Neutrino mass is currently the only sign of new physics beyond the Standard Model (SM) of particle physics. Addressing the remaining unknowns in neutrino physics could provide invaluable clues to fundamental questions. Nuclear reactors have played an active role in neutrino physics since the Savannah River experiment which first detected neutrinos. After the discovery of neutrino oscillation Super-K in 1998, neutrino physicists had soon measured two mixing angles, θ12 and θ23, using atmospheric, accelerator and reactor neutrino sources within ~4 years. However, it took more than 10 years to observe the oscillation effect of the last mixing angle θ13. The Daya Bay Reactor Neutrino Experiment was one of the current generation short-baseline neutrino experiments which have measured the θ13 value successfully. In the first part of this talk, we will start with a brief introduction to neutrino physics then present the Daya Bay reactor neutrino experiment and its latest results.
Thanks to the unexpected large value of θ13 discovered by the short-baseline reactor neutrino experiments and confirmed in the long-baseline oscillation experiments, it is now plausible to resolve neutrino mass hierarchy by observing the interplay effect between oscillations driven by Δm232 and Δm221 at a medium-baseline reactor neutrino experiment. Seizing this opportunity, physicists in China have proposed the Jiangmen Underground Neutrino Observatory (JUNO) to measure the neutrino mass hierarchy utilizing two powerful nuclear power plants Yangjiang and Taishan. The JUNO detector is a 20-kiloton liquid scintillator (LS) detector that will be installed in an underground lab with a 700m rock overburden. Besides its unprecedented target mass for a LS detector, two other key elements essential for the mass hierarchy measurement are its unprecedented ~3%/√E/MeV energy resolution and better than 1% energy scale calibration precision. Such detector performances, together with its optimized baseline (~53km), naturally provide JUNO the capability of measuring Δm232, θ12 and Δm221 to sub-percent precision. The experiment is also an ideal place for observing supernova neutrinos, studying the atmospheric neutrinos, solar neutrinos, geo-neutrinos, and other physics. In the 2nd part of this talk, we will present the design of the JUNO experiment and its detector system, its physics potential, and the current R&D activities to fulfill its ambitious physics goals.