Jiangmen Underground Neutrino Observatory (JUNO)

Why is it in the News?

The Jiangmen Underground Neutrino Observatory (JUNO) collaboration recently published its first scientific results, including highly precise measurements of how neutrinos produced by nuclear reactors change their flavour (oscillate) while travelling.

About JUNO

• The Jiangmen Underground Neutrino Observatory (JUNO) is a large underground neutrino research facility located near Kaiping in Guangdong Province, China.

• It is one of the world's most advanced experiments dedicated to studying neutrinos and is regarded as a next-generation neutrino observatory.

• JUNO is the outcome of an international scientific collaboration involving 74 research institutions from Asia, Europe, and the Americas, with nearly 700 scientists participating in the project.

• The observatory is led by the Chinese Academy of Sciences (CAS) through its Institute of High Energy Physics (IHEP).

• It is China's second major neutrino experiment, following the successful Daya Bay Reactor Neutrino Experiment.

Location and Infrastructure

• JUNO has been strategically established approximately 53 kilometres from the Taishan and Yangjiang Nuclear Power Plants. These reactors continuously produce a large number of electron antineutrinos, making them ideal sources for precision neutrino studies.

• The observatory is constructed 700 metres beneath the Earth's surface, which shields the detector from cosmic radiation and other background noise.

• The underground experimental hall measures nearly 80 metres in height and 50 metres in diameter, providing space for one of the world's most sophisticated neutrino detectors.

• Its central component is a 35-metre-radius spherical detector filled with nearly 20,000 tonnes of ultra-pure liquid scintillator.

• This makes JUNO the largest and highest-precision liquid scintillator detector ever built. The observatory has been designed for an operational lifespan of nearly 30 years, enabling continuous long-term scientific research.

Primary Scientific Objective

The principal objective of JUNO is to determine the Neutrino Mass Ordering (NMO), one of the most important unresolved questions in modern particle physics.

Scientists aim to achieve this by precisely measuring the oscillation pattern of electron antineutrinos emitted from nearby nuclear power reactors. By analysing how these neutrinos change from one flavour to another during their journey, researchers hope to determine the correct sequence of neutrino masses, thereby improving our understanding of the Standard Model of Particle Physics.

Technology Used

JUNO employs an extremely sensitive liquid scintillator detector capable of detecting the faint flashes of light produced when neutrinos interact with atoms inside the detector.

The enormous detector volume, combined with thousands of highly sensitive photomultiplier tubes (PMTs), enables the experiment to measure neutrino energies with unprecedented precision. The underground location further enhances accuracy by minimizing interference from cosmic rays.

Global Importance of JUNO

JUNO is regarded as one of the three next-generation neutrino observatories leading global research in neutrino physics. Along with Hyper-Kamiokande in Japan and the Deep Underground Neutrino Experiment (DUNE) in the United States, it represents the next generation of large-scale international particle physics experiments.

What are Neutrinos?

• Neutrinos are extremely small elementary particles belonging to the lepton family in the Standard Model of Particle Physics.

• They are commonly known as "Ghost Particles" because they interact only very weakly with matter, allowing them to pass through almost any object without being detected.

• Neutrinos possess no electric charge and have an extremely small mass, less than one millionth of the mass of an electron.

• They travel at speeds very close to the speed of light, making them among the fastest known particles in nature.

• Although Wolfgang Pauli first predicted the existence of neutrinos in 1930, they were experimentally discovered only in 1956, highlighting the extraordinary difficulty involved in detecting them.

Interaction with Fundamental Forces

Among the four fundamental forces of nature, neutrinos interact only through the Weak Nuclear Force and Gravity. They do not experience the Electromagnetic Force because they carry no electric charge, nor do they participate in the Strong Nuclear Force that binds atomic nuclei.

This extremely weak interaction explains why nearly 100 trillion neutrinos pass through the human body every second without causing any noticeable effect.

Sources of Neutrinos

Neutrinos are produced in a wide variety of natural and artificial processes. They originate from nuclear reactions inside the Sun, supernova explosions, radioactive decay, cosmic rays, nuclear reactors, and various other high-energy astrophysical events.

They are generally created when heavy particles decay into lighter particles, making them among the most abundant particles in the Universe.

Significance of Neutrino Research

The study of neutrinos is crucial for advancing our understanding of particle physics, stellar evolution, black holes, and the origin of the Universe. Precise measurements of neutrino properties may help explain why matter dominates over antimatter in the Universe and provide new insights into the Big Bang and the evolution of the cosmos.

The scientific discoveries made by experiments such as JUNO are therefore expected to reshape our understanding of the Universe at its most fundamental level.