Diffuse neutrino emissions from the Southern sky and Mediterranean neutrino telescopes

Astrophysical high-energy neutrinos offer an extremely interesting window of observation on our Universe. Cosmic neutrinos are probes for extreme events happening nearby the most powerful astrophysical objects. Direct information on the behaviour of cosmic ray sources is provided by neutrinos: since they are weakly interacting neutral particles, barely changing their information load over cosmic distance, the detection of neutrinos from the interaction of primary cosmic rays close to their acceleration site could allow the identification of their sources and of their production and acceleration mechanisms. Compelling evidence for the existence of an astrophysical flux of neutrinos above some tens of TeV has been reported by the IceCube Collaboration. Some features of the energy and declination distributions of the IceCube signal hint at a North/South asymmetry of the measured neutrino flux, which could be related to the presence of the bulk of our Galaxy in the Southern hemisphere. The ANTARES neutrino telescope, operating in the Mediterranean Sea since 2007, offers the best sensitivity to muon neutrinos below 100TeV in this part of the sky. This allows the detector to focus on the neutrino flux produced by galactic cosmic ray interactions in the bulk of the Milky Way. Studies on possible neutrino signals using ANTARES data collected are reported in this paper, as well as the prospects for the next-generation neutrino telescope, KM3NeT/ARCA, to be built in the Mediterranean Sea. In particular, ANTARES can already test the propagation mechanisms of cosmic rays in the Milky Way by constraining the contribution from the Galactic Plane to the total neutrino flux observed by IceCube. The KM3NeT/ARCA detector will then allow the detailed study of galactic neutrino fluxes.