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-----Original Message-----
From: Charlotte Allen [SMTP:Charlotte_Allen@PPARC.AC.UK]
Sent: Thursday, June 04, 1998 8:52 AM
To: Multiple recipients of list DISCOVER-INFO
Subject: MASS AND OSCILLATIONS DISCOVERED IN THE ELUSIVE NEUTRINO
THE FOLLOWING RELEASE WAS RECEIVED FROM THE
UNIVERSITY OF HAWAII, IN HONOLULU, AND IS
FORWARDED FOR YOUR INFORMATION.
NOTE THE STRICT "WIRE EMBARGO" - WIRE SERVICES
MAY NOT DISTRIBUTE TO MEDIA CLIENTS UNTIL THE
EMBARGO EXPIRES; AS USUAL, MEDIA MAY NOT
PUBLISH OR BROADCAST UNTIL THE EMBARGO
EXPIRES.
Steve Maran, American Astronomical Society
WIRE EMBARGOED FOR RELEASE: June 4, 8:00 PM
Pacific Daylight Time equals June 5, 12 Noon Japan
Standard Time
MASS AND OSCILLATIONS DISCOVERED IN THE
ELUSIVE NEUTRINO
Contact:John Learned, 808 956-2964,
jgl@uhheph.phys.hawaii.edu, or Cheryl Ernst, 808
956-8856, ernst@hawaii.edu
Additional details and graphics available at
www.phys.hawaii.edu:80/~jgl/
A team of Japanese and American physicists have produced
evidence of mass and oscillations in neutrinos, elementary
particles that individually have the smallest mass yet
collectively may account for much of the mass of the
universe. In a paper to be presented at the Neutrino '98
Conference in Japan on June 5 and submitted to the leading
physics journal, the scientists present evidence that the
ghostly elementary particles called neutrinos do possess
mass and that they alternately change their identities in
time as they travel.
The results come from the first two years of data from
Super-Kamiokande, a $100 million experiment in a
12.5-million-gallon, stainless steel-lined cavity carved out
beneath the Japanese alps, filled with ultra pure water
and observed by 13,000 large area light detectors.
One of the three kinds of neutrinos, the muon flavor, has
been found to and reappear as it travels hundreds of
kilometers through the Earth. The energy and flight distance,
from neutrino production in the atmosphere by cosmic
radiation to the underground instrument, provide a measure
of the difference between neutrino masses. This mass, while
the smallest yet observed for elementary particles, is still
sufficient that the relic neutrinos made in staggering
numbers at the time of the Big Bang, account for much of
the mass of the universe.
"These new results could prove to be the key to finding the
holy grail of
physics, the unified theory," observes University of Hawaii
Professor of
Physics and Astronomy John Learned, one of the authors.
"Neutrinos cannot
now be neglected in the bookkeeping of the mass of the
universe. One only
gets such great data once or twice in a professional lifetime,
maybe
never."
The Super-Kamiokande Collaboration will make a major
statement June 5 at
the Neutrino '98 Conference in Takayama, Japan. (See the
XVIII
International Conference on Neutrino Astrophysics and
Astrophysics web site
at www-sk.icrr.u-tokyo.ac.jp). A paper is being submitted at
the time of
this release to Physical Review Letters, the premier journal
of physics.
The collaboration is led by University of Tokyo's Institute for
Cosmic Ray
Research and includes six U.S. groups (Boston University;
University of
California, Irvine; University of Hawai'i; Louisiana State
University;
State University of New York at Stony Brook; and the
University of
Washington) and eight from Japan (Gifu University, High
Energy Research
Organization (KEK), Kobe University, Niigata University,
Osaka University,
Tohoku University, Tokai University and Tokyo Institute of
Technology) as
well as other collaborators from both countries.
Available: Neutrino discovery Q&A and Timeline, Graphics,
Photo -- 808 956-8856
NEUTRINO DISCOVERY -- A FACT SHEET
THE DETECTOR
The Super-Kamiokande detector is a 50,000-ton
double-layered tank of ultra
pure water observed by 11,146 photomultiplier tubes, each
20 inches in
diameter. The equivalent of an acre of photocathode, it is the
largest
light detection area ever assembled by more than a factor of
ten. Located
in a specially carved out cavity in an old zinc mine 2,000
feet under Mount
Ikena near Kamioka in the Japanese alps, the detector is
reached by driving
through a 2 km-long tunnel. The underground site also
includes a huge
reverse osmosis water filtration system, calibration electron
accelerator,
five trailers of elec\-tronics, the main control room,
preparation areas,
etc.
DATA COLLECTION
The Super-Kamiokande project has been collecting data
since April 1, 1996.
This discovery is based on data collected through January
15, 1998.
Energetic charged elementary particles traveling at close to
the vacuum
speed of light (300,000 km per second) exceed the speed of
light in water.
This results in the optical equivalent of a sonic boom,
Cherenkov
radiation, in which a flash is emitted in a 42-degree
half-angle cone
trailing the particle. This nanosecond directional burst of
blue light is
detected with photomulitpliers. Its pattern, timing and
intensity allow
physicists to determine the particle's direction, energy and
identity.
Data are acquired at a high rate (about 100 triggers per
second), partially
processed and sent via fiber optics to the laboratory outside
the mine,
where they are archived and filtered into different analysis
streams. Most
of the results discussed in the current paper are deduced
from the cases
(two-thirds of the time) when a neutrino produces either a
single electron
or a single muon. These interactions are recorded in the
inner 22.5
kilotons of water about 5.5 times per day.
THE CLAIM
Super-Kamiokande Collaboration claims the discovery of
neutrino mass and
oscillations. The claim is based upon atmospheric neutrino
data, which
resolves an anomaly uncovered in 1985 and confirmed and
elaborated by
subsequent experiments. In its analysis of the present data
base, the team
observed a deficit of muon neutrinos coming from great
distances and at
lower energies; the functional behavior of this deficit
indicates that muon
neutrinos oscillate, thus they have mass.
IMPLICATIONS OF THESE FINDINGS
Oscillations require neutrinos to have mass. Finding
non-zero neutrino mass
is big news for elementary particle physics, requiring
revision of the
Standard Model, which has fit all elementary particle data to
date, but
sets neutrino masses at zero.
The Super-Kamiokande team hopes the insight gained from
the peculiar mixing
observed between neutrinos spurs progress toward a unified
theory that
explains the generations or flavors and predicts particle
masses.
The team also infers that the total mass of neutrinos in the
universe must
be significant--at a minimum amounting to a significant
fraction (10 - 100
percent) of the baryonic mass of the universe and perhaps
representing the
dominant mass in the universe.
In any event, neutrinos cannot now be neglected in the
bookkeeping of the
mass of the universe. Indeed, some theoretical calculations
indicate that
neutrinos may have played a crucial role in the production of
an excess of
matter over anti-matter, and are thus intimately linked to our
very
existence.
Clearly this is the single most important finding about
neutrinos since
their discovery. Some experts call this result the single
most important
result of the decade in elementary particle physics.
THE PHYSICS TEAM
The collaboration team includes about 100 physicists. from
Japan and the
United States.
The lead Japan group is from the University of Tokyo's
Institute for Cosmic
Ray Research, whose director, Professor Yoji Totsuka, is
spokesman for the
collaboration.
Other Japanese institutions are Gifu University, the High
Energy Research
Organization (KEK), Kobe University, Niigata University,
Osaka
University, Tohoku University, Tokai University and Tokyo
Institute of
Technology.
Major U.S. collaborators are from Boston University;
University of
California, Irvine; University of Hawaii; Louisiana State
University; State
University of New York at Stony Brook; and University of
Washington. Other
collaborators are from Brookhaven National Laboratory;
California State
University, Dominguez Hills; Los Alamos National
Laboratory; University of
Maryland and George Mason University.
U.S. team coordinators are Professors Hank Sobel, UC
Irvine (head of the
old Reines neutrino group), and Jim Stone of Boston
University. U.S.
collaborators include many veterans from the IMB
experiment.
________________________________
Charlotte Allen
PPARC Press Office
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North Star Avenue
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Wiltshire
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