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Salt helps SNO

A common table commodity is the main ingredient in new measurements by scientists at the Sudbury Neutrino Observatory (SNO). In a presentation Sunday (Sept. 7) at TAUP 2003, a major scientific conference in Seattle, Wash.
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A common table commodity is the main ingredient in new measurements by scientists at the Sudbury Neutrino Observatory (SNO).

In a presentation Sunday (Sept. 7) at TAUP 2003, a major scientific conference in Seattle, Wash., new measurements are reported that strongly confirm the original SNO results announced in 2001 and 2002 that
solved the "Solar Neutrino Problem" and go much further in establishing the properties of neutrinos that cause them to change from one type to another in transit to the Earth from the Sun.

To accomplish the new measurements, the SNO Collaboration added two tonnes of high-purity table salt (NaCl) to the 1,000 tonnes of heavy water at the heart of the detector, sited two kilometers underground in Inco's Creighton Mine.

"We have moved to a precision phase of the measurements," says Queen's University professor Art McDonald, SNO project director through the first two phases of the project.

"These measurements are essential to define a
new theory of elementary particles required to explain finite neutrino masses and their ability to change types. Some of the simplest proposed theories have already been ruled out."

Two-thirds of the electron-type neutrinos produced by nuclear reactions in the core of the Sun are observed to change to muon- or tau-type neutrinos before reaching the Earth.

"These new, solid results are obtained with a 'pinch of salt,' providing three times better sensitivity to the muon and tau neutrinos," says Tony Noble, director of the SNO Institute that administers the project on behalf of an international collaboration of 130 scientists from 15 institutions in Canada, the United States and Britain.

The observations in recent years that neutrinos change from one type to another, implying that they have mass, has led to great interest in the scientific community.

These new findings require a modification of the most basic theories for elementary particles and have provided a strong confirmation that our theories of energy generation in the Sun are very accurate.

New experiments to provide further information on
neutrino properties and the origin of the Dark Matter in the Universe are being developed.

These include projects that could be sited in the new SNOLAB being developed near the SNO underground site.

Such measurements could provide insight into fundamental questions such as why our Universe is composed of matter rather than anti-matter. The answers to such questions require a further understanding of elementary particle theory and further insight into the evolution of the Universe.

To pursue such questions, the Sudbury Neutrino Observatory is about to enter a third experimental phase with new sensitivity.

"We have developed a half-kilometer-long array of ultra-clean detectors to be placed in the heavy water after the salt is removed in September. These detectors are precision instruments that will give us further insight into neutrino properties," says professor Hamish Robertson of the University of Washington, Seattle, American co-spokesman and Interim SNO director for this transition phase.

The new results from the Sudbury Neutrino Observatory (SNO) are posted at http://www.sno.phy.queensu.ca/

The website for the TAUP 2003 conference is http://int.phys.washington.edu/taup2003/.




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