Neutrinos are the most elusive particles of nature. They were first described from a theoretical standpoint in 1930 by the Austrian physicist Wolfgang Ernst Pauli, one of the pioneers of quantum physics. Among his many contributions is the well-known Pauli Exclusion Principle. However, their experimental discovery didn’t occur until 1956, thanks to American physicists Frederick Reines and Clyde Cowan.
The main reason these particles are so hard to detect is their minimal interaction with ordinary matter. They have a very tiny mass, no electric charge, and they are unaffected by both the strong nuclear interaction and electromagnetic force. Yet, they do respond to gravity and weak nuclear interactions. Indeed, they are highly unique particles.
Scientists often illustrate the difficulty of capturing a neutrino by explaining that every second, trillions of these particles pass through both the Earth and our bodies without colliding with any other particle. They further emphasize this elusiveness by using quantum mechanics, suggesting that one would need to create a lead plate one light-year thick to ensure that half of the neutrinos passing through it would interact with the lead’s particles.
The Jiangmen Observatory is Ready to Hunt Neutrinos
Despite their rarity, several observatories around the world are equipped to detect neutrinos. One notable example is the Japanese Super-Kamiokande, located in Hida, a city in central Honshu, Japan’s largest island. This massive facility is built in a mine situated 1 km deep and measures 40 meters in height and width, giving it the volume comparable to a fifteen-story building.
However, the true protagonist of this article is the Jiangmen Underground Neutrino Observatory (JUNO) located in the Chinese province of Guangdong. Much like Japan’s Super-Kamiokande, JUNO is an engineering marvel. Its centerpiece is a cylindrical pool 44 meters deep, housed in an underground chamber with granite walls that significantly minimize background noise.
The neutrino detector comprises a 41.1-meter diameter stainless steel mesh supporting a 35.4-meter diameter acrylic sphere.
The neutrino detector is constructed with a 41.1-meter-diameter stainless steel mesh that supports an acrylic sphere measuring 35.4 meters in diameter. This container is filled with an exotic liquid specifically designed to interact with neutrinos, producing detectable light in the process. JUNO is home to a staggering 20,000 tons of this liquid, confidently establishing itself as the largest neutrino detector globally.
The composition of this liquid aims to maximize the light generated by each neutrino interaction. It consists of three main components: linear alkyl benzene, serving as a solvent; 2,5-diphenyloxazole, which becomes excited when a neutrino interacts with it, emitting a flash of light; and lastly, 1.4-bis(2-methylstyryl)benzene, which absorbs the ultraviolet light emitted by 2,5-diphenyloxazole and re-emits it at a longer wavelength, easier to detect.
These flashes of light are captured by 45,000 photomultiplier tubes lining the inner surface of the sphere. By analyzing the intensity, position, and duration of these light flashes, scientists can reconstruct the trajectory and energy of each neutrino. Juno spokesperson Wang Yifang articulates the significance of this research, stating, “This observatory will allow scientists to address fundamental questions about the nature of matter and the universe.” Indeed, the implications could reshape our understanding of the cosmos.
Image | Generated by Xataka with Google Gemini
More information can be found at a relevant source like Digital Diario.
Furthermore, insights into particle physics are set to expand with projects like CERN’s future circular collider, projected to cost around €20 billion, and the potential discoveries it might lead to.