JUNO experiment

JUNO experiment
Name	JUNO
Experiment type	Neutrino observatory
Location	Jiangmen, Guangdong, China
Organization	Institute of High Energy Physics, Chinese Academy of Sciences

JUNO experiment. The Jiangmen Underground Neutrino Observatory is a next-generation liquid scintillator detector under construction in southern China. Designed as a multipurpose neutrino observatory, its primary physics goal is the determination of the neutrino mass ordering. The facility represents a major international collaboration in the field of particle physics and nuclear physics.

Overview

Located in an underground laboratory near Jiangmen in Guangdong province, the JUNO detector is positioned approximately 53 kilometers from both the Yangjiang Nuclear Power Plant and the Taishan Nuclear Power Plant. This strategic location optimizes its sensitivity to reactor antineutrinos. The project was formally initiated following extensive research and development efforts led by the Institute of High Energy Physics of the Chinese Academy of Sciences. Major construction milestones were achieved with support from international partners like the European Organization for Nuclear Research and various national funding agencies. Upon completion, it will be one of the largest and most sensitive detectors of its kind, joining other major global facilities such as the Super-Kamiokande in Japan and the Sudbury Neutrino Observatory in Canada.

Scientific goals

The flagship objective is the resolution of the neutrino mass ordering, a fundamental unknown in the Standard Model of particle physics. This will be achieved by precisely measuring the energy spectrum of electron antineutrinos emitted from the powerful reactor complexes at Taishan Nuclear Power Plant. Secondary goals include high-precision measurements of oscillation parameters like theta12 and Deltam21^2, surpassing the accuracy of previous experiments like Daya Bay Reactor Neutrino Experiment and KamLAND. Furthermore, JUNO aims to conduct a broad program including the detection of solar neutrinos, atmospheric neutrinos, geoneutrinos, and the search for proton decay and supernova relic neutrinos, contributing to astrophysics and cosmology.

Experimental design

The experimental design centers on a central detector containing 20,000 tons of liquid scintillator within an acrylic sphere, providing an ultra-pure target for neutrino interactions. This sphere is submerged in a large water pool equipped with photomultiplier tubes to act as a Cherenkov detector for vetoing cosmic muons. The entire apparatus is shielded by 700 meters of rock overburden at the Jiangmen Underground Laboratory, drastically reducing the cosmic ray background. The design emphasizes unprecedented energy resolution, targeting 3% at 1 MeV, which is critical for distinguishing the subtle interference patterns caused by neutrino mass ordering. This approach builds upon technologies pioneered by earlier experiments including Borexino at the Gran Sasso National Laboratory.

Detector components

The central detector system features the giant acrylic sphere instrumented with roughly 18,000 large 20-inch photomultiplier tubes from Hamamatsu Photonics and an additional 25,000 smaller 3-inch tubes for enhanced coverage and calibration. The liquid scintillator is a specially formulated mixture of linear alkylbenzene and gadolinium-loaded compounds to improve neutron capture signals. The surrounding water Cherenkov veto system is instrumented with over 2,000 additional photomultiplier tubes. A sophisticated calibration system, involving automated devices and sources like Americium-241 and Carbon-12, ensures precise energy and position reconstruction. The readout and data acquisition systems are designed to handle the high event rates.

Physics results and prospects

While still under construction, JUNO has already produced technical results from prototype systems and simulation studies, validating its design goals. Projected physics reach indicates it could determine the neutrino mass ordering with a significance greater than 3sigma within six years of data-taking. Its precision on solar mixing parameters is expected to be below 1%. The detector's sensitivity to the diffuse supernova neutrino background could provide a new window into the history of stellar collapses in the universe. Observations of geoneutrinos will offer insights into the Earth's radiogenic heat flow, complementing studies from KamLAND.

Collaboration and funding

The JUNO collaboration is a large international team involving over 70 institutions from countries including China, Italy, Germany, France, Russia, and the United States. Key participating institutes include the Institute of High Energy Physics, the University of the Chinese Academy of Sciences, INFN in Italy, and Max Planck Institute for Physics in Germany. Primary funding is provided by the Chinese Academy of Sciences, the Ministry of Science and Technology of the People's Republic of China, and the National Natural Science Foundation of China. Significant contributions also come from international partners through agencies like the German Research Foundation and the Istituto Nazionale di Fisica Nucleare.

Category:Neutrino experiments Category:Underground laboratories Category:Physics experiments