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      J-PARC Project Newsletter
                                        Special Issue, June 2011
Japan Proton Accelerator Research Complex under operation jointly
by the High Energy Accelerator Research Organization (KEK) and
the Japan Atomic Energy Agency (JAEA)
http://j-parc.jp/index-e.html
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                                                     June 15th, 2011

   INDICATION OF ELECTRON NEUTRINO APPEARANCE AT THE T2K EXPERIMENT

                                                    T2K Collaboration
                   High Energy Accelerator Research Organization (KEK)
           Institute for Cosmic Ray Research, The University of Tokyo
                                                        J-PARC Center


   The T2K experiment, whose primary purpose is to study neutrino
interactions at a large distance from their source, has detected 6
electron neutrino candidate events based on the data collected before
March 11, 2011　when it was interrupted due to the great East Japan
earthquake.  For the first time, it was possible to observe an
indication that muon neutrinos are able to transform into electron
neutrinos over a distance of 295 km through the quantum mechanical
phenomena of neutrino flavor oscillations.　

   The T2K experiment collected about 2% of the original goal of the
total number of events to be collected before the great East Japan
earthquake hit on March 11, 2011. After J-PARC resumes producing muon
neutrinos, which is planned to happen by the end of 2011, the T2K
experiment will continue striving to accumulate the target number of
events to confirm electron neutrino appearance.  The researchers aim
to search for CP violation in leptons to explore the origin of matter
in the universe by upgrading the accelerators at J-PARC to much
higher intensity and enhancing the performance of the detectors.
Electron neutrino appearance is the key to detecting leptonic CP
violation, and the observation result indicates that the T2K
experiment has made a significant step towards this future goal.

   The result was presented at the KEK seminar on June 15 and press
release was issued from KEK/ICRR on the web.

http://www.kek.jp/ja/news/press/2011/J-PARC_T2Kneutrino.html
http://www.kek.jp/intra-e/press/2011/J-PARC_T2Kneutrino.html

   The paper describing the result was submitted to Physical Review
Letters.


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Editorial Board:
Toshifumi TSUKAMOTO (Chair): toshifumi.tsukamoto@kek.jp
Fujio MAEKAWA: maekawa.fujio@jaea.go.jp
Takashi ITO: itou.takashi@jaea.go.jp
Dick MISCHKE (English Editor): mischke@triumf.ca
Chikako KAIBARA (Secretary): kaibara.chikako@jaea.go.jp
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