The main scientific goal of JUNO is to determine the neutrino mass hierarchy, which refers to the ordering of the masses of the three types of neutrinos. This is crucial for understanding the fundamental properties of neutrinos and for informing theoretical models in particle physics.
JUNO aims to measure the neutrino mass hierarchy by detecting reactor antineutrinos from nuclear power plants located about 53 kilometers away. By precisely measuring the energy spectrum of these antineutrinos, JUNO can observe oscillation patterns that are sensitive to the mass hierarchy.
Besides determining the neutrino mass hierarchy, JUNO has several secondary objectives, including measuring neutrino oscillation parameters with high precision, studying solar neutrinos, supernova neutrinos, and atmospheric neutrinos, and searching for proton decay and other rare processes.
JUNO uses a large liquid scintillator detector, which is a spherical vessel filled with 20,000 tons of liquid scintillator material. This detector is surrounded by approximately 18,000 photomultiplier tubes (PMTs) that detect the light produced when neutrinos interact with the scintillator.
JUNO is expected to start taking data in the mid-2020s. The anticipated operational lifetime of the observatory is at least 20 years, during which it aims to achieve its primary and secondary scientific goals.