Near-future discovery of point sources of ultra-high-energy neutrinos

TL;DR

This paper forecasts the potential discovery of ultra-high-energy neutrino point sources with upcoming radio-detection telescopes, emphasizing the importance of source identification for understanding cosmic ray origins.

Contribution

It presents state-of-the-art forecasts for detecting UHE neutrino sources, incorporating detector response and background uncertainties, to guide future neutrino telescope designs.

Findings

Sources at certain declinations are easier to detect.

Discovery of one steady source implies high neutrino luminosity.

Non-detection of transients constrains their luminosity and prevalence.

Abstract

Upcoming neutrino telescopes may discover ultra-high-energy (UHE) cosmic neutrinos, with energies beyond 100 PeV, in the next 10-20 years. Finding their sources would identify guaranteed sites of interaction of UHE cosmic rays, whose origin is unknown. We search for sources by looking for multiplets of UHE neutrinos arriving from similar directions. Our forecasts are state-of-the-art, geared at neutrino radio-detection in IceCube-Gen2. They account for detector energy and angular response, and for critical, but uncertain backgrounds. Sources at declination of $-45^\circ$ to $0^\circ$ will be easiest to discover. Discovering even one steady-state source in 10 years would imply that the source has an UHE neutrino luminosity at least larger than about $10^{43}$ erg/s (depending on the source redshift evolution). Discovering no transient source would disfavor transient sources brighter than $10^{53}$ erg as dominant. Our results aim to inform the design of upcoming detectors.