[Paper Review] Trinity: An Air-Shower Imaging Instrument to detect Ultrahigh Energy Neutrinos

A. N. Otte, A. M. Brown+8 more|arXiv (Cornell University)|Jul 19, 2019

Astrophysics and Cosmic Phenomena8 citations

TL;DR

Trinity proposes a ground-based air-shower imaging telescope array to detect ultrahigh-energy (UHE) tau neutrinos in the 10^7–10^10 GeV energy range using atmospheric Cherenkov light detection. By leveraging proven imaging techniques from gamma-ray and cosmic-ray experiments, Trinity aims to achieve a differential sensitivity of ~10^{-9} GeV cm^{-2} s^{-1} sr^{-1}, enabling breakthroughs in multimessenger astrophysics, UHECR source and composition studies, and tests of new physics beyond the Standard Model.

ABSTRACT

Trinity is a proposed air-shower imaging system optimized for the detection of earth-skimming ultrahigh energy tau neutrinos with energies between $10^7$ GeV and $10^{10}$ GeV. Trinity will pursue three major scientific objectives. 1) It will narrow in on possible source classes responsible for the astrophysical neutrino flux measured by IceCube. 2) It will help find the sources of ultrahigh-energy cosmic rays (UHECR) and understand the composition of UHECR. 3) It will test fundamental neutrino physics at the highest energies. Trinity uses the imaging technique, which is well established and successfully used by the very high-energy gamma-ray community (CTA, H.E.S.S., MAGIC, and VERITAS) and the UHECR community (Telescope Array, Pierre Auger)

Motivation & Objective

• To identify the astrophysical sources responsible for the IceCube-observed astrophysical neutrino flux by extending spectral measurements into the ultrahigh-energy (UHE) band.
• To constrain the composition and sources of ultrahigh-energy cosmic rays (UHECRs) by combining UHE neutrino data with gamma-ray and cosmic-ray observations in a multimessenger framework.
• To probe fundamental neutrino physics at the highest energies, including potential deviations from the Standard Model such as enhanced neutrino cross sections or signatures from superheavy dark matter.
• To achieve a differential sensitivity of ~10^{-9} GeV cm^{-2} s^{-1} sr^{-1} in the UHE band, enabling detection of cosmogenic and source-originated neutrino fluxes.

Proposed method

• Trinity employs an array of six wide-field, ground-based telescopes equipped with large-aperture optics and silicon photomultiplier (SiPM) cameras to image Cherenkov light from extensive air showers initiated by earth-skimming tau neutrinos.
• The telescopes use a novel MACHETE optics design with a 0.3° angular resolution, optimized for detecting the lateral and temporal structure of air showers from UHE neutrino interactions.
• A custom front-end electronics system based on the MUSIC chip and AGET readout architecture enables low-cost, high-bandwidth signal acquisition with ~$100 per channel, totaling $2M for 20,000 channels.
• The light-collecting mirrors are fabricated using thin-film glass replica technology, achieving a point spread function of 0.05°, well below the required resolution.
• On-site computing infrastructure uses a redundant server setup for real-time data acquisition and control, with minimal storage needs and estimated costs of $100,000.
• The system is designed for remote operation with only periodic on-site maintenance visits, minimizing long-term operational costs.

Experimental results

Research questions

• RQ1 What are the astrophysical sources of the high-energy neutrinos detected by IceCube, and how do they connect to UHE cosmic rays and gamma-ray sources?
• RQ2 How can UHE neutrino observations constrain the composition and source evolution of ultrahigh-energy cosmic rays, especially during the galactic-extragalactic transition?
• RQ3 Can UHE neutrino data reveal signatures of new physics beyond the Standard Model, such as enhanced neutrino cross sections or superheavy dark matter decays?
• RQ4 What is the relative contribution of cosmogenic neutrinos (from UHECR interactions with CMB photons) versus direct source neutrinos in the UHE band?
• RQ5 How do the flavor composition and angular distribution of UHE neutrinos compare with predictions from current source models?

Key findings

• Trinity achieves a differential sensitivity of ~10^{-9} GeV cm^{-2} s^{-1} sr^{-1} in the 10^7–10^10 GeV energy range, sufficient to probe benchmark fluxes from UHECR sources and cosmogenic neutrinos.
• The cost estimate for constructing six telescopes is $4.5 million, with $2M allocated to cameras and readout, $1M to optics, $100K to on-site computing, and $1.4M to infrastructure.
• The camera system uses commercially available SiPMs and the MUSIC chip, enabling a per-channel cost of $100, resulting in a total camera cost of $2M for 20,000 channels.
• Mirror technology based on thin-film glass replica produces 1.5m diameter mirrors with a 0.05° point spread function, exceeding the required 0.3° resolution of the MACHETE optics.
• Operational costs are estimated at $950,000 per year, covering 6 graduate students, 4 postdoctoral researchers, technical support, travel, and maintenance, with remote operation minimizing on-site staffing.
• Decommissioning costs are estimated at $400,000, with no unusual environmental or logistical challenges expected.