High above the Canadian plains, Japanese and U.S. scientists have
harvested another crop of antimatter particles, in the latest flight
of a balloon-borne experiment named BESS which has flown nearly every
summer since 1993 searching for evidence of an antimatter domain
within our Universe.

BESS (Balloon-borne Experiment with a Superconducting Spectrometer)
lifted off from Lynn Lake in Manitoba, Canada, August 7 at 8:58 p.m.
local time on a 22 hour flight. The 5,300-pound experiment flew
beneath a 40-million-cubic-foot balloon, NASA’s largest, at an
average altitude of approximately 23 miles. BESS was retrieved last
night near Fort McMurray, Alberta, and the team will now begin
sorting through the new data.

Dr. Akira Yamamoto of the High Energy Accelerator Research
Organization in Japan (known as KEK) and Dr. John Mitchell of NASA’s
Goddard Space Flight Center in Greenbelt, Maryland, co-lead this
international experiment, which is jointly sponsored by the Ministry
of Education, Culture, Sports, Science and Technology (MEXT) of Japan
and NASA.

Antimatter particles are forms of matter with electrical charges
exactly the opposite of their ordinary “sister” particles. Whereas a
proton has a positive charge and an electron has a negative charge,
an antiproton has a negative charge and an antielectron (or positron)
has a positive charge. The simplest version of the Big Bang theory
predicts there are equal amounts of matter and antimatter in the
Universe, yet scientists have largely detected only ordinary matter.

BESS contains an instrument that detects a variety of cosmic rays,
which are atomic particles moving through space at nearly the speed
of light. Some of these particles are antiprotons created by
collisions of ordinary matter deep in space. The strong magnetic
field of the BESS superconducting magnet in conjunction with its
high-resolution particle detectors enables a very sensitive search
for antimatter in the Universe.

If BESS were to find a sophisticated form of antimatter, such as an
anti-helium nucleus, it would provide evidence that antimatter
galaxies exist. Anti-helium is virtually impossible to create by any
known process, such as an ordinary particle collision, and would have
to come from a source composed of antimatter.

“It is still a fundamental question why we do not observe antimatter
balancing with matter in the Universe,” said Yamamoto. “We have
actually found no anti-helium in our data taken during the seven
flights from 1993 to 2000, while we have detected seven million
helium nuclei. That fact provides the most direct evidence that our
Galaxy and those nearby are made solely of matter, not antimatter.
Why does nature appear to have not taken the simple path of matter
and antimatter balance?”

Theories have been proposed to explain the apparent dearth of
antimatter in the Universe. Russian physicist Andrei Sakharov
proposed three conditions in 1967 that, if met, would allow a
predominance of matter over antimatter in the early Universe. In the
laboratory setting, physicists have demonstrated that some of these
conditions can be met, but it is not proven that all are met.

As in years past, BESS’ August 2002 catch will likely yield
antiproton cosmic rays among the millions of particles detected. Even
though most of the antiprotons are created as “secondaries” in
well-understood cosmic-ray collisions in deep space, there might be a
chance to detect antiprotons of cosmic-origin such as primordial
black holes that might be created in the very early Universe.

“It would be of extraordinary interest if BESS were to detect
antiprotons in excess of those expected as secondary particles,” said
Mitchell. “There are hints in the current data, but, as always, more
data is needed.”

Balloons offer an inexpensive platform to search for antimatter.
After each yearly flight, the BESS team improves the instrument for
the next flight, resulting in a steadily increasing number of
particles collected. The next BESS flight is anticipated for
Antarctica in December 2003 and January 2004, where scientists hope
to fly the experiment for two weeks continuously, collecting a large
amount of data.

The BESS collaboration includes researchers at NASA Goddard and the
University of Maryland in the United States; and at the High Energy
Accelerator Research Organization, Kobe University, the University of
Tokyo, and the Institute of Space and Astronautical Science, all in

The balloon campaign in Canada is conduced by the National Scientific
Balloon Facility, Palestine, Texas, through the NASA Scientific
Balloon Project Office at Goddard’s Wallops Flight Facility, Wallops
Island, Virginia. In addition to the BESS flight, two flights will be
conducted from Lynn Lake in August for the University of Delaware.

For an image of the BESS payload prior to launch, refer to: