From: Gina Miller (nanogirl@halcyon.com)
Date: Sat Jun 12 1999 - 15:30:43 MDT
Edge Closer to Solving Neutrino Riddle
The first neutrinos have been spotted colliding with heavy water molecules
in a giant tank at the bottom of an Ontario nickel mine. Announced on
Wednesday, the events mark the inauguration of the Sudbury Neutrino
Observatory (SNO), a new facility that physicists hope will finally solve
the solar neutrino problem, which has been haunting the field for decades.
Generated by the sun's nuclear processes, nearly a billion solar
neutrinos--ghostly subatomic particles that can easily pass through Earth
without hitting anything--shower down on each square centimeter of the
planet's surface every second. Although neutrinos come in three "flavors,"
electron, muon, and tau, existing detectors can only see the electron
variety, and they only see half as many as theorists had predicted. To
resolve this discrepancy, physicists have proposed that half of the solar
electron neutrinos switch flavors, or "oscillate," on their way from the
sun's center to Earth. SNO was built to test this theory
The key is its ability to see several varieties of solar neutrinos at once.
SNO contains 1000 tons of ultrapure heavy water, water in which the hydrogen
atoms have been replaced with deuterons, whose nuclei have a proton and a
neutron. When an electron neutrino collides with a heavy water molecule, it
can split apart the neutron and the proton and eject an electron. Other
neutrino flavors split the nuclei but don't scatter electrons. By counting
both neutrons and electrons, SNO should be able to measure both the total
number of incoming neutrinos and the fraction of electron neutrinos, says
physicist and SNO spokesman David Wark of Oxford University, England. If SNO
finds that the shortfall of electron neutrinos is made up in other flavors,
it will provide strong support for oscillations.
"It is an extremely important experiment," agrees physicist Paul Langacker
of the University of Pennsylvania in Philadelphia. "They will very likely
ascertain definitively whether neutrino oscillations are taking place."
Unfortunately, physicists will have to be patient: Neutrinos collide with
matter so rarely that SNO will detect only some 20 neutrinos every day. As a
result, says Wark, "It will be at least a year" before SNO has an answer.
--MARK SINCELL
Gina "Nanogirl" Miller
Nanotechnology Industries
Web:
http://www.nanoindustries.com
E-mail:
nanogirl@halcyon.com
Alternate E-mail
echoz@hotmail.com
"Nanotechnology: solutions for the future."
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