A Search for the Origin of Ultra-High Energy Neutrinos with ANITA-4

• Main Author: Batten, Luke
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UCL (University College London) 2022
• Subjects: Antarctic; The Antarctic; Antarc*; Ice Sheet
• Online Access: https://discovery.ucl.ac.uk/id/eprint/10144693/1/Batten_thesis.pdf; https://discovery.ucl.ac.uk/id/eprint/10144693/

The ANtarctic Impulsive Transient Antenna (ANITA) aims to detect Askaryan radio signatures from ultra-high energy (UHE) neutrinos interacting with the Antarctic ice sheet. However, the origin of neutrinos of such high energies is mostly unknown. This thesis contains a method for finding the potential astrophysical origin of UHE neutrinos, and includes the simulation and analysis used throughout the source search. The thesis also discusses the essential physics, the components of the experiment, and the details of the fourth flight of the ANITA experiment, ANITA-4. Though the source search itself was conducted for this specific flight, the methods presented can be applied to any previous or future flights. As such experiments are not yet sensitive enough to obtain a large dataset of UHE neutrinos, the sub-threshold events detected by ANITA-4 were projected back to the sky. The spatiotemporal proximity of such events were compared to the activity of several objects. Three classes of objects were studied: blazars, gamma-ray bursts (GRBs), and supernovae (SNe). A single object, the flaring blazar known as PKS 1502+106, showed an excess of events pointing back to it, exceeding the 99% confidence level threshold. Such searches and analyses are not yet sensitive enough to detect a high number of ultra-high energy neutrinos, and thus cannot directly point them back to their potential astrophysical origins. However, the sub-threshold analysis conducted in this thesis motivates future source search investigations, especially with the increase in sensitivity of upcoming experiments.