High energy diffuse background neutrinos in the Universe: from TeV to EeV

The Universe is filled with neutrinos. These diffuse neutrinos extend their presence far beyond the MeV energy range, encompassing much higher energies. The IceCube neutrino observatory has made groundbreaking discoveries in observing TeV to PeV energy neutrinos. Located at the South Pole, IceCube is a cubic-kilometer-scale deep-ice Cherenkov neutrino detector. Its cosmic neutrino searches span an energy spectrum ranging from below the TeV threshold to the EeV range and beyond.

In the TeV to PeV energy range, ongoing analyses are revealing the origins of these high-energy diffuse neutrinos through multi-messenger observations. Moving to the EeV energy range, we anticipate a flux of 'cosmogenic' neutrinos produced by interactions between ultra-high-energy cosmic rays and background radiation. The absence of EeV neutrino searches has allowed us to convert upper limits on neutrino flux into upper limits on potential sources of ultra-high-energy cosmic rays. In this presentation, I will discuss IceCube's research on diffuse astrophysical neutrino emissions in relation to point-like neutrino sources. Additionally, I will explore future prospects with IceCube-Gen2, the next-generation neutrino telescope at the South Pole.