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Independent observations of "neutrino oscillations" have come from an experiment being conducted by Argonne researchers in collaboration with other physicists from the United States and England.
These preliminary findings of the Soudan 2 experiment support the discovery of neutrino oscillations recently announced by researchers at Japan's Super-Kamiokande detector.
Neutrinos are among the most fundamental particle building blocks of matter and may some day provide a unique window on the universe. However, they have been notoriously difficult to study because they rarely interact with ordinary matter. Neutrinos can oscillate -- spontaneously change from one type to another -- only if they have mass. Current theory calls for three types: the electron, muon and tau neutrinos. Past experiments have concluded that all neutrino masses are too small to be measured directly, and may be zero. The oscillation phenomenon allows experiments to probe much smaller masses than can be measured directly.
The discovery of neutrino oscillations could provide a new tool which will dramatically increase physicists' knowledge over the next few years. For example, the current theory of energy and matter in the universe, the "Standard Model," considers neutrinos to be completely massless. Measurements of neutrino masses in oscillation experiments would provide the information needed to expand the Standard Model and shed new light on the nature of mass.
Neutrinos produced by distant stars and galaxies may soon be recorded by "neutrino telescopes" here on Earth, and interpretation of their observations will require a knowledge of oscillations.
Finally, neutrinos produced during evolution of the universe, immediately after the Big Bang, are still all around us. With 300 neutrinos per cubic centimeter everywhere in the universe, even very small neutrino masses could contribute to the "dark matter" problem of cosmology. Small neutrino masses could even have had a profound effect on the early development of the universe itself.
Soudan
The Soudan experiment is a massive particle detector located in a historic iron mine, a half-mile below the rolling hills of northeastern Minnesota. Physicists at both Soudan and Super-Kamiokande (often called Super-K) are studying cosmic-ray neutrinos produced in the earth's atmosphere that travel down through the few thousand feet of rock above the instruments -- and upwards through the 8,000 miles of planet Earth beneath them.
Soudan is the only operating cosmic-ray neutrino detector in the United States. Unlike Super-K, a stainless-steel chamber filled with 12.5 million gallons of water and lined with sensitive light detectors, Soudan comprises 960 tons of iron plates honeycombed with more than 1,500,000 "drift tubes" that detect charged particles.
Although Soudan is much smaller, and therefore observes far fewer neutrino interactions than the Super-K detector, its observations are significant because its design is radically different from the Japanese device. The Soudan detector can measure the directions and energies of incoming neutrinos precisely; this capability can be particularly valuable for the study of oscillations.
The Soudan experiment, named after the small town where the mine is located, has been designed, built and operated by Argonne, the University of Minnesota, Tufts University, and England's Rutherford Appleton Laboratory and Oxford University. The device was designed to determine whether protons, the positively charged particles that make up part of every nucleus in every atom of the universe, will eventually decay into other particles. As the search for proton decay continued, with Soudan and other underground detectors, it soon became apparent that the cosmic-ray neutrino interactions, predicted to be the main background to proton decay, were very different from theoretical predictions.
Although the search for proton decay has so far come up empty, the detectors built to discover it have found plenty of exciting physics to do with cosmic ray neutrinos.
Preliminary findings from the most recent Soudan neutrino studies were presented at Neutrino '98, the same conference that featured the Super-K results. As in their earlier reports, physicists from both groups found fewer "muon" neutrinos than expected, suggesting that some of them had changed into another type, perhaps "tau" neutrinos.
A consistent picture of neutrino oscillations is emerging from the two independent experiments with very different types of detectors. The preliminary Soudan results were reported at the conference, and are available in the proceedings on the World Wide Web at http://www-sk.icrr.u-tokyo.ac.jp/nu98/.
MINOS
Experiments with cosmic ray neutrinos, which originate from cosmic-ray collisions with the earth's atmosphere, can provide only limited information about oscillations. Further progress will require the carefully controlled conditions of an accelerator neutrino beam. Such a beam will soon be built atFermi National Accelerator Laboratory to provide the world's highest intensity source of high energy neutrinos. An experiment using this beam is being designed by high-energy physicists at Argonne, Fermilab and 21 other institutions in the United States, Britain, Russia and China. This experiment, called MINOS (Main Injector Neutrino Oscillation Search), is designed to study in detail the oscillation effects observed at Super-K and Soudan. A new 8,000-ton neutrino detector will be constructed adjacent to the present Soudan detector by Argonne and other MINOS collaborators.
When the MINOS experiment is operating, Fermilab's Main Injector will be used to generate a beam of nearly pure "muon" neutrinos aimed at Soudan, into the ground at a three-degree angle toward the north-northwest. To a neutrino, the intervening 453 miles of solid rock are as transparent as window glass. If neutrinos do oscillate, as the Super-K results indicate, the beam arriving at the underground physics laboratory is expected to create signals indicating a significant number of "tau" neutrinos -- or perhaps some other type produced by oscillations.
The MINOS neutrino beam will be measured by very similar neutrino detectors at Fermilab and Soudan, allowing precise studies of the changes in beam composition caused by oscillations. In addition, these changes can be maximized by adjusting the beam energy. The experiment should be able to confirm the Super-K cosmic-ray results in a very precise way, and also will be able to identify the type of neutrino produced by the oscillations. It is also expected to provide accurate measurements of the difference between the masses of the oscillating neutrino types.
The MINOS experiment is scheduled to begin construction next year and begin taking data in late 2002.
Argonne Credit Union will hold an open house at Argonne-West Friday, July 10.
President Marite Plume and credit union officers will be on site to get acquainted with Argonne-West employees and answer questions about the credit union. Employees will also be able to meet Larry Kurek (OCF), newly elected chairperson of the credit union's board of directors, and Jerry Ward (RPS), representative on the board of directors from Argonne-West.
Information tables will be set up in the foyer of the Laboratory and Office building between 9:30 a.m. and 3:30 p.m. Refreshments will be served, and prizes will be awarded.
Employees can change or simplify their e-mail addresses by visiting a new World Wide Web page at http://www.anl.gov/alias/.
"Any employee can create an e-mail alias -- a simple, easy-to-remember and easy-to-communicate e-mail address -- that is more personal than the actual system address," said Fred Moszur (ECT). "You should create an alias that is distinctive and easy for colleagues or clients to remember."
One example is the Argonne News e-mail address: info@anl.gov.
The alias page, created by Argonne's Electronics and Computing Technologies Division, provides a simple online form that lets employees create and register e-mail aliases. The new web-based interface and its fill-in-the-blank design should enable even novice computer users to register e-mail addresses without requiring a lot of help.
Argonne's intensive recycling efforts have been recognized by the Illinois Recycling Association, which awarded the laboratory an honorable mention in the category of "Outstanding Government Recycling Program."
The Illinois Recycling Association encourages the responsible use of resources by promoting waste reduction, re-use and recycling. It is a statewide association of businesses, government solid waste and recycling coordinators, non-profit organizations, educational institutions and individuals.
The award recognizes the efforts made across all areas of the laboratory. Many different divisions and departments contributed to the various activities identified within the original nomination submitted by Argonne-East's Waste Minimization and Pollution Prevention program, managed withinEMO-WM. Some of the projects recognized by the Illinois Recycling Association were:
* Argonne-East recycled more than 560 tons of mixed office paper, a quarter-million pounds of scrap metal and 17 million pounds of construction and demolition wastes in fiscal year 1997. Combined, these efforts saved the laboratory $128,500 over the cost of disposal.
* More than 87,000 pounds of surplus computer equipment was removed from the waste stream; surplus computer tapes were recycled, and a printer toner cartridge program put in place.
* Fly ash from the laboratory's boiler house is recycled, reducing disposal costs.
* Argonne-East trucks use retread or recapped tires. Refined motor oil and recycled antifreeze are used in laboratory vehicles.
* The laboratory sponsors activities like "America Recycles Day," increasing awareness of recycled products; a forest preserve cleanup day; Earth Day activities, and a "recycled toy drive" benefitting the kids of Chicago's West Garfield Park neighborhood.
The Argonne Guest House is inviting employees to dine outdoors on the terrace during "Grillfest," on Wednesday, June 24, and Thursday, June 25, from 5 p.m. to 8 p.m.
The special dinners feature a selection of seasonal specialties grilled outdoors. Entrees include T-bone of veal, swordfish with corn and cucumber salsa, barbecued salmon, buffalo rib-eye with portobello mushroom sauce, and others. Appetizers and desserts will be available.
Reservations are accepted, but not required: dial 5, then 0, or (630) 739-6000.
Employees and the public are invited to watch the Argonne Amateur Radio Club practice emergency communication techniques at its annual "field day" event at Argonne-East June 27-28.
Argonne's hams will be participating in a national event sponsored by the American Radio Relay League. Amateur radio operators in the U.S. and Canada will be set up "emergency communication stations" and attempt to contact as many other stations as possible. Points are tallied for the number and type of contacts.
The field day will be held at the model aircraft field on Tech Road, starting at noon on June 27 and ending 24 hours later.
