The Potential of Spaced-based High-Energy Neutrino Measurements via the Airshower Cherenkov Signal

TL;DR

This paper explores the potential for space-based detectors to observe high-energy neutrino airshowers via Cherenkov signals, highlighting the lower energy thresholds and event rates achievable compared to fluorescence detection.

Contribution

It introduces a simulation framework for Cherenkov signal detection of upward airshowers and estimates the observable neutrino event rate for space-based experiments.

Findings

Cherenkov signals can be observed at energies above 10^16.5 eV.

Neutrino attenuation limits the effective detection area to ~3x10^5 km^2.

Estimated cosmogenic neutrino detection rate is about 1 event per year.

Abstract

Future space-based experiments, such as OWL and JEM-EUSO, view large atmospheric and terrestrial neutrino targets. With energy thresholds slightly above 10^19 eV for observing airshowers via air fluorescence, the potential for observing the cosmogenic neutrino flux associated with the GZK effect is limited. However, the forward Cherenkov signal associated with the airshower can be observed at much lower energies. A simulation was developed to determine the Cherenkov signal strength and spatial extent at low-Earth orbit for upward-moving airshowers. A model of tau neutrino interactions in the Earth was employed to determine the event rate of interactions that yielded a tau lepton which would induce an upward-moving airshower observable by a space-based instrument. The effect of neutrino attenuation by the Earth forces the viewing of the Earth's limb to observe the nu_tau-induced Cherenkov airshower signal at above the OWL Cherenkov energy threshold of ~10^16.5 eV for limb-viewed events. Furthermore, the neutrino attenuation limits the effective terrestrial neutrino target area to ~3x10^5 km^2 at 10^17 eV, for an orbit of 1000 km and an instrumental full Field-of-View of 45 degrees. This translates into an observable cosmogenic neutrino event rate of ~1/year based upon two different models of the cosmogenic neutrino flux, assuming neutrino oscillations and a 10% duty cycle for observation.