page_title: T2K experiment
section_title: Neutrino beam
hierarchical_section_title: T2K experiment / Neutrino beam
caption_attribution_description: English: The entire view of J-PARC
context_page_description: T2K is a particle physics experiment studying the oscillations of the accelerator neutrinos. The experiment is conducted in Japan by the international cooperation of about 500 physicists and engineers with over 60 research institutions from several countries from Europe, Asia and North America and it is a recognized CERN experiment.
  T2K was the first experiment which observed the appearance of electron neutrinos in muon neutrino beam, it also provided the world best measurement of oscillation parameter θ₂₃ and a hint of a significant matter-antimatter asymmetry in neutrino oscillations. The measurement of the neutrino-antineutrino oscillation asymmetry may bring us closer to the explanation of the existence of our matter-dominated Universe.
  The intense beam of muon neutrinos is produced in the J-PARC facility in Tokai on the east coast of Japan. The beam is directed towards the Super-Kamiokande far detector located 295 km away in the city of Hida, Gifu prefecture. The properties and composition of the neutrino flux are first measured by a system of near detectors located 280 m from the beam production place at the J-PARC site, and then again in the Super-Kamiokande detector.
context_section_description: T2K uses a muon neutrino or muon antineutrino beam produced at the J-PARC facility using a proton beam gradually accelerated to 30 GeV by a system of three accelerators: first to 400 MeV energy by the Linac linear accelerator, then up to 3 GeV by the RCS (Rapid Cycle Synchrotron), and finally up to 30 GeV by the MR synchrotron (Main Ring). Protons collide with a graphite target, producing mesons, mainly pions and kaons, which are then focused by a set of three magnetic horns and directed into a tunnel called the decay volume. Depending on the horns polarity, either positive or negative particles are focused. Positive pions and kaons decay mainly into 
  μ⁺
   and 
  ν
  μ, forming a muon neutrino beam, while negative pions and kaons decay mainly into 
  μ⁻
   and 
  ν
  μ, forming a muon antineutrino beam. All remaining hadrons and charged leptons are stopped by a 75-ton block of graphite (so-called beam dump) and in the ground, while neutrinos travel underground towards the far detector.
caption: Bird's-eye view of the entire facility
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