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MINOS experiment sheds light on mystery of neutrino disappearance (Forwa

Subject: MINOS experiment sheds light on mystery of neutrino disappearance Forwarded
From: Andrew Yee <""ayee \"@">
Date: Fri, 31 Mar 2006 00:17:22 -0500
Newsgroups: sci.astro
Public Affairs
Fermi National Accelerator Laboratory

Press contact:
Kurt Riesselmann, Fermilab Public Affairs

Additional media contacts are listed at the end of the press release.

March 30, 2006


MINOS experiment sheds light on mystery of neutrino disappearance

BATAVIA, Illinois -- An international collaboration of scientists at the Department of Energy's Fermi National Accelerator Laboratory announced today (March 30, 2006) the first results of a new neutrino experiment. Sending a high-intensity beam of muon neutrinos from the lab's site in Batavia, Illinois, to a particle detector in Soudan, Minnesota, scientists observed the disappearance of a significant fraction of these neutrinos. The observation is consistent with an effect known as neutrino oscillation, in which neutrinos change from one kind to another. The Main Injector Neutrino Oscillation Search (MINOS) experiment found a value of delta m2 = 0.0031 eV2, a quantity that plays a crucial role in neutrino oscillations and hence the role of neutrinos in the evolution of the universe.
"Only a year ago we launched the MINOS experiment," said Fermilab
Director Pier Oddone. "It is great to see that the experiment is already
producing important results, shedding new light on the mysteries of the
Nature provides for three types of neutrinos, yet scientists know very
little about these "ghost particles," which can traverse the entire
Earth without interacting with matter. But the abundance of neutrinos in
the universe, produced by stars and nuclear processes, may explain how
galaxies formed and why antimatter has disappeared. Ultimately, these
elusive particles may explain the origin of the neutrons, protons and
electrons that make up all the matter in the world around us.
"Using a man-made beam of neutrinos, MINOS is a great tool to study the
properties of neutrinos in a laboratory-controlled environment," said
Stanford University professor Stan Wojcicki, spokesperson of the
experiment. "Our first result corroborates earlier observations of muon
neutrino disappearance, made by the Japanese Super-Kamiokande and K2K
experiments. Over the next few years, we will collect about fifteen
times more data, yielding more results with higher precision, paving the
way to better understanding this phenomenon. Our current results already
rival the Super-Kamiokande and K2K results in precision."
Neutrinos are hard to detect, and most of the neutrinos traveling the
450 miles from Fermilab to Soudan -- straight through the earth, no
tunnel needed -- leave no signal in the MINOS detector. If neutrinos had
no mass, the particles would not change as they traverse the Earth and
the MINOS detector in Soudan would have recorded 177 +/- 11 muon
neutrinos. Instead, the MINOS collaboration found only 92 muon neutrino
events -- a clear observation of muon neutrino disappearance and hence
neutrino mass. The deficit as a function of energy is consistent with
the hypothesis of neutrino oscilations and yields a value of delta m2,
the square of the mass difference between two different types of
neutrinos, equal to 0.0031 eV2 +/- 0.0006 eV2 (statistical uncertainty)
+/- 0.0001 eV2 (systematic uncertainty). In this scenario, muon
neutrinos can transform into electron neutrinos or tau neutrinos, but
alternative models -- such as neutrino decay and extra dimensions -- are
not yet excluded. It will take the recording of much more data by the
MINOS collaboration to test more precisely the exact nature of the
disappearance process.
Details of the current MINOS results will be presented by David Petyt of
the University of Minnesota at a special seminar at Fermilab on March
30, 2006, at 4:00 p.m. A day later, the MINOS collaboration will
commemorate MINOS co-spokesperson Doug Michael at a memorial service at
Fermilab. Michael, senior research associate at Caltech, died at age 45
on December 25, 2005, after a year-long battle with cancer.
The MINOS experiment includes about 150 scientists, engineers, technical
specialists and students from 32 institutions in 6 countries, including
Brazil, France, Greece, Russia, the United Kingdom and the United
States. The institutions include universities as well as national
laboratories. The U.S. Department of Energy provides the major share of
the funding, with additional funding from the U.S. National Science
Foundation and from the United Kingdom's Particle Physics and Astronomy
Research Council.
"The MINOS experiment is a hugely important step in our quest to
understand neutrinos -- we have created neutrinos in the controlled
environment of an accelerator and watched how they behave over very long
distances," said Professor Keith Mason, CEO of PPARC. "This has told us
that they are not totally massless as was once thought, and opens the
way for a detailed study of their properties. UK scientists have taken
key roles in developing the experiment and in exploiting the data from
it, the results of which will shape the future of this branch of physics."
The Fermilab side of the MINOS experiment consists of a beam line in a
4,000-foot-long tunnel pointing from Fermilab to Soudan. The tunnel
holds the carbon target and beam focusing elements that generate the
neutrinos from protons accelerated by Fermilab's Main Injector
accelerator. A neutrino detector, the MINOS "near detector" located 350
feet below the surface of the Fermilab site, measures the composition
and intensity of the neutrino beam as it leaves the lab. The Soudan side
of the experiment features a huge 6,000-ton particle detector that
measures the properties of the neutrinos after their 450-mile trip to
northern Minnesota. The cavern housing the detector is located half a
mile underground in a former iron mine.
The MINOS neutrino experiment follows up on the K2K long-baseline
neutrino experiment in Japan. From 1999-2001 and 2003-2004, the K2K
experiment in Japan sent neutrinos from an accelerator at the KEK
laboratory to a particle detector in Kamioka, a distance of about 150
miles. Compared to K2K, the MINOS experiment uses a three times longer
distance, and the intensity and the energy of the MINOS neutrino beam
are higher than the K2K beam. These advantages have enabled the MINOS
experiment to observe in less than one year about three times more
neutrinos than the K2K experiment did in about four years.
"It is a great gift for me to hear this news," said Yoji Totsuka, former
spokesperson of the Super-Kamiokande experiment and now Director General
of KEK. "Neutrino oscillation was first established in 1998, with
cosmic-ray data taken by Super-Kamiokande. The phenomenon was then
corroborated by the K2K experiment with a neutrino beam from KEK. Now
MINOS gives firm results in a totally independent experiment. I really
congratulate their great effort to obtain the first result in such a
short time scale."
Fermi National Accelerator Laboratory, founded in 1967, is a Department
of Energy National Laboratory in Batavia, Illinois, about 40 miles west
of Chicago. Fermilab operates the world's highest-energy particle
accelerator, the Tevatron, on its 6,800-acre campus. About 2,300
physicists from universities and laboratories around the world conduct
physics experiments using Fermilab's accelerators to discover what the
universe is made of and how it works. Discoveries at Fermilab have
resulted in remarkable new insights into the nature of the world around
us. Fermilab is operated by Universities Research Association, Inc., a
consortium of 90 research universities, for the United States Department
of Energy, which owns the laboratory.
More information on the MINOS experiment is at

MINOS Institutions:

Argonne National Laboratory
University of Athens (Greece)
Benedictine University
Brookhaven National Laboratory
Cal Tech
University of Cambridge (U.K.)
College de France
Harvard University
Illinois Institute of Technology
Indiana University
Lebedev Physical Institute
Lawrence Livermore National Laboratory
University College, London (U.K.)
University of Minnesota
University of Minnesota-Duluth
Oxford University (U.K.)
University of Pittsburgh
Rutherford Appleton Lab (U.K.)
University of Sao Paulo (Brazil)
Soudan Underground Laboratory
University of South Carolina
Stanford University
University of Sussex (U.K.)
Texas A&M University
University of Texas at Austin
Tufts University
UNICAMP (Brazil)
Western Washington University
University of Wisconsin
College of William and Mary

Media contacts of other InterAction collaboration members available for comment:
Argonne National Laboratory, U.S.A.:
Suraiya Farukhi
Communications and Public Affairs
+ 1 630 2525581

Brookhaven National Laboratory, U.S.A.:
Mona S. Rowe
Media and Communications Office
+ 1 631 3445056

KEK, Japan:
Dr. Youhei Morita
Public Relations Office
+ 81 29 879 6046

Particle Physics and Astronomy Research Council (PPARC), United Kingdom
Peter Barratt
Press and Media Centre
+ 44 1793 442025

For more information on the InterAction collaboration, visit

Photos are available at:

A 12-minute streaming video on the MINOS experiment is at:

Two scientific graphics summarizing the results are at:

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