Novel Background Rejection Techniques in a Search for Ultra-high Energy Neutrinos Using an ARIANNA Detector Station at the South Pole

The ARIANNA detector array is a radio-based neutrino detector array consisting of autonomous, solar-powered stations separated by 1km. It is designed to detect neutrinos with energies above 1017eV that interact with the cold, transparent polar ice. An ARIANNA detector station located near the South Pole has been equipped with 4 downward-facing LPDAs, 2 upward-facing LPDAs, and 2 dipole antennas, and has been taking data from December 2018 to January 2021. We provide a preliminary report on the improvement in background rejection due to novel analysis techniques utilizing the newly added upward-facing LPDAs and dipole antennas.