ultra High Energy (UHE) neutrinos performed on data collected in 2003 using TWR of the AMANDA experiment. A search for a diffusely distributed flux of UHE neutrinos shows no events, leading to a flux limit. The limit is the most stringent placed to date. A number of model predictions different from the E^-2 spectrum have been tested and some have been rejected at a 90% C.L. A search of the northern hemisphere for localized event clusters shows no statistically significant excess, thus a flux limit is calculated. We also show that UHE results can limit the flux from point sources in the southern sky. We present a model-dependent constraint on the extragalactic point flux that is determined from the diffuse flux limit. The model-dependent constraint on the point flux is a factor twenty lower than present experimental limits from direct searches. Finally, we show the current status of the IceCube detector, first analysis results, and discuss prospects and implications to search for diffuse and extra-galactic point fluxes with km^3 neutrino telescopes.