Printer Friendly

New pass at neutrino mass.

The first of a new breed of experiments on neutrinos has detected an energy pattern consistent with earlier hints that those subatomic particles have mass. However, the prevailing theory of particle physics assumes no mass for the three types of neutrinos--electron, muon, or tan neutrinos.

Since 1998, experimenters have found that neutrinos can change types--a process possible only if neutrinos have some mass (SN: 12/14/02, p. 371). The scientists have observed such changes among neutrinos emanating from the sun, from cosmic ray collisions with atmospheric molecules, and from nuclear reactors

To generate and measure neutrinos under-more controlled circumstances, researchers in Japan working on the experiment known as K2K have been beaming muon neutrinos through the ground to a detector 250 kilometers away. That work has for the first time measured the particles' initial and final energy distributions.

On June 15 at the Neutrino 2004 meeting in Paris, K2Kphysicist Tsuyoshi Nakaya of Kyoto University reported a deficit of particles at certain energies. The scientists had predicted there would be such a deficit if muon neutrinos became tau neutrinos. K2K provides the first steps toward further accelerator experiments to more precisely pin down aspects of neutrinos.--P.W.
COPYRIGHT 2004 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2004, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Physics
Author:Weiss, P.
Publication:Science News
Article Type:Brief Article
Date:Jun 26, 2004
Previous Article:Cost of protecting the oceans.
Next Article:Sleepy brains take learning seriously.

Related Articles
Weighing the neutrino.
Going back and forth on neutrino oscillations.
Neutrino mass: a tritium disagreement.
Building matter from a dozen blocks.
Putting neutrino detection on ice.
At last, neutrino results from GALLEX.
A Little Mass Goes a Long Way.
Physics Bedrock Cracks, Sun Shines In.
Neutrino shortage may signal new force. (Physics).
Double or nothing: physicists bet the neutrino's its own eerie twin.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters