Indications of a New Type of Neutrino Oscillation at the T2K Experiment

In the T2K experiment in Japan, a muon neutrino beam was produced in the Japan Proton Accelerator Research Complex, called J-PARC, located in Tokai village, Ibaraki prefecture, on the east coast of Japan, and was aimed at the gigantic Super-Kamiokande underground detector in Kamioka, near the west coast of Japan, 295 km (185 miles) away from Tokai. An analysis of the detected neutrino-induced events in the Super-Kamiokande detector indicates that a very small number of muon neutrinos traveling from Tokai to Kamioka (T2K) transformed themselves into electron neutrinos.

Evidence of this new type of neutrino oscillation may lead the way to new studies of a matter-anti-matter asymmetry called charge-parity (CP) violation. This phenomenon has been observed in quarks (for which Nobel prizes were awarded in 1980 and 2008), but never in neutrinos. CP violation in the early universe may be the reason that the observable universe today is dominated by matter and no significant anti-matter. If the T2K result does indicate this third oscillation, then a search for CP violation in neutrinos will be a major scientific quest in the coming years. Further steps towards this goal will continue to require global scientific collaborations, like T2K, to overcome the significant technical challenges in this search.

The T2K experiment utilizes the J-PARC complex that accelerates protons onto a target to produce an intense secondary particle beam that is focused by special magnets called neutrino horns. The focused particle beam decays into a beam of neutrinos, which is monitored by a neutrino detector 280 meters from the target. This beam of neutrinos travels 295 km underground to be detected in the Super-Kamiokande detector.

The work of the T2K experiment is located in Japan and primarily supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology. However, the experiment was constructed and is operated by an international collaboration, which consists of about 500 physicists from 59 institutions in 12 countries [Japan, US, UK, Italy, Canada, Korea, Switzerland, Spain, Germany, France, Poland, and Russia]. The data collected by the experiment is also analyzed by the collaboration. The US T2K collaborating team of approximately 70 members [Boston University, Brookhaven National Lab, UC Irvine, University of Colorado, Colorado State University, Duke University, Louisiana State University, Stony Brook University, University of Pittsburgh, University of Rochester, and University of Washington (Seattle)] is funded by the US Department of Energy, Office of Science. The US groups have built super-conducting corrector magnets, proton beam monitor electronics, the second neutrino horn and a GPS time synchronization system for the T2K neutrino beamline; and a pi-zero detector and a side muon range detector (partial detector) in the T2K near detector complex. They are also part of the team that built, upgraded and operates the Super-Kamiokande detector.

The March 2011 earthquake in eastern Japan caused damage to the accelerator complex at J-PARC, and the data-taking run of the T2K experiment was abruptly discontinued. Fortunately, however, no scientists working on T2K or technical staff supporting their work were injured in the earthquake or its aftermath. The T2K experiment will be ready to take data when J-PARC resumes its operation, which is planned to occur at the end of 2011.

More details on this measurement have been provided in a press report at http://jnusrv01.kek.jp/public/t2k/ and attached to this document.

Quotes from the T2K US Institutional Representatives:

“It is yet another major step forward in our understanding of the nature of neutrinos and the universe following the remarkable advancements made by the various pioneering neutrino experiments during the last two decades or so. This finding, when confirmed with more data, will provide a more realistic hope for the next generation of experiments to further our knowledge to solve the matter anti-matter asymmetry, which is one of the most profound mysteries in the universe,” said Prof. Chang Kee Jung of Stony Brook University.

“Even though we have studied neutrino oscillations for years, there is still a great thrill in seeing these six events. The neutrino beam technique that we use is working beautifully and the interpretation is simple and direct. I can hardly wait to collect more data. It has been a privilege for all of us at Boston University to participate in this series of experiments in Japan, and we greatly appreciate the efforts at J-PARC and KEK to restart the T2K beam,” said Prof. Ed Kearns of Boston University.

“It took the international collaboration about ten years to realize the project and bring it from first idea to first results. The entire LSU team is honored to be part of the collaboration and proud to contribute to the experiment,” said Thomas Kutter, professor of physics and leader of the T2K project at LSU. “We expect many more results in the near future and look forward to the new research opportunities which are likely to arise from the tantalizing indication of this new neutrino oscillation.”

“Our group at the University of Rochester has been working on this experiment for more than nine years,” said Prof. Kevin McFarland of U. of Rochester. “It has been nothing short of awesome to see a project of this magnitude grow from concepts scrawled on pieces of paper into a working experiment through the work of hundreds of scientists, engineers and technicians.”

“I'm truly impressed by all the hard work each of my fellow collaborators put into the building, running, and analysis of this experiment so that we were able to generate this important first result in a timely fashion,” said Prof. Vittorio Paolone of U. of Pittsburgh.

“If this result is confirmed, it gives a significant boost to the next generation experiments being planned in Japan and the U.S.,” said Prof. Hank Sobel of U. of California, Irvine.

“It is truly an exciting time when the newly built T2K experiment works and finds an indication of the neutrino oscillation effect it was designed and constructed to find. We could have been very unlucky if nature was ornery with no effect to be found or if the Japan earthquake happened earlier before our experiment had enough time to detect the effect,” said Prof. Walter Toki of Colorado State University.

“It's a very exciting time for all of us in T2K who have been working so long to prepare the experiment, and have worked so hard to produce these results. It's especially nice to see the efforts of all of the young people on the experiment and to be around them when the results were known. I think for me, our Duke graduate student Josh Albert said it best: “I'm very excited to have these results made public. Years of effort went into reaching this day, and think we should be very proud of ourselves,” said Prof. Chris Walter of Duke University.

“I am delighted that UW students (two PhD students and three undergraduates) were able to participate in the T2K effort leading to this important new physics result,” said Prof. Jeff Wilkes of U. of Washington.

“This result is a strong indication of the physics T2K sought to discover. With support from all the collaborating institutions and funding agencies, we hope to rebuild the experiment quickly and take more data to see if the result becomes definitive,” said Prof. Eric Zimmerman of U. of Colorado.

Media Contacts:

Prof. Chang Kee Jung, International Co-Spokesperson, T2K Collaboration, Stony Brook University (Stony Brook, NY), chang.jung@stonybrook.edu,

Phone: 631-632-8108 (o), 631-474-4563 (h), 631-707-2018 (c)

Prof. Edward Kearns, Boston University (Boston, MA), kearns@bu.edu,
Phone: 617-353-3425
Prof. Thomas Kutter, Louisiana State University (Baton Rouge, LA), kutter@phys.lsu.edu, Phone: 225-578-8310
Prof. Kevin McFarland, University of Rochester (Rochester, NY), kevin@rochester.edu,

Phone: 775-538-4668, 585-275-7076

Prof. Vittorio Paolone, University of Pittsburgh (Pittsburgh, PA), paolonepitt@gmail.com, Phone: 412- 624–2764

Prof. Hank Sobel, University of California, Irvine (Irvine, CA), hsobel@uci.edu,

Phone: 949- 824-6431

Prof. Walter Toki, Colorado State University (Fort Collin, CO), toki@lamar.colostate.edu, Phone: 970-491-1548

Prof. Chris Walter, Duke University (Durham, NC), chris.walter@duke.edu,
Phone: 919-660-2535
Dr. Peter Wanderer, Brookhaven National Laboratory (Upton, NY), wanderer@bnl.gov

Phone: 631-344-7687

Prof. R. Jeffrey Wilkes, University of Washington (Seattle, WA), wilkes@u.washington.edu, Phone: 206-543-4232

Prof. Eric Zimmerman, University of Colorado (Boulder, CO), edz@Colorado.EDU,
Phone: 303-735-5338