Solar neutrino physics at Hyper-Kamiokande
2019 July 22
Hyper-Kamiokande is a multi-purpose next generation neutrino experiment. The detector is a two-layered cylindrical shape ultra-pure water tank, with its height of 60m and diameter of 74 m. The inner detector will be surrounded by 40,000 twenty-inch photosensors to detect water Cherenkov radiation due to the charged particles and provide our fiducial volume of 187 kt. This detection technique is established by Kamiokande and Super-Kamiokande. As the successor of these experiments, Hyper-K will be located deep underground, 650 m below Mt. Nijuugo-yama at Kamioka in Japan to reduce cosmic-ray backgrounds. Besides our physics program with ac- celerator neutrino, atmospheric neutrino and proton decay, neutrino astrophysics is an important research topic for Hyper-K. The sun is an important natural source of neutrinos, and neutrino is almost sole particle which can carry out the information of the solar core. Current observation of solar neutrino is well explained with standard solar model and neutrino oscillation. Though, we still see about 2 sigma discrepancy of neutrino mass squared difference between the solar and reactor experiments. Hyper-K will resolve the problem with large statistics observation. Our solar neutrino observation is also motivated by the detection of He+p neutrino or periodic modulation of the flux. In this presentation, our physics performance with solar neutrino will be discussed.