An accelerator complex which gives extremely high-intensity proton beams is being constructed in Tokai, Japan. The project is operated by JAEA (Japan Atomic Energy Agency) and KEK (High Energy Accelerator Research Or- nization) and called J-PARC (Japan Proton Accelerator Research Complex). J-PARC accelerator complex consists of 200MeV linac, 3GeV rapid cycling synchrotron, and 30GeV main synchrotron. The energy of linac will be - tendedto400MeVandtheenergyofthemainringwillbeincreasedto50GeV in the near future. J-PARCaimstoperformvariousresearchesoflifeandmaterialsciencesby using neutron beams from the 3GeV rapid cycling synchrotron. J-PARC also aims to perform various particle and nuclear physics experiments by using the 50GeV main synchrotron. In this book we collected several proposals of particle and nuclear physics experiments to be performed by using 50GeV main synchrotron. Prof. Nagamiya gives a brief introduction of J-PARC. He describes the purpose of the project, the aims of the various facilities, and the researches to be done by using these facilities. Prof. Ichikawa discusses about the long baseline nutrino oscillation expe- ment.
This proposal is called T2K (Tokai to Kamioka) and it aims to measure mixinganglesintheleptonsector.Theytrytoperformaprecisemeasurement of ? by measuring the ? disappearance. Then they go to determine ? by 23 ? 13 measuring ? -? appearance signal. They also search for sterile components ? e by measuring NC events. Prof. Lim discusses about the experiment which searches a very rare decay 0 0 oftheneutralkaon:K ? ? ?? -.ThisdecayoccursviaadirectCPviolation. L Hewillsearchthisdecaymodewithhighersensitivitythanthestandardmodel expectation level.