In Search of Extraterrestrial High-Energy Neutrinos

We review the search for astrophysical neutrinos. We begin by summarizing the various theoretical predictions that correlate the expected neutrino flux with data from other messengers, specifically gamma rays and ultrahigh-energy cosmic rays. We then review the status and results of neutrino telescopes both in operation and decommissioned as well as the methods used for data analysis and background discrimination. Particular attention is devoted to the challenge enforced by the highly uncertain atmospheric muon and neutrino backgrounds in relation to searches of diffuse neutrino fluxes. Next, we examine the impact of existing limits on neutrino fluxes on studies of the chemical composition of cosmic rays. After that, we show not only that neutrinos have the potential to discover astrophysical sources, but also that the huge statistics of atmospheric muons can be a powerful tool. We end by discussing the prospects for indirect detection of dark matter with neutrino telescopes.