The High Energy Accelerator Research Organization (高エネルギー加速器研究機構 Kō Enerugī Kasokuki Kenkyū Kikō), commonly known as KEK, is a high-energy physics research organization in Tsukuba, Ibaraki Prefecture, Japan. Its two major accelerators are the 12 GeV Proton Synchrotron and the KEKB electron-positron collider where the Belle experiment is currently running.

It also contains the Accelerator Test Facility (ATF) and was the source of the neutrinos studied in the K2K experiment.

KEK is also associated in the J-PARC proton accelerator under construction in Tōkaimura.

(source: Wikipedia)