Precision Neutrino Oscillation Physics with JUNO

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Neutrinos are among the most ubiquitous and intriguing of the fundamental elementary particles. They have no electric charge and interact only very weakly with the other fundamental particles of nature. They were also long thought to be massless. However, a revolution in our understanding of neutrinos occurred roughly two decades ago with the discovery that these elusive particles change their quantum property known as flavor as they travel through space. This phenomenon, commonly referred to as neutrino oscillation, is now confirmed by a wealth of data and implies that the neutrino must have a mass, even if very small. This award supports the activities of the Jiangmen Underground Neutrino Observatory (JUNO) group at the University of California-Irvine (UCI). The JUNO experiment is primarily designed to provide precision measurements of the interactions of neutrinos produced in reactors at the China Taishan and Yangjiang nuclear power plants. The UCI JUNO team will provide key contributions to the installation and commissioning of the experiment’s small photomultiplier tube (PMT) system and will lead the calibration of the energy response of the full detector. The team is also preparing the data analyses for the first oscillation parameter measurements of the new detector. The program reinitiates the UCI QuarkNet center, including a Masterclass focused on the JUNO experiment, with a primary goal of providing opportunities in particle physics research to high-school teachers and their students with a particular focus on participants from underrepresented groups.JUNO is currently under construction in the southeast of China and is designed to provide a first measurement of the ordering of the neutrino mass states. The detector is scheduled to begin data taking in 2022. The UCI JUNO group is a leader in the project’s small (3-inch) PMT system, consisting of 25,600 photodetectors. Combined with the laser calibration system, the small PMT system is essential to realizing an energy response of the full JUNO detector of 3 percent at 1 MeV and become the first experiment to observe the effect of the “fast” (first and third eigenstates) and “slow” (first and second eigenstates) oscillation frequencies simultaneously. In addition, reaching the detector design energy response will make it possible to measure the oscillation cycles driven by the mass splitting of the second and third eigenstates, and thus discriminate between the two mass ordering scenarios at approximately 3 sigma after 6 years of data taking.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.