Description
Ultra-high-energy (UHE) neutrinos, with EeV-scale energies (1 EeV = 10^{18} eV), were first predicted more than fifty years ago. They are instrumental to revealing the long-sought origin of UHE cosmic rays and neutrino physics at the highest energies. Yet, they are rare; so far, they have escaped detection. Fortunately, a new generation of neutrino telescopes is being designed to discover UHE neutrinos in the next 10-20 years, even if their flux is tiny. We provide the first detailed discovery forecasts, geared to IceCube-Gen2, the planned upgrade of IceCube. To make our forecasts realistic and robust, we use state-of-the-art ingredients all-around: in the flux predictions, neutrino propagation inside Earth, cross sections, backgrounds, and detector geometry and response. Our forecasts are encouraging: optimistic fluxes (10-30 detected neutrinos per year) will be discovered right away; mid-size fluxes (< 10 neutrinos per year), within a year. With these rates, meaningful UHE astrophysics and particle-physics searches will be legitimately possible.
