Performance and Simulation of the ARIANNA Pilot Array, with Implications for Future Ultra-high Energy Neutrino Astronomy
The ARIANNA pilot Hexagonal Radio Array (HRA), a seven station test-bed for the development of an ultra-high energy (UHE) neutrino telescope, using Antarctica's Ross Ice Shelf as a detector, was completed during the 2014-2015 Antarctic summer season. In the more than three years since, the HRA has demonstrated remarkable resilience and stability, operating with a typical 90% uptime during the summer months using solar energy, and surviving multiple Antarctic winters. Novel wind turbine design has, for the first time, enabled the operation of an autonomous station in Moore's Bay over winter. The ARIANNA data acquisition system, built on the Synchronous Sampling plus Triggering (SST) circuitry developed at UCI, has proven to be capable and cost/power efficient. Beyond the HRA, hardware research and development has been ongoing, with a new revision of the SST system seeing service in a variety of specialized stations. Dedicated cosmic ray stations have successfully self-triggered and measured the flux of UHE cosmic ray air showers in broadband radio frequencies, which serves as an important calibration source for the neutrino analysis. In an international collaboration with the National Taiwan University, the ARIANNA Horizontal Cosmic Ray station, designed to measure air showers resulting from the interaction of ν τ in the surrounding mountains, was deployed and deployed.
The sensitivity of this fully autonomous array was simulated using the ShelfMC Monte Carlo, which has been developed to version 2.0, with significant improvements to accuracy and flexibility. A prototype analysis is presented which achieves 84.63% analysis efficiency while rejecting all measured non-cosmic ray backgrounds over a 1.5 year dataset for all HRA stations. The actualized livetime of 145 days per year per station is used to to construct a 5 year projection for an array of 300 ARIANNA stations. Results indicate that reasonable optimizations will allow such an array to probe or measure all but the most pessimistic models of the GZK neutrino flux. Lessons learned from the deployment and operation of the HRA will inform the design of the next generation of UHE radio neutrino detectors, which will provide insight into long standing questions on the nature and origin of the Universe's highest energy particles.