Neutrinos; Opportunities and Strategies in the Future

Abstract

I try to give an overview of future prospects of the experimental exploration of the unknowns in the neutrino mass pattern and the lepton flavor mixing. Because of the nature of the lectures on which this manuscript is based, I give some pedagogical discussions to prepare for the presentation in the later part. I start from measuring θ_{13} by reactors and accelerators as a prerequisite for proceeding to search for leptonic CP violation. I then discuss how CP violation can be uncovered, and how the neutrino mass hierarchy can be determined. I do these by resolving so called the ``parameter degeneracy'' which is necessary anyway if one wants to seek precision measurement of the lepton mixing parameters. As a concrete setting for resolving the degeneracy I introduce the Tokai-to-Kamioka-Korea two detector complex which receives neutrino superbeam from J-PARC, sometimes dubbed as ``T2KK''. It is shown that T2KK is able to resolve all the eight-fold parameter degeneracy in a wide range of the lepton mixing parameters. I also discuss an alternative way for lifting the θ_{23} octant degeneracy by reactor-accelerator combined method. Finally, I discuss by taking some examples how some theoretically or phenomenologically motivated ideas can be tested experimentally.