Status of the Jiangmen Underground Neutrino Observatory

The Jiangmen Underground Neutrino Observatory (JUNO) is a next generation multipurpose antineutrino detector currently under construction in Jiangmen, China. The central detector, containing 20 kton of a liquid scintillator, will be equipped with ∼18 000 20 inch and 25 600 3 inch photomultiplier tubes. Measuring the reactor antineutrinos of two powerplants at a baseline of 53 km with an unprecedented energy resolution of 3%/√︀E(MeV), the main physics goal is to determine the neutrino mass hierarchy within six years of run time with a significance of 3–4q. Additional physics goals are the measurement of solar neutrinos, geoneutrinos, supernova burst neutrinos, the diffuse supernova neutrino background, and the oscillation parameters sin2 O12, Δm212, and |Δm2ee| with a precision <1%, as well as the search for proton decays. The construction is expected to be completed in 2021.

Scintillation balloon for neutrinoless double-beta decay search with liquid scintillator detectors

Environmental radioactivity is a dominant background for rare decay search experiments, and it is difficult to completely remove such an impurity from detector vessels. We propose a scintillation balloon as the active vessel of a liquid scintillator in order to identify this undesirable radioactivity. According to our feasibility studies, the scintillation balloon enables the bismuth–polonium sequential decay to be tagged with a 99.7% efficiency, assuming a KamLAND-type (KamLAND = Kamioka Liquid scintillator AntiNeutrino Detector) liquid scintillator detector. This tagging of sequential decay using alpha rays from the polonium improves the sensitivity to neutrinoless double-beta decay while rejecting beta ray background from the bismuth.