Triboelectric Backgrounds to radio-based UHE Neutrino Exeperiments

TL;DR

This paper investigates how triboelectric effects, caused by wind over snow surfaces, can generate RF backgrounds that mimic neutrino signals in radio-based ultra-high-energy neutrino detection experiments like IceCube-Gen2.

Contribution

It identifies and characterizes triboelectric backgrounds as a potential source of false signals in radio neutrino experiments, highlighting their spectral and environmental features.

Findings

Triboelectric backgrounds are evident in multiple neutrino experiments.

A threshold wind velocity (~10 m/s) influences background occurrence.

Discharges tend to originate from above-surface structures.

Abstract

The proposed IceCube-Gen2 (ICG2) seeks to instrument ~500 sq. km of Antarctic ice near the geographic South Pole with radio antennas, in order to observe the highest energy (E>1 EeV) neutrinos in the Universe. To this end, ICG2 will use the impulsive radio-frequency (RF) signal produced by neutrino interactions in polar ice caps. In such experiments, rare single event candidates must be unambiguously separated from background; to date, signal identification strategies primarily reject thermal noise and anthropogenic backgrounds. Here, we consider the possibility that fake neutrino signals may also be naturally generated via the 'triboelectric effect'. This broadly includes any process in which force applied at a boundary layer results in displacement of surface charge, generating a potential difference {\Delta}V. Wind blowing over granular surfaces such as snow can induce such a {\Delta}V, with subsequent discharge. Discharges over nanosecond-timescales can then lead to RF emissions at characteristic MHz-GHz frequencies. We find that such backgrounds are evident in the several neutrino experiments considered, and are generally characterized by: a) a threshold wind velocity which likely depends on the experimental signal trigger threshold and layout; for the experiments considered herein, this value is typically O(10 m/s), b) frequency spectra generally shifted to the low-end of the frequency regime to which current radio experiments are typically sensitive (100-200 MHz), c) for the strongest background signals, an apparent preference for discharges from above-surface structures, although the presence of more isotropic, lower amplitude triboelectric discharges cannot be excluded.