Speaker
Description
Hyper-Kamiokande is a next-generation water Cherenkov detector under construction in Japan. One of the goals of the Hyper-Kamiokande experiment is to measure the CP phase value using the neutrino beam produced at J-PARC. To improve the precision of this measurement, a new water Cherenkov detector (IWCD) is planned to be constructed as a near detector located 1 km downstream from the beam generation point. IWCD will use multi-PMTs which contain 19 3-inch photomultiplier tubes in a vessel with a 50 cm diameter. As the performance of PMT depends on the magnetic field, it is necessary to measure its variation and evaluate its impact on the performance of the reconstruction in IWCD. We measured the effect of geomagnetism on 3-inch photomultiplier tubes. We made a rotating table to change the orientation of the PMT to the geomagnetic field and calculated the detection efficiency, gain, and transit time. According to the result of the measurements, the impacts on the event reconstruction were also estimated using the simulation of IWCD.