Measurement of neutrino interaction ratio between water and hydrocarbon using a new detector with a 3D grid structure
2018 February 25
2018 June 18
In the T2K experiment, there are systematic errors caused by uncertainties of neutrino-nucleus interaction due to the target difference between a far-detector (water) and near-detector (hydrocarbon). To reduce these errors, we plan to measure the neutrino interaction ratio between water and hydrocarbon with an accuracy better than 3% at J-PARC. A new detector consists of 3D grid-like scintillators to achieve 4π solid angle acceptance. To read out signals, new electronics was developed with the France LLR group. Construction work was finished, and the detector was installed into the T2K near-detector hall. After the installation work, we confirmed that the detector was working very well by using cosmic-rays. Also, we observed well-reconstructed cosmic-muons. We started the neutrino beam measurement in October 2017. We successfully observed neutrino events. The detector is working very stably. The data taking are continued until May 2018, and 8.0×10^20 POT are expected to be accumulated. We expect to observe about 1000 signal events. In this paper, the details of a new detector and the status of the neutrino beam measurement will be reported.