T. Koga

The new experiment WAGASCI for water to hydrocarbon neutrino cross section measurement using the J-PARC beam

The T2K (Tokai-to-Kamioka) is a long baseline neutrino experiment designed to study various parameters that rule neutrino oscillations, with an intense beam of muon neutrinos. A near detector complex (ND280) is used to constrain non-oscillated flux and hence to predict the expected number of events in the far detector (Super-Kamiokande). The difference in the target material between the far (water) and near (scintillator, hydrocarbon) detectors leads to the main non-canceling systematic uncertainty for the oscillation analysis. In order to reduce this uncertainty a new water grid and scintillator detector, WAGASCI, has been proposed. The detector will be operated at the J-PARC neutrino beam line with the main physics goal to measure the charged current neutrino cross section ratio between water and hydrocarbon with a few percent accuracy. Further physics program may include high-precision measurements of different charged current neutrino interaction channels. The concept of the new detector will be covered together with the actual construction plan.

W ater/CH Neutrino Cross Section Measurement at J-PARC (WAGASCI Experiment)

T. Koga1, N. Chikuma1, F. Hosomi1, M. Yokoyama1, A. Bonnemaison2, O. Drapier2, O. Ferreira2, M. Gonin2, Th. A. Mueller2, B. Quilain2, I. Aizenberg3, A. Izmaylov3, I. Karpikov3, M. Khabibullin3, A. Khotjantsev3, Y. Kudenko3, S. Martynenko3, A. Mefodiev3, O. Mineev3, T. Ovsjannikova3, S. Suvorov3, N. Yershov3, T. Hayashino4, A. K. Ichikawa4, A. Minamino4, K. Nakamura4, T. Nakaya4, K. Yoshida4, Y. Seiya5, K. Wakamatsu5, K. Yamamoto5, Y. Hayato6 1Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo, Japan 2IN2P3-CNRS, Ecole Polytechnique, Palaiseau, France 3Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia 4Department of Physics,Kyoto University, Kyoto, Japan 5Department of Physics, Osaka City University,Osaka,Japan 6Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo, Kamioka, Japan

First neutrino event detection with nuclear emulsion at J-PARC neutrino beamline

Precise neutrino–nucleus interaction measurements in the sub-multi-GeV region are important to reduce the systematic uncertainty in future neutrino oscillation experiments. Furthermore, an excess of νe interactions, as a possible interpretation of the existence of a sterile neutrino, has been observed in such an energy region. The nuclear emulsion technique can measure all the final state particles with low energy threshold for a variety of targets (Fe, C, H2O, and so on). Its sub- μm position resolution allows measurements of the νe cross-section with good electron/gamma separation capability. We started a new experiment at J-PARC to study sub-multi-GeV neutrino interactions by introducing the nuclear emulsion technique. The J-PARC T60 experiment has been implemented as a first step in such a project. Systematic neutrino event analysis with full scanning data in the nuclear emulsion detector was performed for the first time. The first neutrino event detection and its analysis are described in this paper.

Baby MIND: A magnetised spectrometer for the WAGASCI experiment

The WAGASCI experiment being built at the J-PARC neutrino beam line will measure the ratio of cross sections from neutrinos interacting with a water and scintillator targets, in order to constrain neutrino cross sections, essential for the T2K neutrino oscillation measurements. A prototype Magnetised Iron Neutrino Detector (MIND), called Baby MIND, has been constructed at CERN and will act as a magnetic spectrometer behind the main WAGASCI target. Baby MIND will be installed inside the WAGASCI cavern at J-PARC in the beginning of 2018. Baby MIND will be able to measure the charge and momentum of the outgoing muon from neutrino charged current interactions, to enable full neutrino event reconstruction in WAGASCI. During the summer of 2017, Baby MIND was operated and characterised at the T9 test beam at CERN. Results from this test beam will be presented, including charge identification performance and momentum resolution for charged tracks. These results will be compared to the Monte Carlo simulations. Finally, simulations of charge-current quasi-elastic (CCQE) neutrino interactions in an active scintillator neutrino target, followed by the Baby MIND spectrometer, will be shown to demonstrate the capability of this detector set-up to perform cross-section measurements under different assumptions.

First demonstration of an emulsion multi-stage shifter for accelerator neutrino experiments in J-PARC T60

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

The Baby MIND spectrometer for the J-PARC T59(WAGASCI) experiment

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Baby MIND: A magnetized segmented neutrino detector for the WAGASCI experiment

). 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.

Baby MIND Experiment Construction Status : arXiv

The Baby MIND spectrometer is designed to measure the momentum and charge of muons from neutrino interactions in water and hydrocarbon targets at the J-PARC T59 (WAGASCI) experiment. The WAGASCI experiment will measure the ratio of neutrino charged current interaction cross-sections on water and hydrocarbon aiming at reducing systematic errors in neutrino oscillation analyses at T2K. Construction of the Baby MIND detector within the CERN Neutrino Platform framework was completed in June 2017, where it underwent full commissioning and characterization on a charged particle beam line at the Proton Synchrotron experimental hall.