Ultra-high-energy neutrinos are unique astrophysical messengers as they interact only weakly with intervening matter and can therefore be used to probe the distant universe. A small but observable flux of these ultra-high-energy neutrinos are expected to be produced in interactions between high-energy "cosmic ray" charged particles traveling through the Universe and Cosmic Microwave Background photons. Observations of these cosmogenic neutrinos probe the structure and evolution of the Universe and test physics at energies beyond the standard models. Utilizing the large volume of radio transparent ice, several pioneering efforts to detect these high energy neutrinos have been implemented in Antarctica. Ultra-high-energy neutrinos traveling through the dense Antarctic ice generate cascades of particles that emit observable radio waves. This award will support operations and continued development of the Hexagonal Radio Array (HRA), located on the surface of the Ross Ice Shelf in Antarctica. HRA is designed to detect short-duration radio pulses generated by neutrino interactions in the ice, which reflect from the ice-water surface at the bottom of the Ross Ice Shelf up to the stations on the surface. This award provides funding to improve the detector characterization and continue observations. The group will utilize a variety of outreach activities, including twitter feeds and personal blogs, to engage the public in the science.
Consisting of seven autonomous stations, HRA is intended to demonstrate the technology, assess data quality, and evaluate backgrounds as the first phase of a larger project, the Antarctic Ross Ice-shelf ANtenna Neutrino Array (ARIANNA.) With data from the HRA stations, the group will further characterize the sources and properties of non-thermal contributions, and improve the accuracy of detector simulation and event reconstruction programs.
