This phenomenon is called the neutrino oscillation and it can occur only when the neutrino carries a mass. In order to pin down this observation at the SuperKamiokande, it is planned at the Joint Project to produce νµ beams from the 50-GeV PS and to measure the νµ flux both at the immediate exit of the accelerator and at the site of SuperKamiokande which is located at a distance of 300 km from the Tokai site. This type of experiment is already conducted at KEK by having νµ beams from the 12-GeV PS. Our Joint Project, however, can produce high-flux neutrino beams with intensity of more than 100 times of the neutrino flux present KEK facility can provide. Thus, a higher accuracy experiment on the origin of the neutrino mass can be done at the Joint Project.

SuperKamiokande Detector

	The author of this article, Dr. Tomofumi NAGAE, is working in Nuclear Physics at KEK, and a member of the Project Office.