Optimising Underwater Neutrino Telescopes for All-Flavour Point Source Sensitivity

TL;DR

This study evaluates how different design choices for underwater neutrino telescopes affect their ability to detect astrophysical sources, emphasizing the importance of optical properties and optimal array configuration.

Contribution

It provides a comparative performance analysis of various detector configurations for the proposed TRIDENT array, highlighting key factors for optimizing all-flavour neutrino detection.

Findings

Larger volume alone does not improve performance.

Taller strings offer modest gains within engineering limits.

Sea-water optical properties are crucial for detector layout optimization.

Abstract

High-energy neutrino astronomy has advanced rapidly in recent years, with IceCube, KM3NeT, and Baikal-GVD establishing a diffuse astrophysical flux and pointing to promising source candidates. These achievements mark the transition from first detections to detailed source studies, motivating next-generation detectors with larger volumes, improved angular resolution, and full neutrino-flavour sensitivity. We present a performance study of large underwater neutrino telescopes, taking the proposed TRIDENT array in the South China Sea as a case study, with a focus on comparing the performance of various detector configurations against the TRIDENT baseline design. Both track-like events primarily from muon neutrinos, which provide precise directional information, and cascade events from all flavours, which offer superior energy resolution, diffuse-source sensitivity, and all-sky flavour coverage, are included to achieve a balanced performance across source types. The time to discover potential astrophysical sources with both track- and cascade-like events is used as the figure of merit to compare a variety of detector design choices. Our results show that, for a fixed number of optical modules, simply enlarging the instrumented volume does not inherently lead to improved performance, while taller strings can provide modest gains across all detector channels, within engineering constraints. Distributing dense clusters of strings over a large volume is found to generally worsen discovery potential compared to the baseline layout. Finally, the optical properties of the sea-water emerge as the key factor dictating the optimisation of detector layout, highlighting the need for in-situ measurements and early deployment of optical modules to guide the final array configuration.