K2K

K2K (KEK to Kamioka) was an important scientific experiment in Japan that aimed to study neutrinos—tiny, nearly massless particles that rarely interact with matter. In this experiment, a beam of neutrinos was generated at KEK Research Laboratory and sent through the Earth to the Super-Kamiokande detector in Kamioka, about 250 miles away. By comparing how many neutrinos arrived versus how many were expected, scientists confirmed that neutrinos can change types (oscillate), which implies they have mass. K2K provided valuable evidence supporting this phenomenon, advancing our understanding of fundamental particle physics.