[en] The BNL-E787/E949 are the experiments to search for the rare decay K⁺ → π⁺νν-bar and to measure |V_td| precisely. The pure CsI calorimeter is used for the high efficiency photon detection. A good resolution is achieved thanks to the high light yield of ∼180 p.e/MeV. Using a pulse analysis performed with the waveform digitizers, the timing resolution of 0.5 ns is achieved. The pulse analysis also provides a good separation of two pulses close in time. (author)

[en] The neutrino facility in the Japan Proton Accelerator Research Complex (J-PARC) produces a very intense neutrino beam for the Tokai to Kamioka long-baseline neutrino oscillation experiment, T2K. The physics operation of the T2K started in January 2010 and the data taken from the January 2010 to March 2011 period correspond to 1.43 × 10"2"0 protons on target. From analysis of these data, the first ν_μ → ν_e appearance candidates were observed and an indication of sin"22θ_1_3 ≠ 0 was obtained with 2.5σ significance. The T2K aims for a very precise measurement of ν_e appearance and a possible search for CP violation with very large statistics. (author)

[en] Magnetic horns for T2K experiment have been developed for these several years. Performances of the horns were tested with prototype version of 1st and 3rd horns. 320 kA operation was succeeded with the prototypes. Endurance tests for the horns revealed some problems, most of which were already resolved. Support modules for horn support were also produced. Schemes to allow remote connection and disconnection of horns were developed

[en] T2K experiment is a next generation neutrino oscillation experiment using 1 MW proton beam and off-axis neutrino beam. The neutrino beamline consists of proton primary beamline where normal-conducting and superconducting magnets are used, secondary beamline (target station including target and horns, decay volume, beam dump and muon monitor) and near neutrino detector. Features and construction status of the beamline are described

[en] Radionuclides, including ³H, ⁷Be, and ²²Na, are produced by high-energy nuclear reactions in the cooling water used to cool magnetic horns at the Japan Proton Accelerator Research Complex (J-PARC) Neutrino Experimental Facility. The origin of each nuclide is discussed by comparing the experimentally determined concentrations with results from PHITS calculations. The chemical behaviour of the radionuclides in water is dependent on the element being considered. Certain nuclides exhibit complex behaviour and become distributed inhomogeneously in the water-circulation system. In particular, ⁷Be nuclides, dominant gamma-ray emitters in the cooling-waters, exist in the water as both water-soluble ions and colloidal species. After passing through the de-ionizer, some amount of ⁷Be remains in the water, mainly as colloidal species. In addition, ⁷Be tends to adsorb on the metal piping and metallic components of the circulation system. The behaviour of ⁷Be contrasts with that of ³H (or T), which exists as tritiated water (HTO) and distributes homogeneously throughout the water cooling system. (authors)