Newspaper article The Christian Science Monitor

Tiny Particle Defies Scientists' Attempts to Determine Mass THE ELUSIVE NEUTRINO

Newspaper article The Christian Science Monitor

Tiny Particle Defies Scientists' Attempts to Determine Mass THE ELUSIVE NEUTRINO

Article excerpt

NATURE'S most elusive form of matter is leading physicists on a merry chase as they try to pin down its properties. Its latest tantalizing "come on" has arisen from the study of its involvement in the radioactive decay of an old batch of uranium salt that the University of Chicago has stored for 33 years.

This will-o'-the-wisp is a fundamental particle called the neutrino. It has no electric charge and zips along at - or nearly at - the speed of light. It interacts so weakly with other particles that it passes through Earth as though the planet were not there.

In fact, more than a billion neutrinos passed harmlessly and unnoticed through your body while you read this sentence.

The question that exercises physicists is whether or not neutrinos have intrinsic mass. They have worked with neutrinos for decades under the assumption that they have no such mass. This assumption is so firmly built into present physical theory that the discovery that at least some forms of neutrinos do have intrinsic mass would render this theory obsolete.

This is the possibility that the uranium salt study now raises. Other lines of research over the past decade have also suggested neutrino mass. But physicists debate their validity.

The new results reinforce the conclusion of these other studies that neutrinos can have mass, even though there is no agreement as to the exact amount of mass that may be involved.

Anthony Turkevich and Thanasis Economou at the University of Chicago, and George Cowan at Los Alamos National Laboratory published the new findings this week in Physical Review Letters.

Briefly put, they found that the radioactive decay of uranium atoms in their old sample proceeded 100 times faster than theory predicts. That theory assumes neutrinos have no mass. This faster decay rate could be explained if neutrinos can have at least a little mass, after all. …

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