The Pacific Ocean Neutrino Experiment: Site characterization, background studies and tau neutrino sensitivity

Abstract

The Pacific Ocean Neutrino Experiment (P-ONE) is a new neutrino telescope whose first detector phase is currently under construction. In this work, we study the properties of the site, characterize the detection elements of the first phase, and estimate the expected tau neutrino detection rates of the full P-ONE detector. Based on data from pathfinder missions, we measured the optical attenuation length of the water at the future detector site, with a maximum value of (27.7+1.9/-1.3) m at 450 nm. Using background rate measurements of radioactivity and bioluminescence, we extrapolated the trigger rates of future P-ONE modules and predict manageable rates for a threefold coincidence trigger. The Hamamatsu R14374 photomultiplier, which we characterized through a laser-based test stand, showed favourable properties and was chosen for the P-ONE modules. Combining these results, we explored a method to identify tau neutrinos using P-ONE's unique combination of water properties and waveform digitization. Initial simulations show a high sensitivity for events with a tau decay length above 12 m. We found an expected rate of 0.5±0.1 events per year, which is comparable to what has been achieved with current detectors. Further optimizations are required, as the results indicate that significant improvements are possible with a better algorithm, an optimized detector geometry, or faster readout electronics.