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T2K (Tokai to Kamioka, Japan) is a particle physics experiment that is a collaboration between several countries, including Japan, Canada, France, Germany, Italy, South Korea, Poland, Russia, Spain, Switzerland, the United States, and the United Kingdom. It is the second generation follow up to the K2K experiment, a similar long baseline neutrino oscillation experiment. The J-PARC facility produces an intense off-axis beam of muon neutrinos. The beam is directed towards the Super-Kamiokande detector, which is 295 km away. The main goal of T2K is to measure the oscillation of to and to measure the value of ''θ''13, one of the parameters of the Pontecorvo–Maki–Nakagawa–Sakata matrix. On June 15, 2011, the T2K collaboration announced〔http://press.web.cern.ch/press/PressReleases/Releases2010/PR08.10E.html〕 the observation of six electron neutrino-like events compared to an expected background of 1.5, a significance of 2.5 standard deviations. On July 19, 2013, at the European Physical Society meeting in Stockholm, the international T2K collaboration announced a definitive observation of muon neutrino to electron neutrino transformation.〔http://t2k-experiment.org/2013/07/new-results-from-t2k-conclusively-show-muon-neutrinos-transform-to-electron-neutrinos/〕 ==Physics goals== The goal of the T2K experiment is to gain a more complete understanding of neutrino oscillation parameters. Previous neutrino experiments observed the disappearance of muon neutrinos in a beam as they oscillate to tau neutrinos, but oscillation from to was not observed until July 19, 2013. The reason for this is that the mixing angle ''θ''13, that controls the probability for this oscillation, is very small. T2K was the first experiment to measure the appearance of electron neutrinos in a muon neutrino beam. T2K's ND280 detector will take data on neutrino interaction cross section measurements on water. Precise measurements of the other neutrino mixing parameter Δ''m'' and ''θ''23 are another aim of the experiment. Future upgrades to T2K could yield measurement of the CP violation phase ''δ'' by comparing oscillations of neutrinos to those of antineutrinos. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「T2K experiment」の詳細全文を読む スポンサード リンク
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