JUNO Experiment: Current Status and Physics

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kt liquid scintillator (LS) detector under construction 700-m underground in Jiangmen, Guangdong, China, which is expected to be completed in 2023. Its main goal is to determine the neutrino mass ordering (NMO) with the measurement of reactor electron anti-neutrinos from the two adjacent nuclear power plants at a baseline of 53 km. The Taishan Antineutrino Observatory (TAO) detector is located ~30 m from the core of the nuclear power plant, in order to measure the reactor neutrino spectrum, as a reference spectrum for the determination of NMO in JUNO, with resolution better than 2% at 1 MeV. To ensure that the concentration of $^{238}$U and $^{232}$Th in the LS do not exceed the limits for inverse beta decay (IBD) or solar neutrino measurement, the OSIRIS (Online Scintillator Internal Radioactivity Investigation System) pre-detector is installed to monitor the LS of JUNO during the several months of filling. Good sensitivity will be reached for contamination of $^{238}$U/$^{232}$Th, $^{14}$C and $^{210}$Po in the LS. In JUNO, there will be 17,612 20-inch PMTs and 25,600 3-inch PMTs watching at the LS with photocathode coverage of 75.2% and 2.7%, respectively. It is expected that JUNO will have an excellent effective energy resolution of 3% at 1 MeV and an energy nonlinearity uncertainty better than 1%. With 6-years data, the mass ordering can be determined at 3-4σ significant and the precise measurement of oscillation parameters sin$^2θ_{12}$, |∆m$^2_{21}$|, and |∆m$^2_{32}$| will achieve at least 0.6% precision. Besides the main goal, there are many other promising topics of (astro-)particle physics for JUNO. Solar neutrinos will be understood significantly with JUNO’s measurement and the vacuum-matter transition region will be examined. Atmospheric neutrinos measurement will increase the JUNO sensitivity to NMO via a combined analysis. With massive LS, it will be able to detect core-collapse supernova neutrinos of all flavors in multichannels. Low energy threshold down to 10 keV can also be reached for supernova early warning. For the diffuse supernova neutrino background, it is expected to have 2-4 IBD events per year detected with energy above the reactor neutrinos. Geoneutrinos will be detected at a rate of ~400 events per year. The sensitivity of proton decay search will reach 8.34⋅10$^{33}$ years (90% CL) in 10 years of data-taking