Title: Radio Detection of Ultra-High-Energy Neutrinos in Evolving Polar Ice
Speaker: Alexander Kyriacou (U of Kansas)
Abstract:
Ultra-high-energy neutrinos (UHENs) may reveal the origin of the highest-energy cosmic rays and provide a unique window into physics beyond the Standard Model. Their detection requires fiducial volumes orders of magnitude greater than those of current gigaton-scale neutrino observatories. Several experiments therefore aim to monitor the polar ice sheets for radio signatures of UHEN interactions, either through radio Cherenkov emission from in-ice particle cascades or via radar reflections from ionization trails left in their wake. These signals often propagate through the upper 100–200 m of compacting snow, known as firn, whose density and refractive index increase with depth and evolve over time due to accumulation, temperature variability, and episodic melt events. In this seminar, I present a study of the time-dependent evolution of the firn layer and its impact on radio signal propagation. By incorporating evolving firn density into radio propagation simulations, we quantify how this evolution modulates signal spectra, amplitudes, travel times, and propagation paths. In the absence of an up-to-date ice model, these effects introduce an irreducible systematic uncertainty in neutrino energy and direction reconstruction. Given the ongoing warming of polar regions, understanding and mitigating these effects is a crucial consideration for radio- and radar-based UHEN detectors. I also present preliminary measurements of ice properties and radio propagation obtained at Summit Station during the 2024 summer deployment of the Radar Echo Telescope experiment.