We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment. With data corresponding to 1.43×10 20 protons on target, we observe 31 fully-contained single µ-like ring events in Super-Kamiokande, compared with an expectation of 104 ± 14 (syst) events without neutrino oscillations. The best-fit point for two-flavor νµ → ντ oscillations is sin 2 (2θ23) = 0.98 and |∆m 2 32 | = 2.65 × 10 −3 eV 2 . The boundary of the 90% confidence region includes the points (sin 2 (2θ23), |∆m 2 32 |) = (1.0, 3.1×10 −3 eV 2 ), (0.84, 2.65×10 −3 eV 2 ) and (1.0, 2.2×10 −3 eV 2 ).

Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision

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The Tokai-to-Kamioka (T2K) experiment is a second generation long baseline neutrino oscillation experiment which aims at a sensitive search for the ν e appearance. The main design features of the T2K near neutrino detectors located at 280 m from the target are presented. Scintillator counters developed for the T2K near detectors are described. Readout of the counters is provided via WLS fibers embedded into S-shape grooves in a scintillator and viewed from both ends by multi-pixel avalanche photodiodes operating in a limited Geiger mode. A description, operational principles and the results of tests of photosensors with a sensitive area of 1.1 mm 2 are presented. A time resolution of 1.5 ns, a spatial resolution of 9.9-12.4 cm, and a MIP detection efficiency of more than 99% were obtained for scintillator detectors in a beam test.