Neutrino astronomy with km3 underwater and under ice

Abstract

High energy neutrinos are considered optimal probes to identify the sources of high energy cosmic rays. Many indications suggest, indeed, that cosmic objects, where acceleration of charged particles take place are the sources of the detected UHECRs, the same sources should also produce high energy neutrino fluxes. Indeed, pγ or pp interactions responsible for > TeV neutrinos and γ rays fluxes, are expected to occur in several astrophysical environments. In Supernova Remnants (SNRs) protons, accelerated through Fermi mechanism, can interact with gas in dense SN shells or molecular clouds, producing both neutral and charged pions. Decay of neutral pion originates gamma rays. The observation of ≃ 10TeV gamma rays from Supernova Remnant RXJ1713.7-3946 claimed by CANGAROO [1], seems to validate this hypothesis, but the result is still under discussion. The neutrino flux, produced by charged pion decay, is expected to be similar to the hadronic high energy gamma rays one. Results from the HESS air Cerenkov Telescope, concerning the observation of TeV gamma ray from the Sgr A* region (the Galactic centre), show an ∝ E −2.2 γ ray spectrum that could be originated by hadronic interactions, an interpretation which also implies the production of intense high energy neutrino fluxes [2]. Photo-meson (pγ) interactions can occur in astrophysical environments that show dense low energy photons fields: microquasar jets, AGNs and in GRBs are examples.