Embargoed until 11 a.m. EST
NSF PR 02-88
- October 29, 2002
Researchers Get First Look into Antimatter Atoms
It seems like the stuff of science fiction, but NSF-sponsored
researchers working at CERN, the European Organization
for Nuclear Research, have probed the properties of
whole atoms of antimatter, the "mirror image" of matter,
for the first time. Their results provide the first
look into the inside of an antimatter atom and are
a big step on the way to testing standard theories
of how the universe operates.
Because of its instability, antimatter is notoriously
hard to handle. Fast-moving or "hot" antimatter has
been created for years, but previous hot anti-atoms
were annihilated by collisions with matter before
they could be studied. Last year the ATRAP (for Antihydrogen
Trap) team led by Gerald Gabrielse of Harvard University,
announced they'd pioneered methods of slowing down
negatively charged antiprotons and combining them
with slow positrons, the positively charged antimatter
equivalent of electrons, to create an environment
for forming the simplest possible anti-atom: antihydrogen.
Now the team has made the first measurements of a complete
antihydrogen atom. The ATRAP team took their hard-won
anti-atoms and ripped them apart with an electric
field. Gabrielse explains "it's like putting the anti-atom
next to a battery. The antiproton would be attracted
to one terminal and the positron would be drawn to
the opposite one." The researchers tweak the electric
field until the atom is torn asunder; the strength
of the field required indicates how tightly the anti-atom
was held together. Their article describing the results
will appear in Physical Review Letters in
These first measurements don't indicate a difference
in the way antihydrogen and hydrogen are put together,
but Gabrielse says to detect differences they'll need
to measure anti-atoms in a more "normal" state.
Although the anti-atoms they've studied move slowly,
their positrons are still excited to unusually high
levels. The researchers' next step is to "de-excite"
the anti-atoms so they can make comparisons to the
physics of normal hydrogen atoms.
According to Gabrielse, almost everyone expects the
properties of hydrogen and antihydrogen to be the
same. Detecting differences, he says, would be "the
biggest discovery in physics in decades" that would
"require scientists to reformulate the most basic
laws of physics".
Current theories predict that the universe could just
as easily be made of antimatter as of matter and don't
explain why our universe is made up exclusively of
the latter. If the researchers find small differences
in the properties of matter and antimatter, they would
contradict the present paradigm and might help solve
the riddle. NSF program manager Denise Caldwell from
the Division of Physics says the ATRAP work is "the
critical first experiment in the search for differences
between matter and antimatter using antihydrogen."
Gabrielse doesn't expect the study of anti-atoms to
yield new applications, but he points out that their
cutting-edge studies have produced technology that
improves everyday life. Magnetic traps used to hold
antiparticles are now used in analyzing pharmaceuticals,
and the superconducting magnets they've patented can
be used in magnetic imaging. As Gabrielse puts it,
"If you push reality really hard, good things always
come out of it."
The National Science Foundation has sponsored the research
leading up to this seminal experiment for 15 years.
Gabrielse is joined in his efforts by ATRAP team members
from Harvard University, the Forschungszentrum Jülich,
CERN, the Max-Planck-Institut für Quantenoptik in
Garching, the Ludwig-Maximilians-Universität in Munich
and York University.
For more about the ATRAP collaborative effort, see: