Speaker: Alan Salcedo Gomez

Host: Prof. Nepomuk Otte

Title: Little Red Dots as "Black Hole Stars”

Abstract:

Ultra-high-energy (UHE) neutrinos (Eν ≥ 10^17 eV) uniquely probe extreme astrophysical environments and fundamental physics, accessing energies beyond terrestrial accelerators. A recent candidate event reported by KM3NeT exemplified the growing potential of neutrinos in this regime.

The Askaryan Radio Array (ARA) searches for UHE neutrinos via impulsive radio emission from particle cascades in Antarctic ice, enabling large instrumented volumes with a sparse array. In this talk, I will present the first array-wide diffuse flux search with ARA using over a decade of data (2013–2023), incorporating extensive data-driven detector modeling and a full treatment of neutrino-induced lepton propagation, which enhances the detector acceptance at the highest energies. It also combines data of independently operating ARA detectors within a unified framework for signal processing and background rejection. This search will either identify the first UHE neutrino candidates observed by an in-ice radio detector or set the most stringent limits around O(10 EeV).

I will then discuss progress toward future precision astrophysics through polarization-based directional reconstruction, including the impact of birefringence in Antarctic ice. These advances will improve source identification, enable measurements of neutrino–nucleon cross sections, and allow tests of physics beyond the Standard Model, while laying the groundwork for next-generation arrays such as the under-construction RNO-G and planned IceCube-Gen2 Radio.