Antimatter Atoms Experiments
Planned
Source: Associated Press
August 10, 2000
GENEVA (AP) - European scientists searching for answers
to some of science's most basic questions announced plans Thursday to
build atoms of antimatter and then ``cage'' them for use in
experiments.
The researchers at the European Laboratory for Particle
Physics, or CERN, said they plan to make atoms of antihydrogen. It
would be the first time that antiatoms have been slowed down enough to
be caught and studied, intensifying global competition between
scientists trying to decode the
mystery of antimatter.
Physicists believe that antimatter is the mirror image
of conventional matter in the universe. For every subatomic particle
in the universe, there appears to be another identical in appearance
and structure, but with its electric or magnetic properties reversed.
Scientists have been puzzling for years over the
disappearance of antimatter. The Big Bang should have created the same
amount of matter and antimatter, and in principle the two should have
wiped each other out.
But somehow there was enough matter left over to create
the universe, and antimatter only exists now in cosmic rays and
particle accelerators.
CERN, famed for its 16 3/4-mile particle accelerator,
this time is using a small decelerator - 616 feet around - to create
its ``antimatter factory.''
The CERN scientists plan to test the antihydrogen atoms
to see if they behave in the same way as ordinary hydrogen.
``We are looking at how the universe would look if it
was made out of antimatter. Would there be the slightest difference
between our universe and the universe of antiatoms?'' said Rolf
Landua, spokesman for one of three projects at CERN looking at the
issue.
If antimatter differs from matter, even by one part in a
hundred billion, that could explain why the world is made up of matter
and why antimatter has disappeared, he added.
The decelerator takes antiprotons - the opposite of
protons- which have been created in the accelerator, groups them
together and then slows them down to a tenth the speed of light.
These can then be captured, either in electromagnetic
fields or by inserting them into ordinary atoms, which is possible
because antiprotons destroy normal protons but not other matter.
Then, positrons - antielectrons emitted by a radioactive
source - are added to the antiprotons. Just as one proton and one
electron creates hydrogen, so one antiproton and one positron creates
antihydrogen.
The antihydrogen is then stored at very low temperatures
and laser beams are shot at it to see if it behaves differently from
hydrogen. Scientists want to know if antiatoms have a slightly
different attraction to each other compared with ordinary atoms.
``We hope to have the first antihydrogen atoms by the
end of this year, and we will then have to construct a new type of
apparatus in order to trap them. We aim to give a first analysis by
the end of 2002,'' Landua said of the project, called ATHENA.
``It could give us a clue to why our universe exists,
but it isn't clear what that clue might be. We ask a question, nature
gives us an answer, and if we're clever enough we understand the
answer.''
The CERN project is one of three major international
efforts trying to solve the mystery of the disappearance of
antimatter. Two projects - BaBar at the
Stanford Linear Accelerator Center in California and Belle, based at
KEK, a Japanese national laboratory - presented their initial results
last week.
Those projects do not aim to build antiatoms, but
instead to measure how antiparticles decay to see how this compares
with the decay of normal particles.
Physicists in the United States said the CERN effort to
manufacture antiatoms is the next step to understanding the
fundamental properties of an antimatter world.
``To really understand whether this mirror world is out
there, you have to test its ingredients and see if they behave the way
we would expect them to behave,'' said Kurt Riesselmann, a physicist
and spokesman for the Fermi National Accelerator Laboratory outside
Chicago.
When they collide, matter and antimatter release
tremendous energy. Some scientists dream of harnessing this energy to
send spacecraft to other solar systems orbiting distant stars.
However, Riesselmann said antimatter propulsion and
other practical applications of the mirror world is a long way off.
The CERN experiments would trap small amounts of antimatter in
magnetic fields for experiments, but that wouldn't be practical on a
larger scale.
``How would you store it?'' he said. ``You couldn't put
it in a vessel or a container made of matter.''
CERN: http://public.web.cern.ch/Public
Antiproton Decelerator:
http://psdoc.web.cern.ch/PSdoc/acc/ad/index.html
ATHENA Project: http://athena.web.cern.ch/athena
BaBar Home Page:
http://www.slac.stanford.edu/BFROOT/index.html
KEK: http://www.kek.jp
By Naomi Koppel
http://dailynews.yahoo.com/h/ap/20000810/sc/antimatter_factory_2.html