J-PARC Project Newsletter
                                        Special Issue, July 2013
Japan Proton Accelerator Research Complex under operation jointly by
the High Energy Accelerator Research Organization (KEK) and
the Japan Atomic Energy Agency(JAEA).


                                                              July 19th, 2013


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

   The T2K collaboration announced definitive observation of muon neutrino to
electron neutrino transformation on July 19 at the 2013 European Physical
Society conference on High Energy Physics in Stockholm, Sweden  (
http://eps-hep2013.eu/ ), which was also announced at the press conference
as shown on the web, http://www.kek.jp/ja/NewsRoom/Release/20130719210000/ ,
http://legacy.kek.jp/intra-e/press/2013/071921/ .
In 2011 the collaboration announced the first indication of this process.
Now with 3.5 times more data, an analysis reveals that there are more
electron neutrinos (a total of 28 events) than would be expected (4.6
events) without this new process and this transformation is firmly
established with 7.5 sigma level of significance.

Neutrino oscillation is a manifestation of a long range quantum mechanical
interference.  Observation of this new type of neutrino oscillation leads
the way to new studies of charge-parity
(CP) violation. The T2K experiment expects to collect 10 times more data in
the near future, including data with antineutrino beam for studies of CP
violation in neutrinos.

This discovery was made possible with the unyielding and tireless effort by
the J-PARC staff members and the management to deliver high quality beam to
T2K after the devastating March 2011 earthquake in eastern Japan, which
caused severe damage to the accelerator complex at J-PARC, and abruptly
discontinued the data-taking run of the T2K experiment.

Editorial Board:
Toshifumi TSUKAMOTO (Chair): toshifumi.tsukamoto@kek.jp Kaoru SHIBATA:
shibata.kaoru@jaea.go.jp Takashi ITO: itou.takashi@jaea.go.jp Dick MISCHKE
(English Editor): mischke@triumf.ca Junko BEANBLOSSOM (Secretary):
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