The EYE Neutrino Telescope: Conceptual Design Report
The EYE neutrino telescope project proposes utilizing an existing pit at South Korea's Yemilab to conduct groundbreaking investigations into sterile neutrinos, solar neutrino "up-turns," and the first oscillation minimum through real-time studies of ultra-high-intensity neutrino beams.
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Deep beneath the surface of the Earth, where the rock is thick enough to block the constant rain of particles from space, scientists are preparing to install a new kind of eye. This instrument is designed to watch for neutrinos, the most elusive of all known particles. These tiny particles, which have almost no mass and no electric charge, pass through ordinary matter as if it were not there. A single neutrino could travel through a wall of lead a light-year thick without ever hitting a single atom. Because they interact so rarely, catching them requires detectors of immense size and extreme sensitivity. Neutrinos are produced in the nuclear furnaces of stars, in the hearts of nuclear reactors, and in the radioactive decay of elements deep within the Earth. By studying them, scientists hope to answer fundamental questions about the universe, such as why the Sun shines, how the Earth generates its internal heat, and whether there are hidden types of particles that have never been seen before.
A new proposal called the νEYE project aims to build such a detector in a deep underground laboratory in South Korea. The plan, detailed in a recent conceptual design report, outlines how a massive tank of liquid scintillator—a special, glowing oil—will be placed in a deep pit to act as a giant trap for these ghostly particles. The project is not just about building a bigger version of existing detectors; it is about creating a unique environment where a high-intensity beam of particles can be generated right next to the detector, deep underground. This setup allows researchers to study neutrinos with a precision that has never been possible before, potentially revealing new physics that lies beyond our current understanding of the universe.
The core of the νEYE experiment is a two-part strategy involving both a massive detector and a powerful particle accelerator. The detector itself will hold roughly two thousand tonnes of liquid scintillator, a substance that flashes with light when a particle interacts with it. This tank will be surrounded by a buffer of water and then a larger outer tank of water, all designed to shield the sensitive inner core from natural radioactivity and cosmic rays. The liquid inside is so pure that it must be free of even the tiniest traces of radioactive contamination, which would otherwise drown out the faint signals from neutrinos. To achieve this, the team plans to build a sophisticated purification facility right next to the detector to clean the liquid to an extraordinary degree.
What makes νEYE unique is its location and its ability to work with a specific type of particle source called IsoDAR. While most neutrino experiments rely on natural sources like the Sun or distant nuclear reactors, or on accelerators built on the surface, νEYE proposes to install a compact particle accelerator in a tunnel right next to the detector, deep underground. This accelerator would fire a beam of protons at a target to create a flood of antineutrinos. Because the accelerator is underground, the detector can be much larger and more sensitive than surface-based experiments, which must be kept small to avoid being overwhelmed by cosmic radiation. This combination of a huge, ultra-pure detector and a nearby, intense beam of particles creates a laboratory for studying neutrino behavior in ways that were previously impossible.
One of the primary goals of the experiment is to search for a hypothetical particle known as a sterile neutrino. For decades, scientists have observed strange patterns in neutrino data that suggest there might be a fourth type of neutrino that does not interact with matter through any of the known forces, except perhaps gravity. This idea has been controversial, with some experiments seeing hints of it and others finding nothing. The νEYE team plans to use their intense beam of antineutrinos to look for a specific pattern of disappearance that would confirm the existence of this sterile particle. They also plan to test this using powerful radioactive sources placed directly inside or near the detector, providing a real-time check on previous results that relied on chemical analysis. If found, a sterile neutrino would be a monumental discovery, forcing a rewrite of the standard model of particle physics.
Beyond the search for new particles, the detector will act as a powerful telescope for the Sun and the Earth. By observing neutrinos coming from the Sun, the experiment aims to settle a long-standing debate about the Sun's composition, specifically the abundance of heavy elements like carbon and oxygen. The team also plans to measure the survival probability of solar neutrinos with unprecedented precision, looking for a specific change in their behavior that would confirm our current theories about how neutrinos change as they travel. Additionally, the detector will be able to sense neutrinos produced by the radioactive decay of uranium and thorium inside the Earth, offering a new way to map the planet's internal heat and structure. It will also serve as an early warning system for supernovae, capable of detecting the burst of neutrinos from a dying star in our galaxy before the light of the explosion reaches Earth.
The path to building this facility involves a careful, phased approach. The team has already begun constructing a one-tonne prototype detector in the same underground hall to test the technology and refine the design. This smaller version will help them understand the background noise in the environment and verify that their purification systems can produce liquid clean enough for the full-scale experiment. Once the prototype is successful, they will move to a phase where the detector is filled with water to test the electronics and timing systems. Only after these steps are complete will they fill the massive tank with the final liquid scintillator and begin the main physics program.
The project represents a significant collaboration between scientists from South Korea, the United States, Europe, and other countries. It leverages the existing infrastructure of the Yemilab underground facility, which already has the deep pit and tunnels needed for such a large experiment. By integrating a high-power accelerator with a massive neutrino detector, νEYE aims to open a new window into the subatomic world. Whether it confirms the existence of sterile neutrinos, solves the mystery of the Sun's metallicity, or reveals new interactions between particles, the experiment is poised to provide answers to some of the most pressing questions in modern physics. The work is a testament to the power of international cooperation and the relentless human drive to look deeper into the nature of reality.
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