[News-releases] International Physics Team involving Canadians Sees Hint that Neutrino Mysteries Ready to be Solved

[Tim Meyer]

News Release | For Immediate Release | June 14, 2011, 9:00 p.m. PDT

INTERNATIONAL PHYSICS TEAM INVOLVING CANADIANS SEES HINT THAT NEUTRINO
MYSTERIES READY TO BE SOLVED

(Vancouver, BC) — 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. This data provides an indication for the first time that muon
neutrinos are able to transform into electron neutrinos over a distance of
295 km through the quantum mechanical phenomena of neutrino flavour
oscillations.  These hints validate the premise of the international science
experiment and offer hope that a conclusive understanding of the elusive
neutrino is within reach. 

The Tokai-to-Kamioka (T2K) neutrino experiment publicly announced new
results today which hint that muon neutrinos produced by a particle
accelerator can transform into electron neutrinos as they travel across a
long distance.  The experiment uses a beam of muon neutrinos produced at the
J-PARC accelerator laboratory in eastern Japan.  These neutrinos are beamed
from J-PARC through the Honshu island of Japan to the Super-Kamiokande
neutrino detector 295 km away. A near neutrino detector at J-PARC measures
the beam at its production point to allow a "before and after" comparison
for measurements at Super-Kamiokande.  Previous experiments have shown that
muon neutrinos with similar energies can transform into other kinds of
neutrinos while in transit due to a phenomenon known as "neutrino
oscillation". However, the very low rate at which they turn into electron
neutrinos is an outstanding puzzle in particle physics that is the focus of
a worldwide effort.

Neutrinos, which come in three types, are subatomic particles similar to
electrons but having no electric charge and masses millions of times smaller
than electrons.  They have the unique ability to pass through ordinary
matter without stopping, allowing T2K's beam to actually pass through the
main island of Japan on its way to the detector.  It was once believed that
neutrinos were massless, but results from Super-Kamiokande, Canada’s Sudbury
Neutrino Observatory, and other experiments have established that neutrinos
both have tiny masses and can oscillate from one type to another. This
phenomenon requires modifications to the "Standard Model" of particle
physics, and a major global effort is underway to understand the different
ways in which neutrinos can change type.  Many theorists have suggested that
differences in how neutrinos and antineutrinos oscillate might ultimately
help to explain why our universe is made of matter and not anti-matter.  A
major puzzle is to understand why one type of neutrino, the muon neutrino,
mostly avoids turning into an electron neutrino when it oscillates.

At simultaneous seminars at the host laboratories of KEK and the Institute
of Cosmic Ray Research in Kashiwa, Japan today, T2K announced that, using
all of the T2K data taken before the March 11 earthquake in Japan, they see
six candidate electron neutrino events.  If muon neutrinos didn't change
into electron neutrinos, then T2K should have only seen 1.5 events on
average.  The chance of seeing six or more events when only 1.5 are expected
is less than one percent, suggesting that some of the muon neutrinos are
indeed turning into electron neutrinos, although at a very low rate.

"This is the first time that an experiment looking for this effect has found
a result not consistent with zero," said Professor Scott Oser, spokesperson
for the Canadian contingent of the T2K collaboration. "These results are
very intriguing but not yet conclusive.  Really we need more data to confirm
that this effect is real and not just a statistical fluke.  We're looking
forward to the resumption of data-taking once the process of earthquake
recovery is complete."

The T2K experiment collected about 2% of the original goal of the total
number of events to be collected before the major Japanese 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, as well as pursue the further understanding of this
appearance by combining the neutrino measurements with measurements using
anti-neutrinos, which will shed light on how neutrinos differ from their
antimatter counterparts.  Dr. Mark Hartz from the University of Toronto &
York University will present these results at the Canadian Association of
Physicists annual meeting on Thursday, June 17.  T2K has submitted a
publication describing the new results to the journal Physical Review
Letters.  

The T2K collaboration consists of approximately 500 people from 12 countries
and 59 different institutions.  Canada is one of the largest contributors to
the experiment, with over forty scientists contributing from the University
of Victoria, the University of British Columbia, TRIUMF, the University of
Alberta, the University of Regina, York University, and the University of
Toronto.  The Canadian group has made significant contributions to T2K's
beam line, detectors, beam line monitoring, and analysis.  The central piece
of T2K's near detector and a key beam line monitor were built in Canada and
are now integral parts of the experiment.  T2K uses the concept, developed
at TRIUMF in the 1990s, of an off-axis neutrino beam, in which the beam is
aimed a few degrees away from the detectors in order to get a more
favourable energy spectrum.  T2K is supported in Canada by NSERC, National
Research Council Canada, and the Canada Foundation for Innovation.

###

Media Contacts

Professor Scott Oser
Principal Investigator, T2K Canada	
University of British Columbia
Tel: 604.789.3521
E-mail: oser at phas.ubc.ca

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Timothy I. Meyer, Ph.D.
Head, Strategic Planning & Communications
TRIUMF -- Accelerating Science for Canada |
    Un accélérateur de la démarche scientifique canadienne
4004 Wesbrook Mall
Vancouver, BC  V6T 2A3  CANADA
Tel: 604-222-7674
Fax: 604-222-3791
Cell: 650-464-8955
E-mail: tmeyer at triumf.ca
WWW: http://www.triumf.ca
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