Downward ultra-high-energy neutrino detection in the air with radio antennas at ground-based observatories

TL;DR

This paper introduces a radio detection method for ultra-high-energy neutrinos using ground-based antennas, demonstrating improved sensitivity and reconstruction capabilities for inclined air showers, applicable to future observatories.

Contribution

A new reconstruction algorithm based on radio emission maximum ($X^{ ext{radio}}_{ ext{max}}$) for identifying neutrino-induced air showers from simulations.

Findings

Radio detection enhances sensitivity to inclined showers above 1 EeV.

The method effectively distinguishes neutrino showers from cosmic ray background.

Simulation results show promising trigger efficiency and reconstruction performance.

Abstract

Ultra-high-energy (UHE) neutrinos are unique cosmic messengers that can traverse cosmological distances unattenuated, providing direct insight into the most energetic processes in the universe. Radio detection offers significant advantages for detecting highly inclined air showers induced by UHE neutrinos. This is due to a larger exposure range compared to particle detectors, which is a result of minimal atmospheric attenuation of radio signals combined with good reconstruction precision. Furthermore, this technique improves the air shower longitudinal reconstruction, which can be used to identify neutrinos with their first interaction far below the top of the atmosphere. In this work, we present a method for identifying UHE neutrinos using ground-based radio antennas. A reconstruction algorithm is introduced based on the radio emission maximum ($X^{\text{radio}}_{\text{max}}$), which demonstrates its power in distinguishing deeply developing neutrino-induced showers from background cosmic rays. Using simulations of $\nu_e$-CC-induced air showers, we evaluate the trigger efficiency, reconstruction performance, and resulting effective area and aperture prediction for a reference array. Our results show that radio detection significantly enhances the sensitivity to very inclined showers above 1 EeV, complementing traditional surface detectors. This technique is highly scalable and applicable to future radio observatories, such as GRAND. The proposed reconstruction and identification strategy provides a pathway toward achieving the sensitivity required to detect UHE neutrinos.