ABSTRACT
Having discussed neutrinos from stars with energies Eν < 100 MeV which have already been observed, we now want to discuss additional astrophysical neutrinos produced with much higher energy. The observation of cosmic rays with energies up to 1020 eV, by the Fly’s Eye, HiRes, AGASA and Auger air shower arrays, supports the possibility of also observing neutrinos up to this energy range. Neutrinos mostly originate from the decay of secondaries like pions resulting from “beam dump” interactions of protons with other protons or photons as in accelerator experiments. Like photons, neutrinos are not affected by a magnetic field. Even absorption which might affect photon detection is not an issue and this allows a search for hidden sources, which cannot be seen otherwise. Therefore, they are an excellent candidate for finding point sources in the sky and might help to identify the sources of cosmic rays. In addition, our view of the universe in photons is limited for energies beyond 1 TeV. The reason is the interaction of such photons with background photons γ+ γBG → e+e−. The reaction has a threshold of 4EγEγBG ≈ (2me)2. In this way TeV photons are attenuated due to reactions on the IR background and PeV photons by the cosmic microwave background (see Chapter 13). For additional literature see [Sok89,Gai90,Ber91,Lon92,94,Gai95,Lea00,Sch00,Gri01,Hal02,Aha03,Sta04, Blu¨09, Hin09, Anc09].
