This was the first positive measurement of neutrino oscillations in which both the source and detector were fully under experimenters' control.
K2K is a neutrino experiment which directed a beam of muon neutrinos (νμ) from the 12 GeV proton synchrotron at the KEK, located in Tsukuba, Ibaraki, to the Kamioka Observatory, located in Kamioka, Gifu, about 250 km away.
[4] The proton beam from the synchrotron was directed onto an aluminium target, and the resulting collisions produced a copious amount of pions.
[6] The K2K collaboration consisted of roughly 130 physicists from 27 universities and research institutes from all over the world, listed below.
The final K2K results found that at 99.9985% confidence (4.3 σ) there had been a disappearance of muon neutrinos.