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This paper reports the track multiplicity and kinematics of muons, charged pions, and protons from charged-current inclusiveν μ and ν μ interactions on a water target, measured using a nuclear emulsion detector in the NINJA experiment. A 3-kg water target was exposed to the T2K antineutrino-enhanced beam corresponding to 7.1 × 10 20 protons on target with a mean energy of 1.3 GeV. Owing to the high granularity of the nuclear emulsion, protons with momenta down to 200 MeV=c from the neutrino-water interactions were detected. We find good agreement between the observed data and model predictions for all kinematic distributions other than the number of charged pions and the muon kinematics shapes. These results demonstrate the capability of measurements with nuclear emulsion to improve neutrino interaction models.

We have carried out νμ charged-current interaction measurement on iron using an emulsion detector exposed to the T2K neutrino beam in the J-PARC neutrino facility. The data samples correspond to 4.0 × 1019 protons on target, and the neutrino mean energy is 1.49 GeV. The emulsion detector is suitable for precision measurements of charged particles produced in neutrino-iron interactions with a low momentum threshold thanks to a thin-layered structure and sub-μm spatial resolution. The charged particles are successfully detected, and their multiplicities are measured using the emulsion detector. The cross section was measured to be σFeCC = (1.28 ± 0.11(stat.)+0.12-0.11(syst.)) × 10-38 cm2/nucleon. The cross section in a limited kinematic phase space of induced muons, θμ < 45° and pμ > 400 MeV/c, on iron was σFeCC phase space= (0.84 ± 0.07(stat.)+0.07-0.06(syst.)) × 10-38 cm2/nucleon. The cross-section results are consistent with previous values obtained via different techniques using the same beamline, and they are reproduced well by current neutrino interaction models. These results demonstrate the capability of the detector in the detailed measurement of neutrino-nucleus interactions around the 1 GeV energy region.

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We describe the first ever implementation of an emulsion multi-stage shifter in an accelerator neutrino experiment. The system was installed in the neutrino monitor building in J-PARC as a part of a test experiment T60 and stable operation was maintained for a total of 126.6 days. By applying time information to emulsion films, various results were obtained. Time resolutions of 5.3 to 14.7 s were evaluated in an operation spanning 46.9 days (time resolved numbers of 3.8-1.4×10 5 ). By using timing and spatial information, a reconstruction of coincident events that consisted of high multiplicity events and vertex events, including neutrino events was performed. Emulsion events were matched to events observed by INGRID, one of near detectors of the T2K experiment, with high reliability (98.5%) and hybrid analysis was established via use of the multi-stage shifter. The results demonstrate that the multi-stage shifter is feasible for use in neutrino experiments.

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