Status and Prospects of the Jiangmen Underground Neutrino Observatory

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment currently under construction in South China, expecting to start data taking in 2023. JUNO primary goal is the determination of the neutrino mass ordering and the measurement, at a sub-percent level, of three of the neutrino oscillation parameters . The main detector, placed in a cavern about 700~m underground (1800 m.w.e.), will consist of 20~kton of liquid scintillator contained in a 35.4~m diameter acrylic sphere, becoming the largest detector of its kind ever built in the world. JUNO will be instrumented with 17,612 20-inch photomultiplier tubes (PMTs), and 25,600 3-inch PMTs reaching a photo-coverage above 75\%. The experiment will achieve an unprecedented energy resolution of $3\%/\sqrt{E(MeV)}$ thanks to a comprehensive calibration system, among others. The acrylic sphere will be submerged in a water Cherenkov detector and covered on the top by layers of plastic scintillator to tag cosmic ray muons, a major source of background. % This paper will review the physics potential of JUNO as a medium baseline reactor antineutrino experiment, illustrate the technical characteristics of the detector, discuss the technological challenges and present the construction status.