Title: The Leptonic Dirac CP Phase from Residual Symmetry and Muon Decay at Rest Experiment

Speaker: Dr. Shao-Feng Ge (葛韶锋) (Max Planck Institute for Nuclear Physics)

Time: 10:00AM, July 25th 2016 (Monday)

Place: Theoretical Physics Division，319

Abstract: With the 1-3 mixing angle measured at reator neutrino experiments, Daya Bay and RENO, there are still three unknown oscillation variables, the neutrino mass hierarchy, the octant of the atmospheric mixing angle, and the leptonic CP phase. Of these three, the CP phase is the most difficult to measure precisely and important for distinguishing flavor symmetries. I will first talk about residual symmetries, which takes the role as low energy effective field theory for neutrino mixing and is analogy of custodial symmetry in the electroweak sector, to predict the CP phase from the measured mixing angles. Then I introduce a new type of neutrino experiment to measure the CP phase. Currently, T2K, NOvA, and DUNE are designed for CP measurement. Nevertheless, they suffer from problems of degeneracy, efficiency, uncertainty, non-unitary mixing and non-standard interaction. All of them can be improved by simply adding a muon decay at rest (muDAR) source to T2(H)K, for example. The same configuration can also apply to next-generation medium baseline reactor neutrino experiments like JUNO and RENO-50, enhancing their physics potential from only mass hierarchy to also CP. With only one source and no extra detectors, this dessign is much better than DAEdLAS which requires 3 sources, but only 20% duty factor and 4 times higher luminosity for each.