In long baseline neutrino oscillation experiments, properties of neutrino are measured with neutrino interaction with the nucleus. Hence, understanding of the neutrino-nucleus interaction is critical for precise measurements of neutrino oscillation parameters. We have been developing a new neutrino detector named WAGASCI, to measure the cross section ratio of neutrino interaction with water and plastic targets with a large angular acceptance at J-PARC. In the T2K experiment, the far detector, Super-Kamiokande, uses water target while the near detectors use mainly plastic target. The uncertainty due to the difference of the target materials is one of major systematic uncertainties in T2K. The target of WAGASCI detector consists of 3-mm thick plastic scintillators assembled into a 3D grid-like structure. Multi-Pixel Photon Counters (MPPCs) are used to detect the light from scintillators. Because of the small light yield from thin scintillators, MPPCs are required to have low crosstalk rate and high photo detection efficiency (PDE).

We will use newly developed, crosstalk-suppression type MPPCs for WAGASCI detector. The new MPPC has an order of magnitude lower dark noise rate and crosstalk rate than old MPPC. We can operate the new MPPC with higher over voltage, which results in higher PDE. The total number of channels will be about 8,000. In order to realize a compact readout of large number of channels, we developed an array type MPPCs that have 32 MPPCs of 1.5 mm diameter active regions with 50 micron pixel size. A measurement system to test a large number of MPPCs is being developed. In this talk, the performance of new MPPC and the result of measurement with mass production will be presented.

The University of Tokyo

Institute for Nuclear Research of the Russian Academy of Sciences, Laboratoire Leprince-Ringuet Ecole Polytechnique, University of Geneva, Kyoto University, Osaka City University, Institute for Cosmic Ray Research